No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Synchrony of globally invasive Aedes spp. immature mosquitoes along an urban altitudinal gradient in their native range
Abstract
Mosquito-borne infections often have concerted peaks, or are synchronous, across landscapes. This phenomenon might be driven by vector responses to similar environmental conditions that synchronize their abundance. While adult mosquito populations can be synchronous over spatial scales ranging from a few meters to a few kilometers, little to nothing is known about immature mosquito synchrony, including its relationship with mosquito colonization and persistence in larval habitats. Here, we present results from a 2-yearlong synchrony study in co-occurring populations of Aedes (Stegomyia) albopictus (Skuse), Aedes (Stegomyia) flavopictus Yamada and Aedes (Finlaya) japonicus japonicus (Theobald), three invasive mosquito species, along an urban altitudinal gradient in Japan. We found that Ae. albopictus was asynchronous while Ae. flavopictus and Ae. j. japonicus had synchrony that, respectively, tracked geographic and altitudinal patterns of temperature correlation. Spatially, Ae. albopictus was more persistent at hotter locations near urban land use, while Ae. j. japonicus and Ae. flavopictus increasingly persisted farther away from urban land. Temporally, Ae. albopicus and Ae. flavopictus decreased the proportion of colonized habitats following variable rainfall, while Ae. j. japonicus increased with vegetation growth and leptokurtic temperatures. Our results support the hypothesis that immature mosquito synchrony is autonomous from dispersal and driven by common environmental conditions.
... Additional observations of Ae. flavopictus outnumbering Ae. albopictus in Phyllostachys reticulata (Rupr.) bamboo stumps at Utsunomiya city, in Tochigi prefecture ( Kurashige, 1961a , b) and the suggestion that these species might be either having antagonistic interactions or different responses to changing environments ( Chaves, 2016 ), and different synchrony patterns ( Chaves, 2017b ;Chaves et al., 2020 ), highlight the need to understand which environmental conditions modulate the abundance patterns of these two mosquito species. ...
... These differences, in response to landscape variables, on the abundance of these mosquitoes more clearly articulate why urban land use might drive differences in the abundance of Ae. albopictus and Ae. flavopictus , following a pattern similar to what we have observed for both species ovitrap colonization ( Chaves et al., 2020 ). Temporal abundance patterns also suggest both species have a different response to changing thermal environments. ...
Aedes (Stegomyia) albopictus (Skuse) is a major global invasive mosquito species that, in Japan, co-occurs with Aedes (Stegomyia) flavopictus Yamada, a closely related species recently intercepted in Europe. Here, we present results of a detailed 25-month long study where we biweekly sampled pupae and fourth instar larvae of these two species from ovitraps set along Mt. Konpira, Nagasaki, Japan. This setting allowed us to ask whether these species had different responses to changes in environmental variables along the altitudinal gradient of an urban hill. We found that spatially Ae. albopictus abundance decreased, while Ae. flavopictus abundance increased, the further away from urban land. Ae. flavopictus also was more abundant than Ae. albopictus in locations with homogenous vegetation growth with a high mean Enhanced Vegetation Index (EVI), platykurtic EVI, and low SD in canopy cover, while Ae. albopictus was more abundant than Ae. flavopictus in areas with more variable (high SD) canopy cover. Moreover, Ae. flavopictus abundance negatively impacted the spatial abundance of Ae. albopictus. Temporally we found that Ae. flavopictus was more likely to be present in Mt. Konpira at lower temperatures than Ae. albopictus. Our results suggest that spatial and temporal abundance patterns of these two mosquito species are partially driven by their different response to environmental factors.
... One limitation of our study comes from the weather data that we used, based on estimates from a unique point in the Bloomington area (i.e., the Indiana University weather station for temperature and precipitation), and on area estimates for RH. Although beyond the goals of this study, microclimatic heterogeneity and variability might be important to more finely grained patterns of diversity, and such an analysis could be done using weather data from sensors located at the points where mosquitoes were collected or using available remote sensing data that can be linked to the sampled locations (Chaves 2017b, Chaves et al. 2020, In the plot, height indicates the difference in mosquito species composition between locations (i.e., the lower the height, the more similar are species between each pair of locations). The codes in the branches indicate F for the Indiana University Campus Farm and R for the Indiana University Research and Teaching Preserve; numbers 1 to 9 indicate the specific location of the traps, as can be observed in (D) F1 to F4, and (E) R5 to R9 of Fig. 1. 2021). ...
Land use and land cover (LULC) gradients are associated with differences in mosquito species composition and the entomological risk of mosquito-borne disease. Here, we present results from a season-long study of mosquito species richness and abundance with samples collected at 9 locations from 2 plots with contrasting LULC, an urban farm and a forest preserve, in Bloomington, IN, a city in the midwestern USA. With a total sampling effort of 234 trap-nights, we collected 703 mosquitoes from 9 genera and 21 species. On the farm, we collected 15 species (285 mosquitoes). In the preserve, we collected 19 species (418 mosquitoes). Thirteen species were common in both study plots, 2 were exclusive to the farm, and 6 were exclusive to the forest preserve. In both plots, we collected Aedes albopictus and Ae. japonicus. In the farm, the most common mosquito species were Culex restuans/Cx. pipiens and Coquillettidia perturbans. In the preserve, Ae. japonicus and Ae. triseriatus were the 2 most common mosquito species. Time series analysis suggests that weather factors differentially affected mosquito species richness and mosquito abundance in the plots. Temperature, relative humidity (RH), and precipitation were positively associated with richness and abundance at the farm, while increases in the SD of RH decreased both richness and abundance at the preserve. Our results highlight the importance that LULC has for mosquito species diversity and abundance and confirm the presence of Ae. albopictus and Ae. japonicus in southwestern Indiana.
... One challenge to previous studies of spatial synchrony in mosquito populations is the need for relatively long and consistent collection records across disparate geographic locations. The result is that the majority of prior population studies occur over small geographic areas or elevational gradients 8,16,[19][20][21] . However, broadscale spatial synchrony is not uncommon in other insect species. ...
Insects often exhibit irruptive population dynamics determined by environmental conditions. We examine if populations of the Culex tarsalis mosquito, a West Nile virus (WNV) vector, fluctuate synchronously over broad spatial extents and multiple timescales and whether climate drives synchrony in Cx. tarsalis, especially at annual timescales, due to the synchronous influence of temperature, precipitation, and/or humidity. We leveraged mosquito collections across 9 National Ecological Observatory Network (NEON) sites distributed in the interior West and Great Plains region USA over a 45-month period, and associated gridMET climate data. We utilized wavelet phasor mean fields and wavelet linear models to quantify spatial synchrony for mosquitoes and climate and to calculate the importance of climate in explaining Cx. tarsalis synchrony. We also tested whether the strength of spatial synchrony may vary directionally across years. We found significant annual synchrony in Cx. tarsalis, and short-term synchrony during a single period in 2018. Mean minimum temperature was a significant predictor of annual Cx. tarsalis spatial synchrony, and we found a marginally significant decrease in annual Cx. tarsalis synchrony. Significant Cx. tarsalis synchrony during 2018 coincided with an anomalous increase in precipitation. This work provides a valuable step toward understanding broadscale synchrony in a WNV vector.
... Thus we expected mosquito abundance to be associated to both the mean and higher orders of variability, i.e., SD and Kurtosis, of microclimatic variables. We also expected the correlation of mosquito abundance with climatic variables to exhibit a time lag (Hacker et al. 1973;Hayes and Hsi 1975;Reisen et al. 1992;Hoshi et al. 2014bHoshi et al. , 2017Romero et al. 2019;Chaves et al. 2020;Chaves and Friberg 2021). ...
Climate, land use and land cover change influence infectious disease dynamics, particularly vector-borne diseases. Knowledge about mosquito ecology in southern Indiana is limited. Here, we present results from a season long study where we sampled mosquitoes at the Hickory Ridge Fire Tower in Hoosier National Forest, Monroe County, Indiana, USA. Using BG-Pro traps with BG-Lure and LED lights weekly from 23 May to 31 October 2023, we collected 178 mosquitoes over 24 weeks of sampling, encompassing a total of 120 trap-nights, with an average of 1.48 ± 3.41 (SD) mosquitoes per trap-night. The species accumulation curve for all the samples was flat, indicating a comprehensive sampling of species. We collected 10 species with a Chao2 ± SE species richness estimate of 14.46 ± 7.14. The dominant species was Aedes vexans (n = 58, 36%), followed by Culex spp. (composed of morphologically indistinguishable Culex pipiens and Culex restuans) (n = 51, 31%), Culex erraticus (n = 16, 10%), and Aedes triseriatus (n = 15, 9%). Because mosquitoes are ectothermic, they are highly sensitive to microclimatic variables such as temperature, humidity, and rainfall. Our time series analysis showed a significant association of mosquito abundance with the variability (SD and kurtosis) of the environmental variables we studied highlighting the importance of weather fluctuations in mosquito ecology. Our study highlights how weather variability shapes mosquito abundance, thus impacting disease vectors like Culex spp. and Aedes triseriatus with implications for arbovirus transmission in the context of climate change.
... There were 2,070,170 cases notified in Brazil, the highest number of cases in the world [11]. A. aegypti is typical in tropical and subtropical climate regions; its population is associated with climate variations and changes [10,12,13], and dengue fever cases are impacted by accidents [14] and natural and socioeconomic factors [15]. A. aegypti is an insect found in all Brazilian states, and it is responsible for the proliferation of successive dengue fever, Zika virus, chikungunya and yellow fever epidemics in Brazil [16][17][18]. ...
Urban waters (UW) are complex environments, and their definition is related to water systems in urban zones, whether in a natural system or an urban facility. The health of these environments is related to public health and the quality of life because public health is the focal point of environmental and anthropic impacts. Infrastructure is paramount for maintaining public health and social and economic development sanitation. Insufficient infrastructure favors disease vectors. The population and environment suffer from deficient urban water infrastructure in Brazil despite government efforts to manage the existing systems. In this work, machine learning (regression trees) demonstrates the deficiency of sanitation and UW management fragmentation on public health by using the Aedes aegypti infestation index (HI) and water supply, wastewater, stormwater and drainage indicators (SNIS data). The results show that each Brazilian region faces different problems. The more infested regions were Northeastern, Northern and Southeastern. Moreover, municipalities with better SNIS data have lower infestation rates. Minimizing problems related to sanitation through the integrated management of water and urban areas is extremely important in developing countries. UW governance is connected to public health. Water management fragmentation leads to more complex issues, and managers must confront them to improve the quality of life in urban zones.
