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map of Soth America (A), showing the location of Bolivia, depart- ment and city of Cochabamba (B) and the two studied areas (C) of Velle Hermoso and Temporal, in the South and North zones, respectively.
Source publication
Chagas disease is a