... In addition, landscape structure is key to facilitating the occurrence of Ae. japonicus, even in a climatically unsuitable region, and vice versa [40]. In general, the presence of Ae. japonicus is more prevalent in vegetation-rich [17,41] and rural areas compared to urban and suburban areas [25] or in the transition zones between forest and settlements [42]. This study also showed a higher probability of finding Ae. japonicus in petrol stations and industrial areas. ...
Background
The expansion of invasive mosquitoes throughout Europe has increased in recent decades. In northern Spain, Aedes albopictus was detected for the first time in 2014, and Aedes japonicus was detected in the three Basque provinces in 2020. This study aimed to evaluate the distribution of these mosquito species and their association with factors related to urbanization.
Methods
In 2021, a total of 568 ovitraps were deployed in 113 sampling sites from 45 municipalities with > 10,000 inhabitants. Oviposition substrate sticks were replaced each fortnight and examined for Aedes eggs from June to November. Aedes eggs were counted, and the eggs from a selection of positive oviposition sticks, encompassing at least one stick from each positive ovitrap, were hatched following their life cycle until the adult stage. When egg hatching was not successful, PCR targeting the COI gene and sequencing of amplicons were carried out.
Results
Eggs were detected in 66.4% of the sampling sites and in 32.4% of the ovitraps distributed in the three provinces of the Basque Country. Aedes albopictus and Ae. japonicus were widespread in the studied area, confirming their presence in 23 and 26 municipalities, respectively. Co-occurrence of both species was observed in 11 municipalities. The analysis of the presence of Aedes invasive mosquitoes and the degree of urbanization (urban, suburban, peri-urban) revealed that Ae. albopictus showed a 4.39 times higher probability of being found in suburban areas than in peri-urban areas, whereas Ae. japonicus had a higher probability of being found in peri-urban areas. Moreover, the presence of Ae. albopictus was significantly associated with municipalities with a higher population density (mean = 2983 inh/km²), whereas Ae. japonicus was associated with lower population density (mean = 1590 inh/km²).
Conclusions
The wide distribution of Ae. albopictus and Ae. japonicus observed confirmed the spread and establishment of these species in northern Spain. A new colonization area of Ae. japonicus in Europe was confirmed. Due to the potential impact of Aedes invasive mosquitoes on public health and according to our results, surveillance programs and control plans should be designed considering different urbanization gradients, types of environments, and population density.
Graphical Abstract
... The difference between the current study and previous ones, however, is that it relied, to our knowledge for the first time, on community science to provide this evidence. The results of the present study also confirm previous findings on Ae. japonicus that showed no association of this species with urbanization, which suggests that this species exploits urban and rural areas equally [11,22]. Neither did the occurrence of Ae. koreicus show a clear association with the level of urbanization, which contrasts with theoretical expectations [23][24][25] and the findings of a recent meta-analysis that showed a negative association between this species and urban environments [10]. ...
Background
Urbanization can be a significant contributor to the spread of invasive mosquito vector species, and the diseases they carry, as urbanized habitats provide access to a great density of food resources (humans and domestic animals) and offer abundant breeding sites for these vectors. Although anthropogenic landscapes are often associated with the presence of invasive mosquito species, we still have little understanding about the relationships between some of these and the built environment.
Methods
This study explores the association between urbanization level and the occurrence of invasive Aedes species, specifically Aedes albopictus, Aedes japonicus, and Aedes koreicus, in Hungary, using data from a community (or citizen) science program undertaken between 2019 and 2022.
Results
The association between each of these species and urbanized landscapes within an extensive geographic area was found to differ. Using the same standardized approach, Ae. albopictus showed a statistically significant and positive relationship with urbanization, whereas Ae. japonicus and Ae. koreicus did not.
Conclusions
The findings highlight the importance of community science to mosquito research, as the data gathered using this approach can be used to make qualitative comparisons between species to explore their ecological requirements.
Graphical Abstract
... They are diseases of poverty and have lacked due attention because they commonly affect the world's poorest populations (Sarkar and Gardner, 2016). A. aegypti is typical in tropical and subtropical climate regions, and its population is associated with climate variations (Chaves et al., 2020;Limper et al., 2016;Moreira et al., 2020;Wilke et al., 2017) and dengue fever cases due to natural and socioeconomic factors (Chen at al., 2020). The mosquito infestation is measured by the A. aegypti Infestation Index Rapid Survey -LIRAa. ...
Public health is at the core of all environmental and anthropic impacts. Urban and territorial planners should include public health concerns in their plans. Basic sanitation infrastructure is essential to maintaining public health and social and economic development. This infrastructure deficiency causes diseases, death and economic losses in developing countries. Framing interconnections among health, sanitation, urbanization and circular economy will assist sustainable development goal achievements. This study aims to identify the relationships between solid waste management indicators in Brazil and the Aedes aegypti mosquito infestation index. Regression trees were employed for modelling due to the complexity and characteristics of the data. The analyses were performed separately from data collected from 3501 municipalities and 42 indicators from the country's five regions. Results show that expenses and personnel indicators were the most critical indicators (in the mid-western, southeastern and southern regions), operational (northeastern (NE) region) and management (northern region). The mean absolute errors ranged from 0.803 (southern region) to 2.507 (NE region). Regional analyses indicate that the municipalities with better SWM results display lower infestation rates in buildings and residences. This research is innovative as it analyses infestation rates rather than dengue prevalence, using a machine learning method, in a multidisciplinary research field that needs further study.
... japonicus eggs in habitats with artificial surfaces (i.e., urban or industrial/transport sites) than in natural and semi-natural areas, which, in our study, were mostly agricultural areas. This is consistent with previous studies from their native range as well as in areas, where this species has been introduced, showing that Ae. japonicus are often encountered in urban areas [45][46][47]. Although they prefer natural habitats to artificial ones, preferably colonizing forested areas, especially forest edges, they have been shown to avoid agricultural areas [48,49]. ...
In Austria, only fragmented information on the occurrence of alien and potentially invasive mosquito species exists. The aim of this study is a nationwide overview on the situation of those mosquitoes in Austria. Using a nationwide uniform protocol for the first time, mosquito eggs were sampled with ovitraps at 45 locations in Austria at weekly intervals from May to October 2020. The sampled eggs were counted and the species were identified by genetic analysis. The Asian tiger mosquito Aedes albopictus was found at two sites, once in Tyrol, where this species has been reported before, and for the first time in the province of Lower Austria, at a motorway rest stop. The Asian bush mosquito Aedes japonicus was widespread in Austria. It was found in all provinces and was the most abundant species in the ovitraps by far. Aedes japonicus was more abundant in the South than in the North and more eggs were found in habitats with artificial surfaces than in (semi-) natural areas. Further, the number of Ae. japonicus eggs increased with higher ambient temperature and decreased with higher wind speed. The results of this study will contribute to a better estimation of the risk of mosquito-borne disease in Austria and will be a useful baseline for a future documentation of changes in the distribution of those species.
... Satellite data have been used to predict life-stagespecific suitable habitats for large areas for some insect vectors such as mosquitoes [10][11][12][13][14][15] by linking satellitederived environmental variables to species occurrence data. This is yet to be fully exploited for tsetse. ...
Background
African trypanosomiasis, which is mainly transmitted by tsetse flies (Glossina spp.), is a threat to public health and a significant hindrance to animal production. Tools that can reduce tsetse densities and interrupt disease transmission exist, but their large-scale deployment is limited by high implementation costs. This is in part limited by the absence of knowledge of breeding sites and dispersal data, and tools that can predict these in the absence of ground-truthing.
Methods
In Kenya, tsetse collections were carried out in 261 randomized points within Shimba Hills National Reserve (SHNR) and villages up to 5 km from the reserve boundary between 2017 and 2019. Considering their limited dispersal rate, we used in situ observations of newly emerged flies that had not had a blood meal (teneral) as a proxy for active breeding locations. We fitted commonly used species distribution models linking teneral and non-teneral tsetse presence with satellite-derived vegetation cover type fractions, greenness, temperature, and soil texture and moisture indices separately for the wet and dry season. Model performance was assessed with area under curve (AUC) statistics, while the maximum sum of sensitivity and specificity was used to classify suitable breeding or foraging sites.
Results
Glossina pallidipes flies were caught in 47% of the 261 traps, with teneral flies accounting for 37% of these traps. Fitted models were more accurate for the teneral flies (AUC = 0.83) as compared to the non-teneral (AUC = 0.73). The probability of teneral fly occurrence increased with woodland fractions but decreased with cropland fractions. During the wet season, the likelihood of teneral flies occurring decreased as silt content increased. Adult tsetse flies were less likely to be trapped in areas with average land surface temperatures below 24 °C. The models predicted that 63% of the potential tsetse breeding area was within the SHNR, but also indicated potential breeding pockets outside the reserve.
Conclusion
Modelling tsetse occurrence data disaggregated by life stages with time series of satellite-derived variables enabled the spatial characterization of potential breeding and foraging sites for G. pallidipes. Our models provide insight into tsetse bionomics and aid in characterising tsetse infestations and thus prioritizing control areas.
Graphical abstract
... We also performed (iii) a synchrony analysis of Ae. aegypti egg counts and the remotely sensed environmental variables based on Landsat 8 and Sentinel 2 images. This is an innovative analysis to study spatio-temporal patterns in mosquito oviposition, which we have previously used to study mosquito larval (Chaves, Friberg, & Moji, 2020) and adult (Chaves, 2017b) abundance patterns. Briefly, a synchrony analysis shows the degree of concerted fluctuation between values of a studied variable, egg counts in this study, as a function of the distance separating the sampling locations (Chaves et al., 2013). ...
Problems with vector surveillance are a major barrier for the effective control of vector-borne disease transmission through Latin America. Here, we present results from a 80-week longitudinal study where Aedes aegypti (L.) (Diptera: Culicidae) ovitraps were monitored weekly at 92 locations in Puntarenas, a coastal city in Costa Rica with syndemic Zika, chikungunya and dengue transmission. We used separate models to investigate the association of either Ae. aegypti-borne arboviral cases or Ae. aegypti egg counts with remotely sensed environmental variables. We also evaluated whether Ae. aegypti-borne arboviral cases were associated with Ae. aegypti egg counts. Using cross-correlation and time series modeling, we found that arboviral cases were not significantly associated with Ae. aegypti egg counts. Through model selection we found that cases had a non-linear response to multi-scale (1-km and 30-m resolution) measurements of temperature standard deviation (SD) with a lag of up to 4 weeks, while simultaneously increasing with finely-grained NDVI (30-m resolution). Meanwhile, median ovitrap Ae. aegypti egg counts increased, and respectively decreased, with temperature SD (1-km resolution) and EVI (30-m resolution) with a lag of 6 weeks. A synchrony analysis showed that egg counts had a travelling wave pattern, with synchrony showing cyclic changes with distance, a pattern not observed in remotely sensed data with 30-m and 10-m resolution. Spatially, using generalized additive models, we found that eggs were more abundant at locations with higher temperatures and where EVI was leptokurtic during the study period. Our results suggest that, in Puntarenas, remotely sensed environmental variables are associated with both Ae. aegypti-borne arbovirus transmission and Ae. aegypti egg counts from ovitraps.
... In that regard, the association between housing quality and malaria transmission is something that could be expected according to Schmalhausen's law, the biological principle stating that biological systems are more sensitive to more unpredictable variables around their mean values [37,79,80]. This type of variability is measured by the kurtosis of a distribution, where platykurtic (a.k.a., low kurtosis distributions) are less likely to have a near constant mean value, as opposed to what is observed in leptokurtic (high kurtosis distributions) where values near the mean are less variable or closer to a constant [17,[81][82][83]. ...
Housing quality has been identified as a key factor for malaria transmission risk. Here, we study the macro-ecological association between housing quality, measured by construction materials, and water access with malaria transmission at the county level in Costa Rica. We used SCAN cluster analysis to identify spatio-temporal clusters of malaria transmission using county level annual malaria records from 1976 to 2018. Data on housing materials and water access collected in the 1973, 1984, 2000 and 2011 national population censuses were analyzed using principal component analysis to derive housing quality and water access indices at the county level. Negative binomial rate generalized linear models, and Akaike Information Criterion (AIC) based model selection, were used to study the association between malaria cases and the percent of houses with metallic roofs, housing quality and water access indices. We found that Malaria was clustered in southern Huétar Caribe Region (Relative Risk, RR = 62.61 for 1990-2008), Huétar Norte Region (RR = 13.73, for 1991-2000) and Puntarenas county (RR = 5.77, for 1995-2002). From 1984 to 2011 most of the counties where malaria was clustered were in the lowest 20th percentile of housing quality in Costa Rica. The regression analysis showed that malaria cases significantly decreased with increasing housing quality at rates that accelerated through time. Our results suggest that housing quality improvement is one among several factors that led Costa Rica to the malaria pre-elimination stage. We propose that housing quality improvement should be considered a component of long-term policies aiming to reduce, or eliminate, major vector-borne and other neglected tropical diseases from Costa Rica, regionally in Mesoamerica, and globally elsewhere.
... To date, we suspect that An. albimanus is the main malaria vector in Cutris and Pocosol districts, but we have been unable to confirm this, because entomological surveillance is currently restricted to mosquito larvae, and the available distribution records for this species and other Anopheles spp. in Costa Rica are not current [6,41]. However, expanding entomological surveillance to adult mosquitoes and testing them for infections could be used as an early warning to trigger reactive case detection, to deploy timely vector control interventions, or even to forecast infection based on weather records and remotelysensed information collected by satellites [42,43]. The CRESS also needs to develop capacities to routinely genotype circulating malaria parasites in humans and mosquitoes, as such information will allow for a better understanding of the propagation of malaria, to recognize whether outbreaks have a clonal structure [44], arising drug resistance, and to better understand the geographic source of parasites in order to coordinate regional efforts for malaria elimination in Mesoamerica and Mexico. ...
Costa Rica is a candidate to eliminate malaria by 2020. The remaining malaria transmission hotspots are located within the Huétar Norte Region (HNR), where 90% of the country's 147 malaria cases have occurred since 2016, following a 33-month period without transmission. Here, we examine changes in transmission with the implementation of a supervised seven-day chloroquine and primaquine treatment (7DCPT). We also evaluate the impact of a focal mass drug administration (MDA) in January 2019 at Boca Arenal, the town in HNR reporting the greatest local transmission. We found that the change to a seven-day treatment protocol, from the prior five-day program, was associated with a 98% reduction in malaria transmission. The MDA helped to reduce transmission, keeping the basic reproduction number, RT, significantly below 1, for at least four months. However, following new imported cases from Nicaragua, autochthonous transmission resumed. Our results highlight the importance of appropriate treatment delivery to reduce malaria transmission, and the challenge that highly mobile populations, if their malaria is not treated, pose to regional elimination efforts in Mesoamerica and México.
Insects often exhibit irruptive population dynamics determined by environmental conditions. Here, we examine if populations of the Culex tarsalis mosquito, an important vector for West Nile virus (WNV), fluctuate synchronously over broad spatial extents and multiple timescales. We also examine whether climate drives synchrony in Cx. tarsalis , especially at annual time scales, due to the synchronous influence of temperature, precipitation, and/or humidity. We leveraged mosquito collections from National Earth Observatory Network (NEON) sites in the USA over a 45-month period, and associated gridMET climate data. We utilized wavelet phasor mean fields and wavelet linear models to quantify spatial synchrony for mosquitoes and climate and to calculate the importance of climate in explaining Cx. tarsalis synchrony. We also tested whether the strength of spatial synchrony may vary directionally across years. We found significant annual synchrony in Cx. tarsalis , and short-term synchrony during a single time period in 2018. Mean minimum temperature was a marginally significant predictor of annual Cx. tarsalis synchrony, and we found a marginally significant decrease in annual Cx. tarsalis synchrony. Significant Cx. tarsalis synchrony during 2018 coincided with an anomalous increase in precipitation. This work provides a valuable step toward understanding broad scale synchrony in a WNV vector.
Quantifying synchrony in species population fluctuations and determining its driving factors can inform multiple aspects of ecological and epidemiological research and policy decisions. We examined seasonal mosquito and arbovirus surveillance data collected in Connecticut, United States from 2001 to 2020 to quantify spatial relationships in 19 mosquito species and 7 arboviruses timeseries accounting for environmental factors such as climate and land cover characteristics. We determined that mosquito collections, on average, were significantly correlated up to 10 km though highly variable among the examined species. Few arboviruses displayed any synchrony and significant maximum correlated distances never exceeded 5 km. After accounting for distance, mixed effects models showed that mosquito or arbovirus identity explained more variance in synchrony estimates than climate or land cover factors. Correlated mosquito collections up to 10-20 km suggest that mosquito control operations for nuisance and disease vectors alike must expand treatment zones to regional scales for operations to have population-level impacts. Species identity matters as well, and some mosquito species will require much larger treatment zones than others. The much shorter correlated detection distances for arboviruses reinforce the notion that focal-level processes drive vector-borne pathogen transmission dynamics and risk of spillover into human populations.
In the last 30 years, various Aedes species were introduced outside their native range. The potentially invasive mosquito species Ae. japonicus was recorded in Europe in 2000 and was found for the first time in Austria in 2011. Within the scope of a mosquito-monitoring program (2014-2019) the range expansion of Ae. japonicus in the province of Burgenland (Austria) was investigated. Throughout the sampling period 130 female Ae. japonicus were collected. The first specimens were captured in 2014 in the southernmost sampling sites. In the following years this species increased its range northwards, on average covering 13.6km/year (sd=20.87). In 2019, its northernmost distribution was in the district Mattersburg, which is located 67.9 km north of the northernmost distribution in 2014 (Güssing). Adults of Ae. japonicus were captured from May to November, with the highest numbers trapped in July and August. The continuative range expansion of this species from the south to the north suggests that this process is driven by natural factors like active dispersal or wind. We found Ae. japonicus not to be very abundant but common in Burgenland. At present, there is no proof that Ae. japonicus is invasive in Austria. More in-depth and long-term investigations of Ae. japonicus are necessary to investigate their interactions with autochthonous species to assess whether this species can become invasive.
Aedes albopictus has originated in Asia and expanded its range worldwide in the last 30 years. In Japan, this species occurs from the Ryukyu islands to Tohoku district, whereas its sibling species Ae. flavopictus is distributed throughout Japan including Hokkaido. On the other hand, the former mainly inhabits residential area, while the latter does natural environments such as bamboo groves and forests. To understand how they differ in habitat use, their performance was compared under various temperature regimes, i.e., constant temperatures of 22, 25 and 28°C and a fluctuating temperature regime of 20–30°C (mean: 25°C). Mortality from the first instar stage to adult emergence was significantly higher in Ae. flavopictus than in Ae. albopictus at constant temperatures of 25 and 28°C. Development time was significantly longer in Ae. flavopictus than in Ae. albopictus at 28°C. The proportion of females that did not oviposit was significantly higher in Ae. flavopictus at a constant temperatures of 28°C and a fluctuating temperature regime. Thus, Ae. albopictus is at least more adapted to higher or fluctuating temperatures than Ae. flavopictus. Such difference in their temperature adaptation may be one of factors that cause their different geographic distribution and habitat use.
The Asian mosquitoes, Aedes albopictus (Skuse) and Aedes japonicus japonicus (Theobald), have invaded North America, Europe, and other regions since the late 20th century. In invasive ranges, Ae. albopictus has well been recognized as urban, domestic species, whereas views about the macrohabitats of Ae. j. japonicus are inconsistent. Previous reports in Japan suggest the disappearance of Ae. j. japonicus from metropolises. However, container-mosquito larvae have not been inspected simultaneously for various macro and microhabitats in metropolises in Japan. The current study in Fukuoka City, a metropolis in southwest Japan, confirmed the absence of Ae. j. japonicus irrespective of macrohabitats (temples with graveyards, shrines, public graveyards, cultivated bamboo groves, and urban forests, all within the area densely inhabited by humans) and microhabitats (container types). In contrast, Ae. albopictus was dominant throughout the macro and microhabitats except forest tree holes rich with competitive species. Past records indicate the disappearance of Ae. j. japonicus from metropolitan Fukuoka within the last 70 yr. Based on careful examination of available evidence, we concluded that 1) both species benefit from human-made environments with artificial containers free from competitors, 2) Ae. j. japonicus disappeared due to hot, dry summer conditions facilitated by urban heat-island effects and a decrease in favored mammal hosts, and 3) Ae. albopictus has proliferated with higher tolerance to hot, dry climate and a wider blood-feeding host-range including humans. This difference is important for efficient control of each species as well as predicting and preventing the expansion into new distribution ranges.
Background:
Aedes aegypti and Aedes albopictus are two globally invasive vectors with similar ecological niches. Encounters between them can result in either competitive exclusion or stable co-existence, but it is unclear what drives these variable outcomes. Larval competition in favor of Ae. albopictus is a main hypothesis for the competitive exclusion of Ae. aegypti observed in some regions. However, the role of oviposition preference in determining the degree of competitive larval interactions in the field is not well understood. In this study, we used a combination of mark-release-recapture methods with ovitraps in the open-field and a semi-field cage to test whether gravid Ae. albopictus seek oviposition sites in response to the presence, species, and density of either conspecific or heterospecific Ae. aegypti larvae in the aquatic habitat. We conducted our study in Medellín, Colombia, where Ae. aegypti is a long-term resident and Ae. albopictus is a recent invader.
Results:
In the open-field and semi-field cage experiments, gravid Ae. albopictus showed strong preference for ovitraps with larvae over those without. They consistently preferred ovitraps with higher density of conspecific (Ae. albopictus) larvae and low density of heterospecific (Ae. aegypti) larvae over traps with no larvae or high density of heterospecific (Ae. aegypti) larvae. In the semi-field cage experiment, traps with low density of Ae. albopictus were not preferred more or less than any other trap, but in the open-field experiment they were preferred over traps without larvae.
Conclusions:
We demonstrate, through open-field and semi-field cage experiments, that Ae. albopictus are more attracted to oviposition sites with larvae and that the combination of species and density of larvae influence attraction. This demonstrated preference could increase interspecific larval competition as Ae. albopictus actively seek containers with conspecific and heterospecific larvae. Any resulting competition with Ae. aegypti may favor one species over the other and alter the distribution or abundance of both. Because these species vary in vectorial capacity and insecticide resistance, effects of interspecific competition could ultimately impact arbovirus transmission rates and the success of vector control efforts .
In June 2019, a single specimen collected at a used tyre company was identified as Aedes flavopictus (Yamada, 1921), a sibling species of Ae. albopictus. Ae. flavopictus has not been recorded outside Japan and South Korea. Although it has only shown dengue virus vector competence under laboratory conditions, its detection demonstrates the value of active surveillance at risk locations and molecular tools for timely intervention against exotic mosquitoes with potential future public health impact.
Dengue continues to be the most important vector-borne viral disease globally and in Brazil, where more than 1.4 million cases and over 500 deaths were reported in 2016. Mosquito control programmes and other interventions have not stopped the alarming trend of increasingly large epidemics in the past few years. Here, we analyzed monthly dengue cases reported in Brazil between 2001 and 2016 to better characterise the key drivers of dengue epidemics. Spatio-temporal analysis revealed recurring travelling waves of disease occurrence. Using wavelet methods, we characterised the average seasonal pattern of dengue in Brazil, which starts in the western states of Acre and Rondônia, then travels eastward to the coast before reaching the northeast of the country. Only two states in the north of Brazil (Roraima and Amapá) did not follow the countrywide pattern and had inconsistent timing of dengue epidemics throughout the study period. We also explored epidemic synchrony and timing of annual dengue cycles in Brazilian regions. Using gravity style models combined with climate factors, we showed that both human mobility and vector ecology contribute to spatial patterns of dengue occurrence. This study offers a characterization of the spatial dynamics of dengue in Brazil and its drivers, which could inform intervention strategies against dengue and other arboviruses.
Early warning systems for vector-borne diseases (VBDs) prediction are an ecological application where data from the interface of several environmental components can be used to predict future VBD transmission. In general, models for early warning systems only consider average environmental conditions ignoring variation in weather variables, despite the prediction from Schmalhausen's law about the importance of environmental variability for biological systems. We present results from a long-term mosquito surveillance program from Harris County, Texas, USA, where we use time series analysis techniques to study the abundance and West Nile virus (WNV) infection patterns in the local primary vector, Culex quinquefasciatus Say. We found that, as predicted by Schmalhausen's law, mosquito abundance was associated with the standard deviation and kurtosis of environmental variables. By contrast, WNV infection rates were associated with 8-month lagged temperature, suggesting environmental conditions during overwintering might be key for WNV amplification during summer outbreaks. Finally, model validation showed that seasonal autoregressive models successfully predicted mosquito WNV infection rates up to 2 months ahead, but did rather poorly at predicting mosquito abundance, a result that might reflect impacts of vector control for mosquito population reduction, geographic scale, and other artifacts generated by operational constraints of mosquito surveillance systems.
Background
In the city of Dar es Salaam, Tanzania, rapid and spontaneous scale-up of window screening occurred through purely horizontal commercial distribution systems without any public subsidies or promotion. Scale-up of window screening coincided with a planned evaluation of programmatic, vertically managed scale-up of regular larvicide application as an intervention against malaria vectors and transmission. We aimed to establish whether scale-up of window screening was associated with suppression of mosquito populations, especially for malaria vectors that strongly prefer humans as their source of blood.
Methods
This study was a re-analysis of a previous observational series of epidemiological data plus new analyses of previously partly reported complementary entomological data, from Dar es Salaam. Between 2004 and 2008, six rounds of cluster-sampled, rolling, cross-sectional parasitological and questionnaire surveys were done in urban Dar es Salaam to assess the effect of larviciding and other determinants of malaria risk, such as use of bed nets and antimalarial drugs, socioeconomic status, age, sex, travel history, mosquito-proofed housing, and spending time outdoors. The effects of scaled-up larvicide application and window screening were estimated by fitting generalised linear mixed models that allowed for both spatial variation between survey locations and temporal autocorrelation within locations. We also conducted continuous longitudinal entomological surveys of outdoor human biting rates by mosquitoes and experimental measurements of mosquito host preferences.
Findings
Best-fit models of Plasmodium falciparum malaria infection prevalence among humans were largely consistent with the results of the previous analyses. Re-analysis of previously reported epidemiological data revealed that most of the empirically fitted downward time trend in P falciparum malaria prevalence over the course of the study (odds ratio [OR] 0·04; 95% CI 0·03–0·06; p<0·0001), which was not previously reported numerically or attributed to any explanatory factor, could be plausibly explained by association with an upward trend in city-wide window screening coverage (OR 0·07; 0·05–0·09; p<0·0001) and progressive rollout of larviciding (OR 0·50; 0·41–0·60; p<0·0001). Increasing coverage of complete window screening was also associated with reduced biting densities of all taxonomic groups of mosquitoes (all p<0·0001), especially the Anopheles gambiae complex (relative rate [RR] 0·23; 95% CI 0·16–0·33) and Anopheles funestus group (RR 0·08; 0·04–0·16), which were confirmed as the most efficient vectors of malaria with strong preferences for humans over cattle. Larviciding was also associated with reduced biting densities of all mosquito taxa (p<0·0001), to an extent that varied consistently with the larvicide targeting scheme and known larval ecology of each taxon.
Interpretation
Community-wide mosquito proofing of houses might deliver greater impacts on vector populations and malaria transmission than previously thought. The spontaneous nature of the scale-up observed here is also encouraging with regards to practicality, acceptability, and affordability in low-income settings.
The bamboo mosquito, Tripteroides bambusa (Yamada) (Diptera: Culicidae), is a common insect across East Asia. Several studies have looked at the ecology of Tr. bambusa developmental stages separately, but little is known about the factors associated with the persistence (how often) and abundance (how many individuals) of Tr. bambusa stages simultaneously studied across a heterogeneous landscape. Here, we ask what environmental and landscape factors are associated with the persistence and abundance of Tr. bambusa stages across the altitudinal gradient of Mt. Konpira, Nagasaki City, Japan. During a season-long study we counted 8065 (7297 4th instar larvae, 670 pupae and 98 adults) Tr. bambusa mosquitoes. We found that persistence and abundance patterns were not associated among stages, with the exception of large (4th instar) and small (1st to 3rd instars) larvae persistence, which were positively correlated. We also found that relative humidity was associated with the persistence of Tr. bambusa aquatic stages, being positively associated with large and small larvae, but negatively with pupae. Similarly, landscape aspect changed from positive to negative the sign of its association with Tr. bambusa pupae and adults, highlighting that environmental associations change with life stage. Meanwhile, Tr. bambusa abundance patterns were negatively impacted by more variable microenvironments, as measured by the negative impacts of kurtosis and standard deviation (SD) of environmental variables, indicating Tr. bambusa thrives in stable environments, suggesting this mosquito species has a finely grained response to environmental changes.
Knowledge about mosquito species diversity at tropical montane cloud forests (TMCFs) in Mesoamerica is scarce. Here, we present data on mosquito species richness from samples biweekly collected, from January to December 2017, in ovitraps installed in a TMCF patch at Vázquez de Coronado County, Costa Rica. Ovitraps were placed at 2.25, 1.50 and 0.75 m at 16 sampling points. During the study period we measured relative humidity and air temperature at each sampling point, and water temperature, volume and pH in each ovitrap. We collected a total of 431 mosquito larvae belonging to five taxonomic units, one identified to the genus level and four to the species level. The most common mosquito species was Culex bihaicolus Dyar & Nuñez Tovar (Diptera: Culicidae), which accounted for nearly 80% (n = 344) of the collected mosquitoes. Culex nigripalpus Theobald (Diptera: Culicidae) was the only medically important species we found and it was collected both in the dry (January to March) and rainy season (April to December). Over 95% (n = 411) of the mosquitoes were collected during the rainy season and 60% (n = 257) at 0.75 m. Among the environmental variables that we measured, only water volume and pH were significantly (P < 0.05) different between the dry and rainy season, the former increasing and the later decreasing during the rainy season. These results suggest that rainfall plays a major role regulating the phenology of the sampled mosquito species and highlight the need to screen for pathogens in Cx. nigripalpus at the study area.
Ecoepidemiological scenarios for Trypanosoma cruzi Chagas transmission are partially shaped by kissing bug vector ecology. The presence of Attalea butyracea Kunth, the ‘royal palm’, is a major risk factor for Chagas disease transmission in Panamá given their frequent infestations by Rhodnius pallescens Barber, a major neotropical T. cruzi vector. It was assumed that in Panamá this relationship was very close and unique, limiting the niche of R. pallescens to that of Att. butyracea. However, here we present observations about T. cruzi-infected R. pallescens infesting coyol palms, Acrocomia aculeata Jacquin, in Pedasí district, Los Santos Province, Panamá. Between May 2015 and August 2016, we sampled kissing bugs from 83 coyol palms using mice-baited traps placed at the crown of each palm during the dry and wet season. We collected 62 R. pallescens and one Eratyrus cuspidatus Stål kissing bugs. Using logistic regression, we found that the probability of kissing bug infestation in coyol palms increased during the rainy season, with infructescence number and palm height. We examined adult R. pallescens bugs (n = 30) and found T. cruzi in 67% of the samples. We were able to isolate and characterize T. cruzi from parasites present in the feces from R. pallescens, all parasites belonging to the TC I lineage. We found that green fronds number and house proximity increased T. cruzi infection probability in kissing bugs collected in coyol palms. These results highlight coyol palms as a potential risk factor for Chagas disease transmission in the dry arch of Panamá.
Mosquito sampling using efficient traps that can assess species diversity and/or presence of dominant vectors is important for understanding the entomological risk of mosquito-borne disease transmission. Here, we present results from a survey of mosquito species sampled with ovitraps in a neotropical rainforest of Costa Rica. We found the method to be an efficient sampling tool. With a total sampling effort of 29 traps, we collected 157 fourth-instar larvae and three pupae belonging to eight mosquito taxonomic units (seven species and individuals from a homogenous taxonomic unit identified to the genus level). In our samples, we found two medically important species, Sabethes chloropterus (Humboldt) and Trichoprosopon digitatum (Rondani). The former is a proven vector of Yellow Fever in sylvatic environments and the later has been found infected with several arboviruses. We also found that mosquito species abundance and diversity increased with canopy cover and in environments where leaf litter dominated the ground cover. Finally, our results suggest that ovitraps have a great potential for systematic sampling in longitudinal and cross-sectional ecological “semi-field” studies in neotropical settings.
The bamboo mosquito, Tripteroides bambusa (Yamada) (Diptera: Culicidae), is a common insect across forested landscapes in Japan. Several studies have reported its overwintering as larvae and eggs, in both natural and artificial water containers. Nevertheless, it is unclear how sensitive this mosquito species is to changes in weather patterns associated with global warming. The El Niño event of 2015 through 2016 was one of the strongest on record and provided an ideal scenario for observations on the overwintering of the bamboo mosquito during a winter predicted to be unusually warm. Thus, we set oviposition traps in mid October 2015 and made weekly observations, from December 2015 to May 2016, on bamboo mosquito larval recruitment and pupation in Nagasaki, Japan. We found that larvae were pupating as late as the first week of January (prior records from the study site indicated mosquito pupation ended by mid-late October) and that pupation resumed in mid April (one month earlier than previous records at the study site). We also found that fourth instar larvae were able to survive in frozen oviposition traps following an extremely unusual snowstorm and cold spell and that recruitment of larvae from eggs happened after this unusual event. Our analysis suggested that overwintering and metamorphosis of the bamboo mosquito is sensitive to average and extreme temperatures, the latter measured by temperature kurtosis. Our results highlight the need to better understand changes in overwintering strategies in insects, and associated trade-offs and impacts on population dynamics, in light of climate change.
The Asian Bush Mosquito, Aedes (Finlaya) japonicus japonicus (Theobald) is an important globally invasive mosquito species. In comparison with other major invasive mosquitoes, relatively little is known about Ae. j. japonicus population dynamics in the field. Here, we present results from a 54-biweek long study of Ae. j. japonicus abundance in ovitraps set across the altitudinal gradient of Mt. Konpira, Nagasaki, Japan. Spatially, we found that Ae. j. japonicus fourth instar larvae (Aj4il) were more abundant at the base and top of Mt. Konpira and in ovitraps with more platykurtic water temperature (WT) distributions. In contrast, we found that temporally Aj4il were more abundant when ovitrap WT was more leptokurtic with 2 weeks of lag, and with high relative humidity SD with 2 months of lag. We also found that Aj4il were unlikely present when ovitrap WT was below 12.41°C. Parameter estimates for the Ricker model suggested that Ae. j. japonicus population growth was under density-dependence regulation, with a stable population dynamics whose fluctuations were associated with changes in ovitrap WT kurtosis and demographic stochasticity. Our results suggest that Aj4il abundance is more sensitive to temperature changes in kurtosis than mean values, potentially limiting the predictive ability of Ae. j. japonicus niche models based on the increase of average temperatures with global warming, and suggesting this mosquito species has a relatively coarse-grained response to temperature changes.
Spatial synchrony, defined as correlated temporal fluctuations among populations, is a fundamental feature of population dynamics, but many aspects of synchrony remain poorly understood. Few studies have examined detailed geographical patterns of synchrony; instead most focus on how synchrony declines with increasing linear distance between locations, making the simplifying assumption that distance decay is isotropic. By synthesising and extending prior work, we show how geography of synchrony, a term which we use to refer to detailed spatial variation in patterns of synchrony, can be leveraged to understand ecological processes including identification of drivers of synchrony, a long-standing challenge. We focus on three main objectives: (1) showing conceptually and theoretically four mechanisms that can generate geographies of synchrony; (2) documenting complex and pronounced geographies of synchrony in two important study systems; and (3) demonstrating a variety of methods capable of revealing the geography of synchrony and, through it, underlying organism ecology. For example, we introduce a new type of network, the synchrony network, the structure of which provides ecological insight. By documenting the importance of geographies of synchrony, advancing conceptual frameworks, and demonstrating powerful methods, we aim to help elevate the geography of synchrony into a mainstream area of study and application.
The bamboo mosquito, Tripteroides bambusa (Yamada) (Diptera: Culicidae), is a mosquito species ubiquitous across forested landscapes in Japan. During 2014 we sampled adult mosquitoes from May to November using a sweep net in Nagasaki, Japan. We recorded and managed our field data using Open Data Kit, which eased the overall process of data management before performing their statistical analysis. Here, we analyse the resulting biweekly time series of the bamboo mosquito abundance using time-series statistical techniques. Specifically, we test for density dependence in the population dynamics fitting the Ricker model. Parameter estimates for the Ricker model suggest that the bamboo mosquito is under density dependence regulation and that its population dynamics is stable. Our data also suggest the bamboo mosquito increased its abundance when temperature was more variable at our study site. Further work is warranted to better understand the linkage between the observed density dependence in the adults and the larvae of this mosquito species.
The dispersal patterns of mosquito vectors are important drivers of vector-borne infectious disease dynamics and understanding movement patterns is pivotal to devise successful intervention strategies. Here, we investigate the dispersal patterns of two globally important mosquito vectors, Aedes albopictus and Culex quinquefasciatus, by marking naturally-occurring larvae with stable isotopes (¹³C or ¹⁵N). Marked individuals were captured with 32 CDC light trap, 32 gravid trap, and 16 BG Sentinel at different locations within two-kilometer radii of six larval habitats enriched with either ¹³C or ¹⁵N. In total, 720 trap nights from July to August 2013 yielded a total of 32,140 Cx. quinquefasciatus and 7,722 Ae. albopictus. Overall, 69 marked female mosquitoes and 24 marked male mosquitoes were captured throughout the study period. The distance that Cx. quinquefasciatus females traveled differed for host-seeking and oviposition-seeking traps, with females seeking oviposition sites traveling further than those seeking hosts. Our analysis suggests that 41% of Cx. quinquefasciatus females that were host-seeking occurred 1–2 kilometer from their respective natal site, while 59% remained within a kilometer of their natal site. In contrast, 59% of Cx. quinquefasciatus females that were seeking oviposition sites occurred between 1–2 kilometer away from their larval habitat, while 15% occurred > 2 kilometer away from their natal site. Our analysis estimated that approximately 100% of Ae. albopictus females remained within 1 km of their respective natal site, with 79% occurring within 250m. In addition, we found that male Ae. albopictus dispersed farther than females, suggesting male-biased dispersal in this Ae. albopictus population. This study provides important insights on the dispersal patterns of two globally relevant vector species, and will be important in planning next generation vector control strategies that mitigate mosquito-borne disease through sterile insect techniques, novel Wolbachia infection, and gene drive strategies.
Patterns of mosquito spatial persistence and temporal presence, as well as synchrony, i.e., the degree of concerted fluctuations in abundance, have been scarcely studied at finely grained spatial scales and over altitudinal gradients. Here, we present a spatial persistence, temporal presence, and synchrony analysis of four common mosquito species across the altitudinal gradient of Mt. Konpira in Nagasaki, Japan. We found that Aedes albopictus (Skuse) was more frequently found at the mountain base. In contrast, Aedes japonicus (Theobald) and Aedes flavopictus Yamada were common higher in the mountain, while Armigeres subalbatus (Coquillet) was uniformly present across the mountain, yet less frequently than the other species during the studied period. Our analysis showed that these spatial heterogeneities were associated with differences in landscape and microclimatic elements of Mt. Konpira. Temporally we found that presence across sampling locations was mainly synchronous across the four species and positively associated with rainfall and temperature. With the exception of Ae albopictus, where no significant synchrony was observed, mosquito species mainly showed flat synchrony profiles in Mt. Konpira when looking at the geographic (2-D) distance between their sampling locations. By contrast, when synchrony was studied across altitude, it was observed that Ae. flavopictus tracked the temperature synchrony pattern, decreasing its synchrony with the separation in altitude between sampling locations. Finally, our results suggest that differences in mosquito species persistence, temporal presence , and synchrony might be useful to understand the entomological risk of vector-borne disease transmission in urban landscapes.
It has been suggested that climate change may have facilitated the global expansion of invasive disease vectors, since several species have expanded their range as temperatures have warmed. Here, we present results from observations on two major global invasive mosquito vectors (Diptera: Culicidae), Aedes albopictus (Skuse) and Aedes japonicus (Theobald), across the altitudinal range of Mt. Konpira, Nagasaki, Japan, a location within their native range, where Aedes flavopictus Yamada, formerly a rare species, has now become dominant. Spatial abundance patterns of the three species suggest that temperature is an important factor influencing their adult distribution across the altitudinal range of Mt. Konpira. Temporal abundance patterns, by contrast, were associated with rainfall and showed signals of density-dependent regulation in the three species. The spatial and temporal analysis of abundance patterns showed that Ae. flavopictus and Ae. albopictus were negatively associated, even when accounting for differential impacts of weather and other environmental factors in their co-occurrence patterns. Our results highlight a contingency in the expansion of invasive vectors, the potential emergence of changes in their interactions with species in their native communities, and raise the question of whether these changes might be useful to predict the emergence of future invasive vectors.
Zika virus, already widely distributed in Africa and Asia, was recently reported in two Northeastern Brazilian: State of Bahia and State of Rio Grande do Norte, and one Southeastern: State of São Paulo. This finding adds a potentially noxious virus to a list of several other viruses that are widely transmitted by Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus in Brazil. The pathology and epidemiology, including the distribution and vectors associated with Zika virus, are reviewed. This review is focused on viruses transmitted by Aedes (Stegomyia) mosquitoes, including dengue, Chikungunya, Zika, Mayaro, and yellow fever virus, to emphasize the risks of occurrence for these arboviruses in Brazil and neighboring countries. Other species of Aedes (Stegomyia) are discussed, emphasizing their involvement in arbovirus transmission and the possibility of adaptation to environments modified by human activities and introduction in Brazil.
The seasonal and spatial variations of mosquito communities in tree holes were examined on a small hill in Nagasaki, Japan. Thirty-one tree holes were examined 17 times from October, 1988 to October, 1989. The following 8 species of mosquito larvae were identified : Tripteroides bambusa, Uranotaenia novobscura, Aedes japonicus, Ae. albopictus, Armigeres subalbatus, Culex kyotoensis, Orthopodomyia anopheloides and Ae. nipponicus. A variance test for species association suggested a strong negative association among tree hole mosquitoes. The relationship between tree hole properties and community structure was analyzed to discover what type of tree holes is most commonly occupied by Ae. albopictus and other mosquitoes. Two groups of tree holes were identified by comparing species composition among tree holes based on the Trellis diagram. Comparison of the incidence of tree hole mosquitoes and the physical properties of tree holes in the 2 groups suggested that "open-type" and drought-resisting tree holes having the following properties are most preferable for Ae. albopictus : the hole was top-opening, large in volume and in size of the opening and the surface of standing water was easily detected from the above.
Significance
Persons living in the tropics and subtropics are at risk for dengue fever and dengue hemorrhagic fever, and large epidemics occur unexpectedly that can overburden healthcare systems. The spatial and temporal dynamics of dengue transmission are poorly understood, limiting disease control efforts. We compiled a large-scale dataset and analyzed continental-scale patterns of dengue in Southeast Asia. Our analysis shows that periods of elevated temperatures can drive the occurrence of synchronous dengue epidemics across the region. This multicountry collaborative study improved insight that may lead to improved prediction of dengue transmission patterns and more effective disease surveillance and control efforts.
Understanding the impacts of weather fluctuations, and environmental gradients, on the abundance of vectors is fundamental to grasp the dynamic nature of the entomological risk for disease transmission. The mosquito
Armigeres subalbatus
(Coquillet) is a common vector of filariasis. Nevertheless, its population dynamics have been relatively poorly studied. Here, we present results from a season long study where we studied spatio-temporal abundance patterns of
Ar. subalbatus
across the altitudinal gradient of Mt. Konpira in Nagasaki, Japan. Spatially, we found that abundance of adult
Ar. subalbatus
decreased with altitude and increased in areas where the ground was rich in leaf litter. Similarly, adult activity was observed only when relative humidity was over 65%. Temporally, we found that peaks in abundance followed large rainfall events. Nevertheless, this mosquito was under significant density dependence regulation. Our results suggest that
Ar. subalbatus
population peaks following large rainfall events could reflect the recruitment of individuals that were dormant as dry eggs. We did not find a clear signal of temperature on abundance changes of this mosquito, but only on its phenology. Since ground cover seemed more critical than temperature to its spatial distribution, we propose that this mosquito might have some degree of autonomy to changes in temperature.
Aedes albopictus (Skuse) has expanded its distribution worldwide during the past decades. Despite attempts to explain and predict its geographic occurrence, analyses of the distribution of Ae. albopictus in the context of broad climatic regions (biomes) has not been performed. We analyzed climate conditions at its distribution sites in the range before the worldwide invasions (from the easternmost Hawaii through westernmost Madagascar) by using thermal and aridity-humidity indices descriptive of major biomes. A significant advantage of this approach is that it uses simple indices clearly related to the population dynamics of Ae. albopictus. Although Ae. albopictus has been regarded as a forest species preferring humid climate, in areas with significant human habitation, the distribution sites extended from the perhumid, rain forest zone to the semiarid, steppe zone. This pattern was common from the tropics through the temperate zone. Across the distribution range, there was no seasonal discordance between temperature and precipitation; at sites where winter prevents Ae. albopictus reproduction (monthly means <10°C), precipitation was concentrated in warm months (>10°C) under the Asian summer monsoon. Absence of the species in northern and eastern coastal Australia and eastern coastal Africa was not attributable solely to climate conditions. However, Asia west of the summer monsoon range was climatically unsuitable because of low precipitation throughout the year or in warm months favorable to reproduction (concentration of precipitation in winter). We hypothesized that Ae. albopictus originated in continental Asia under the monsoon climate with distinct dry seasons and hot, wet summer, enabling rapid population growth.
© The Authors 2015. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
By simulating 640,000 time-series either 30 or 300 observations long, I evaluated the precision and power of significance tests for four measures of nonmetric time-series: Colwell's C and M and Goodman and Kruskal's @l"R@?"C and @t"R"@?"C. Significance tests for all four measures are powerful but do not fit published @g^2 and t values. An Appendix gives critical levels for the test statistics of all four measures for tables from 2 x 2 to 5 x 5 and for time-series with lengths 30 and 300. To detect the significant periodicities in a time-series with C and M, one should calculate the measures for many different time classes (contingency will peak when the number of time classes matches a natural periodicity), and sample at least twice as frequently as the period of the highest frequency fluctuation that one wants to detect (more frequently if asymmetric fluctuations are suspected). Colwell's measures were not as sensitive as Fourier transforms in detecting significant periodicities in metric test data, but their overall performance on metric data was good enough to justify their use on nominal and ordinal data. A method is given for estimating from pilot data the sampling effort required to detect a significant fluctuation.
Okinawa is the largest, most urbanized, and densely populated island in the Ryukyus Archipelago, where mosquito species diversity has been thoroughly studied. However, the south-central Okinawa mosquito fauna has been relatively poorly studied. Here, we present results from a mosquito faunal survey in urban environments of Nishihara city, south-central Okinawa. Mosquitoes were sampled biweekly, from April 2007 to March 2008, at 3 different environments: a forest preserve, an animal farm, and a water reservoir. We employed 4 mosquito collection methods: 1) oviposition traps; 2) light traps; 3) sweep nets; and 4) larval surveys of tree holes, leaf axils, and artificial water containers. We collected a total of 568 adults and 10,270 larvae belonging to 6 genera and 13 species, including 6 species of medical importance: Aedes albopictus, Armigeres subalbatus, Anopheles Hyrcanus group, Culex bitaeniorhynchus, Cx. quinquefasciatus, and Cx. tritaeniorhynchus. Mosquito species composition was similar to data from previous studies in Okinawa Island. The flattening of the species accumulation curve suggests that our diversity sampling was exhaustive with light and oviposition traps, as well as the coincidence between the species richness we found in the field and estimates from the Chao2 index, a theoretical estimator of species richness based on species abundance. This study highlights the importance of combining several sampling techniques to properly characterize regional mosquito fauna and to monitor changes in the presence of mosquito species.
Larvae of the mosquito Uranotaenia novobscura ryukyuana Tanaka et al., have been reported in tree-holes, bamboo stumps, and artificial water containers. So far, no study has addressed the role that density dependence and weather fluctuations could have played in the abundance of this nonvector mosquito. A year-long study was conducted on the population dynamics of this mosquito using oviposition traps in Okinawa, Japan. Time series analysis and the Ricker population model were used to analyze the association between mosquito density and population growth and fluctuations in relative humidity, temperature, and rainfall. Our results suggest that Ur. novobscura ryukyuana has stable denso-dependent dynamics, which are autonomous from weather fluctuations. Our results were opposite to patterns observed in other subtropical mosquito species, whose population dynamics might be partially driven by weather fluctuations, thus highlighting the diversity of responses that mosquitoes can have to changing environments.
Pathogen transmission by mosquitos is known to be highly sensitive to mosquito bionomic parameters. Mosquito mark-release-recapture (MMRR) experiments are a standard method for estimating such parameters including dispersal, population size and density, survival, blood feeding frequency and blood meal host preferences.
We assembled a comprehensive database describing adult female MMRR experiments. Bibliographic searches were used to build a digital library of MMRR studies and selected data describing the reported outcomes were extracted.
The resulting database contained 774 unique adult female MMRR experiments involving 58 vector mosquito species from the three main genera of importance to human health: Aedes, Anopheles and Culex. Crude examination of these data revealed patterns associated with geography as well as mosquito genus, consistent with bionomics varying by species-specific life history and ecological context. Recapture success varied considerably and was significantly different amongst genera, with 8, 4 and 1% of adult females recaptured for Aedes, Anopheles and Culex species, respectively. A large proportion of experiments (59%) investigated dispersal and survival and many allowed disaggregation of the release and recapture data. Geographic coverage was limited to just 143 localities around the world.
This MMRR database is a substantial contribution to the compilation of global data that can be used to better inform basic research and public health interventions, to identify and fill knowledge gaps and to enrich theory and evidence-based ecological and epidemiological studies of mosquito vectors, pathogen transmission and disease prevention. The database revealed limited geographic coverage and a relative scarcity of information for vector species of substantial public health relevance. It represents, however, a wealth of entomological information not previously compiled and of particular interest for mosquito-borne pathogen transmission models.
The impact of climate change on the distribution of Aedes albopictus (Skuse) was analyzed in northern Japan, where chronological distribution records are incomplete. We analyzed local climate data using linear regression of the thermal suitability index (TSI) for the mosquito and mean annual temperature as functions of time. In northern Japan, thermal conditions since the early 20th century have become increasingly suitable for Ae. albopictus, more as a result of decreasing coldness in the overwintering season than increasing warmth in the reproductive season. Based on recent discovery records of Ae. albopictus in the northern border range, we determined thermal criteria for estimating when its persistent establishment became thermally possible. Retrospective analyses indicated that those criteria were reached in most coastal lowlands of northern Honshu before the accelerated temperature increase after the mid-1980s and the first records of this species after 1990; at some sites, temperature criteria were reached during or before the early 20th century. Expansion of the thermally suitable range after 1990 was supported only for inland areas and the northernmost Pacific coast. The estimated expansion rate was ≈26 km per decade. Our analyses also demonstrated the importance of local climate heterogeneity (apart from north‐south or altitudinal temperature gradients) in determining the expansion pattern.
Landsat 8, a NASA and USGS collaboration, acquires global moderate-resolution measurements of the Earth's terrestrial and polar regions in the visible, near-infrared, short wave, and thermal infrared. Landsat 8 extends the remarkable 40 year Landsat record and has enhanced capabilities including new spectral bands in the blue and cirrus cloud-detection portion of the spectrum, two thermal bands, improved sensor signal-to-noise performance and associated improvements in radiometric resolution, and an improved duty cycle that allows collection of a significantly greater number of images per day. This paper introduces the current (2012–2017) Landsat Science Team's efforts to establish an initial understanding of Landsat 8 capabilities and the steps ahead in support of priorities identified by the team. Preliminary evaluation of Landsat 8 capabilities and identification of new science and applications opportunities are described with respect to calibration and radiometric characterization; surface reflectance; surface albedo; surface temperature, evapotranspiration and drought; agriculture; land cover, condition, disturbance and change; fresh and coastal water; and snow and ice. Insights into the development of derived ‘higher-level’ Landsat products are provided in recognition of the growing need for consistently processed, moderate spatial resolution, large area, long-term terrestrial data records for resource management and for climate and global change studies. The paper concludes with future prospects, emphasizing the opportunities for land imaging constellations by combining Landsat data with data collected from other international sensing systems, and consideration of successor Landsat mission requirements.
The Asian bush or rock pool mosquito Aedes japonicus japonicus is one of the most expansive culicid species of the world. Being native to East Asia, this species was detected out of its original distribution range for the first time in the early 1990s in New Zealand where it could not establish, though. In 1998, established populations were reported from the eastern US, most likely as a result of introductions several years earlier. After a massive spread the mosquito is now widely distributed in eastern North America including Canada and two US states on the western coast. In the year 2000, it was demonstrated for the first time in Europe, continental France, but could be eliminated. A population that had appeared in Belgium in 2002 was not controlled until 2012 as it did not propagate. In 2008, immature developmental stages were discovered in a large area in northern Switzerland and bordering parts of Germany. Subsequent studies in Germany showed a wide distribution and several populations of the mosquito in various federal states. Also in 2011, the species was found in southeastern Austria (Styria) and neighbouring Slovenia. In 2013, a population was detected in the Central Netherlands, specimens were collected in southern Alsace, France, and the complete northeastern part of Slovenia was found colonized, with specimens also present across borders in adjacent Croatia. Apparently, at the end of 2013 a total of six populations occurred in Europe although it is not clear whether all of them are completely isolated. Similarly, it is not known whether these populations go back to the same number of introductions. While entry ports and long-distance continental migration routes are also obscure, it is likely that the international used tyre trade is the most important mode of intercontinental transportation of the mosquito. Aedes j. japonicus does not only display an aggressive biting behaviour but is suspected to be a vector of various disease agents and to displace indigenous culicid species. Therefore, Aedes j. japonicus might both cause public health problems in the future and have a significant impact on the biodiversity of the invaded territories.
The invasive Asian tiger mosquito Aedes albopictus has recently been observed in southern Germany for the first time to reproduce and even overwinter north of the Alps. After the accidental capture of adult specimens in Jena, German federal state of Thuringia, in mid-2015, regular inspections brought forth developmental stages until autumn 2015, indicating local reproduction. Surveillance activities implemented in 2016 showed larvae already in early May, suggesting overwintering, and throughout the season until late October, although population densities remained low. Further sporadic specimens found in 2017 argue for establishment. Jena is located in Central Germany, north of all known distribution areas of Ae. albopictus, with the area of the municipality affected by the tiger mosquito characterised by a relatively mild climate. To check the suitability of the local climate for Ae. albopictus, winter temperatures, measured in a cemetery of Jena where larvae had regularly been found in 2015 and 2016, were analysed and compared with two sites of establishment in southern Germany. The conditions were similar at all three locations, suggesting that the Jena population might also be able to survive in the long term. While the municipality authorities have been informed and education of the Jena citizens to avoid producing potential breeding places has started, insecticidal control has not yet been implemented.
Spatial synchrony plays an important role in dictating the dynamics of spatial and stage-structured populations. Here we argue that, unlike Moran effect where spatial synchrony is driven by exogenous factors, spatial correlation in intrinsic/local scale processes, can affect the level of spatial synchrony among distinct sub-populations, and therefore the persistence of the entire population. To explore this mechanism, we modelled the consequences of spatial heterogeneity in aquatic habitat quality, and that of temporal variation in local extinction probability, on the persistence of stage-structured mosquito populations. As a model system, we used two widely distributed mosquito species, Aedes albopictus and Culex pipiens, both key vectors of a range of infectious diseases. Spatial heterogeneity in aquatic habitat quality led to increased population persistence, and this pattern was more pronounced at intermediate dispersal rates, and in the long-dispersing species (C. pipiens). The highest regional persistence was obtained at high dispersal rates. This is probably because dispersal, in our model, did not carry any additional costs. Population persistence of both species was negatively correlated with increased temporal variation in local extinction probability. These differences were stronger in the short-dispersing species (A. albopictus), especially at intermediate dispersal rates. The dispersal of A. albopictus adults in each time step was limited to the nearest habitat patches, weakening the positive effect of spatial heterogeneity in aquatic habitat quality on population persistence. In contrary, C. pipiens adults could disperse into more remote sub-populations, resulting in much higher recolonization rates. Hence, the negative effect of temporal variation in local extinction probability on patch occupancy disappeared at intermediate dispersal rates. We suggest that effectively controlling these two mosquito species requires making few spatially synchronized control efforts (i.e., generating high temporal variation in local extinction probability), rather than many asynchronized local control efforts. Finally, our model can be easily fitted to other organisms characterized by complex life cycles, and it can be also used to examine alternative scenarios, including the effect of spatial configuration of local habitat patches and dispersal kernel shape on population persistence. This article is protected by copyright. All rights reserved.
This chapter focuses on the impacts of changing climate on arthropod vectors of disease, their relationship with the pathogens they transmit, and the implications of these phenomena for disease transmission,ceteris paribus, that is, assuming everything else stays the same. It introduces a case study that illustrates some of the complexities present when untangling the potential role of climate change on the distribution of disease vectors. Useful concepts to study impacts of climate change on insect vectors of disease are illustrated with this study on changes in the distribution of two major globally invasive vectors: Aedes albopictus and Aedes japonicus, facing the emergence of Aedes flavopictus, formerly a rare species along an altitudinal gradient in Nagasaki, Japan. The basic pattern that has been observed regarding the impact of temperature on pathogens developing inside vectors of disease is that the extrinsic incubation period (EIP).
A guide to using S environments to perform statistical analyses providing both an introduction to the use of S and a course in modern statistical methods. The emphasis is on presenting practical problems and full analyses of real data sets.
In order to know the mosquito fauna and biology in the forest area in the northern part of Okinawajima, Ryukyu Islands, Japan, a mosquito survey was conducted monthly for 6 years from 1976 to 1981. Collections were made mainly at a seaside cemetery (area H), foot of a mountain (area YS and YE) and a jungle forest (area AD). Adult mosquitoes were collected by daytime human-bait catches and larvae were also collected by a dipper and pipet from their natural habitats and at artificial containers such as wooden box, earthen jar, tin can and glass vial which had been placed beforehand. In total, 31 species of 11 genera were found in the present survey. Among them Ae. japonicus was a newly recorded species in Okinawajima. Larvae of Ur. nivipleura were also newly recorded in Japan. Toxorhynchites sp. is very similar to Tx. towadensis, belonging to the Tx. manicatus group. This species was very rare but its larvae were collected from wooden boxes placed in the jungle forest. The overwintering of the species was made in the larval stage. The larvae of Cx. ryukyensis, Ae. albopictus and Ur. n. ryukyuana were commonly found in area H. Most of the females collected in this area were Ae. albopictus (95%) and a few Ar. subalbatus (4%) was also included. At the base of the mountain, the larvae of Ae. albopictus, Ae. f. downsi, Ae. riversi, Ae. a. okinawanus and Or. anopheloides were predominant. In the YS area, teh predominant females were Ae. albopictus (60%) and Ar. subalbatus (38%). In the YE area, Ae. albopictus (40%), An. saperoi (31%) and Ae. riversi (15%) were predominant and the rest were Ar. subalbatus, Ae. a. okinawanus and Ae. f. downsi in decreasing order. In the jungle forest area (AD), the predominant species breeding in the artificial containers were the same as those in areas YS and YE except Ae. albopictus which was never collected in this area. The most common species that came to bite in the area was An. saperoi (62%) and its immature stages were commonly found in streams. Considerable numbers of Ae. a. okinawanus (25%) and Ae. riversi (8%) also came to bite in this area. Engorged females and/or larvae in all instars and pupae of Ae. albopictus, Ae. riversi, An. saperoi, Ae. a. okinawanus, Ar. subalbatus, Cx. ryukyensis and Ur. n. ryukyuana were collected even in winter. Apparently blood feeding, oviposition and adult emergence of these species continued in the winter season.
MODIStsp is a new R package allowing automating the creation of raster time series derived from MODIS Land Products. It allows performing several preprocessing steps (e.g. download, mosaicing, reprojection and resize) on MODIS products on a selected time period and area. All processing parameters can be set with a user-friendly GUI, allowing users to select which specific layers of the original MODIS HDF files have to be processed and which Quality Indicators have to be extracted from the aggregated MODIS Quality Assurance layers. Moreover, the tool allows on-the-fly computation of time series of Spectral Indexes (either standard or custom-specified by the user through the GUI) from surface reflectance bands. Outputs are saved as single-band rasters corresponding to each available acquisition date and output layer. Virtual files allowing easy access to the entire time series as a single file using common image processing/GIS software or R scripts can be also created. Non-interactive execution within an R script and stand-alone execution outside an R environment exploiting a previously created Options File are also possible, the latter allowing scheduling execution of MODIStsp to automatically update a time series when a new image is available. The proposed software constitutes a very useful tool for the Remote Sensing community, since it allows performing all the main preprocessing steps required for the creation of time series of MODIS data within a common framework, and without requiring any particular programming skills by its users.
Females of 15 species of Japanese mosquitoes were studied to determine if they were susceptible to mouse-adapted dengue-2 virus (New Guinea C strain) by oral administration of the virus mixed with rabbit blood and sucrose. The following species were tested : Aedes (Stegomyia) albopictus, Ae. (Stg.) flavopictus, Ae. (Stg.) riversi, Ae. (Ochlerotatus) dorsalis, Ae. (Aedimorphus) vexans nipponii, Ae. (Finlaya) japonicus, Ae. (Fin.) togoi, Armigeres (Armigeres) subalbatus, Anopheles (Anopheles) sinensis, Culex (Culex) orientalis, Cx. (Cux.) pipiens molestus, Cx. (Cux.) pipiens pallens, Cx. (Cux.) pipiens quinquefasciatus, Cx. (Cux.) tritaeniorhynchus and Tripteroides (Tripteroides) bambusa. Several hundred mosquitoes were used for each species. They were kept at 30℃ after the infection, and were stored at -80℃ after the incubation of various time length from 0 to 30 days. The detection and titration of the virus were made by the intracranial injection of a suspension pool of 10 mosquitoes in suckling mice (ddY strain). The virus was detected at varying titers from all the mosquito species immediately after the infection, but was detected after 20 days of infection only from the four species, i. e., Ae. (Stg.) albopictus, Ae. (Stg.) flavopictus, Ae. (Stg.) riversi and Ae. (Och.) dorsalis, ranging from "trace" to≧(10)^<4.6> LD_<50> per pool. In more detailed studies with the positive mosquito species, the virus was found to multiply after an eclipse period of 7 to 10 days and to reach a peak titer after 20 to 30 days.
Developed by Luca Congedo, the Semi-Automatic Classification Plugin (SCP) is a free open source plugin for QGIS that allows for the semi-automatic classification (also known as supervised classification) of remote sensing images. It provides several tools for the download of free images, the preprocessing, the postprocessing, and the raster calculation. The overall objective of SCP is to provide a set of intertwined tools for raster processing in order to make an automatic workflow and ease the land cover classification, which could be performed also by people whose main field is not remote sensing. The first version of the SCP was written by Luca Congedo in 2012 for the ACC Dar Project in order to create a tool for the classification of land cover in an affordable and automatic fashion (read this working paper). Following versions of SCP were developed as personal commitment to the remote sensing field and open source software. SCP version 6 (codename: Greenbelt) is developed in the frame of Luca Congedo’s PhD in Landscape and Environment at Sapienza University of Rome.
This user manual provides information about the Plugin Installation of SPC and the The Interface of SCP, with detailed information about all the functions. In addition, the Brief Introduction to Remote Sensing illustrates the basic concepts and definitions which are required for using the SCP. Basic Tutorials are available for learning the main functions of SCP and Thematic Tutorials illustrate specific tools.
Pathogen transmission by mosquitos is known to be highly sensitive to mosquito bionomic parameters. Mosquito mark-release-recapture (MMRR) experiments are a standard method for estimating such parameters including dispersal, population size and density, survival, blood feeding frequency and blood meal host preferences.
We assembled a comprehensive database describing adult female MMRR experiments. Bibliographic searches were used to build a digital library of MMRR studies and selected data describing the reported outcomes were extracted.
The resulting database contained 774 unique adult female MMRR experiments involving 58 vector mosquito species from the three main genera of importance to human health: Aedes, Anopheles and Culex. Crude examination of these data revealed patterns associated with geography as well as mosquito genus, consistent with bionomics varying by species-specific life history and ecological context. Recapture success varied considerably and was significantly different amongst genera, with 8, 4 and 1% of adult females recaptured for Aedes, Anopheles and Culex species, respectively. A large proportion of experiments (59%) investigated dispersal and survival and many allowed disaggregation of the release and recapture data. Geographic coverage was limited to just 143 localities around the world.
This MMRR database is a substantial contribution to the compilation of global data that can be used to better inform basic research and public health interventions, to identify and fill knowledge gaps and to enrich theory and evidence-based ecological and epidemiological studies of mosquito vectors, pathogen transmission and disease prevention. The database revealed limited geographic coverage and a relative scarcity of information for vector species of substantial public health relevance. It represents, however, a wealth of entomological information not previously compiled and of particular interest for mosquito-borne pathogen transmission models.
The surface reflectance, i.e., satellite derived top of atmosphere (TOA) reflectance corrected for the temporally, spatially and spectrally varying scattering and absorbing effects of atmospheric gases and aerosols, is needed to monitor the land surface reliably. For this reason, the surface reflectance, and not TOA reflectance, is used to generate the greater majority of global land products, for example, from the Moderate Resolution Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) sensors. Even if atmospheric effects are minimized by sensor design, atmospheric effects are still challenging to correct. In particular, the strong impact of aerosols in the visible and near infrared spectral range can be difficult to correct, because they can be highly discrete in space and time (e.g., smoke plumes) and because of the complex scattering and absorbing properties of aerosols that vary spectrally and with aerosol size, shape, chemistry and density.
When predicting a numeric outcome, some measure of accuracy is typically used to evaluate the model’s effectiveness. However, there are different ways to measure accuracy, each with its own nuance. In Section 5.1 we define common measures for evaluating quantitative performance. We also discuss the concept of variance-bias trade-off (Section 5.2), and the implication of this principle for predictive modeling. In Section 5.3, we demonstrate how measures of predictive performance can be generated in R.
Vegetation indices are important remotely sensed metrics for ecosystem monitoring and land surface process assessment, among which Normalized Difference Vegetation Index (NDVI) has been most widely used. The newly launched Landsat 8 Operational Land Imager (OLI) sensor, together with its predecessor Landsat 7 Enhanced Thematic Mapper Plus (ETM +), provides continuous earth observations with an 8-day interval. The design improvements of the new sensor, including narrower near-infrared waveband, higher signal-to-noise ratio (SNR), and greater radiometric sensitivity highlight the need for investigating the land surface observation properties, especially its consistency with data from its predecessors and other satellite sensors. This study aims to evaluate the characteristics of Landsat 8 OLI-derived NDVI against Landsat 7 ETM + by cross-comparison and by comparing with Moderate Resolution Imaging Spectroradiometer (MODIS) and Geostationary Ocean Color Imager (GOCI)-derived NDVIs as well as in-situ NDVI measurements. Simulations of Top of Atmosphere (TOA) reflectance and surface reflectance of broadleaf trees and water were conducted for Landsat 8 OLI, Landsat 7 ETM +, and MODIS in order to evaluate the impact of band pass difference on NDVI calculation. Four consecutive pairs of Landsat 8 OLI and Landsat 7 ETM + data over China and Korea were examined, and NDVIs derived from TOA reflectance and surface reflectance by three atmospheric correction methods were evaluated. Both simulations and comparisons showed that NDVIs derived from atmospherically-corrected surface reflectance had good consistency, while the simulation showed that the agreement varied with atmospheric characteristics. The four pairs of Landsat 8 OLI and Landsat 7 ETM + NDVI had a mean bias error within ± 0.05, and R2 from 0.84 to 0.98. Vegetated land cover types were found to have better NDVI agreement than non-vegetated land cover types. Especially, Landsat 8 OLI consistently generated lower NDVI values in water area than Landsat 7 ETM +, which resulted from higher aerosol optical thickness in atmosphere. Landsat 8 OLI-derived NDVI showed better agreement with MODIS and GOCI NDVI than Landsat 7 ETM +, mainly on vegetated surfaces. Both Landsat 8 OLI and Landsat 7 ETM + surface reflectance-derived NDVI agreed well with in-situ light emitting diode (LED) NDVI measurements at a homogeneous deciduous forest site. Landsat 8 OLI was also found to produce higher spatial variability of NDVIs than Landsat 7 ETM + at vegetated and urban areas, but lower variability on water area. The overall good agreement between Landsat 8 OLI NDVI and Landsat 7 ETM +, MODIS and GOCI NDVIs as well as in-situ measurements ensures that it is reliable to integrate the new sensor observations with those from the multiple satellite sensors, given that the same atmospheric correction methods are applied. Furthermore, the greater NDVI contrast between vegetated areas and water areas, and the higher spatial variability of Landsat 8 OLI NDVI indicated that the new sensor has better capability in land surface process monitoring, such as land cover mapping, spatiotemporal dynamics of vegetation growth, and drought assessment.
Mosquitoes were collected weekly from May 2003 to December 2013 at a pair of sites within the premises of the National Institute of Infectious Diseases, Tokyo, Japan. The mosquito trap was equipped with 1 kg dry ice and battery-operated suction mechanism. A total of 10,546 adults belonging to 7 species in 3 genera were collected in this study. Aedes albopictus and Cx. pipiens gr. were the dominant mosquitoes, composing 99.7% of the total mosquitoes collected. Six and 12 adults of Cx. tritaeniorhynchus were collected in early spring and in late summer to autumn, respectively. More Cx. pipiens gr. were collected at the high trap site near a tree canopy rather than the low trap site near the ground every year, whereas only 1 to 15% of Ae. albopictus were collected at the high trap site, indicating a difference in searching behavior between the two species. The female density of Cx. pipiens gr. was high (>10/trap/day) during early June to early August, and a high Cx. pipiens gr.-related risk is expected in this period. Density of female Ae. albopictus was high (>10/trap/day) during the 28th to 41st week, suggesting a high risk of transmission of Ae. albopictus-borne pathogens from mid-July to mid-October in Tokyo.
The utility of cytochrome c oxidase subunit I (COI) DNA barcoding for the identification of 37 mosquito species belonging to the genera Anopheles (6 spp.), Aedes (14 spp.) and Culex (17 spp.) including subspecies from nine islands of the Ryukyu Archipelago, Japan was examined. A 658 bp fragment of the COI gene was sequenced from 228 specimens. Nucleotide sequence divergences were calculated using the Kimura-two parameter (K2P) distance model and a neighbor-joining (NJ) phylogenetic tree analysis was performed to provide a graphic display of the patterns in divergence among species. The mean intraspecific variations of 35 species including the medically important vector species showed a less than 2% range with 0–1.5% divergences, but higher divergences of more than 2% were detected in Ae. aureostriatus okinawanus Bohart (2.2%) and Cx. hayashii ryukyuanus Tanaka et al. (3.3%). They showed differences in divergence between specimens from different islands. All 37 species were discriminated as distinct clusters in the NJ tree. The results in this study prove the utility of DNA barcoding for identification of mosquitoes from the Ryukyu Archipelago, Japan.
Two Japanese mosquitoes of Culex infantulus and Tripteroides bambusa have been colonized and sustained for 15 and 10 generations respectively. The adults are maintained in screened cages (60 • ~60 • ~30 cm for C. infantulus and 30 • ~30 • ~20 cm for T. bambusa) placed in the laboratory with daily photoperiod of 16 hours normal white light and 30 minutes each of dawn and dusk lighting conditions. Temperatures range from 24 to 26 C and relative humidity is 70 to 80 percent. Blood meals are provided by placing a restrained turtle for infantulus and an anesthetized mouse for T. bambusa.
There is growing recognition that linking patterns to their underlying processes in interconnected and dynamic ecological systems requires data sampled at multiple spatial and temporal scales.
However, spatially explicit and temporally resolved data sets can be difficult to analyze using classical statistical methods because the data are typically autocorrelated and thus violate the assumption of independence.
Here, we describe the synchrony package for the R programming environment, which provides modern parametric and nonparametric methods for (i) quantifying temporal and spatial patterns of auto‐ and cross‐correlated variability in univariate, bivariate, and multivariate data sets, and (ii) assessing their statistical significance via Monte Carlo randomizations.
We illustrate how the methods included in the package can be used to investigate the causes of spatial and temporal variability in ecological systems through a series of examples, and discuss the assumptions and caveats of each statistical procedure in order to provide a practical guide for their application in the real world.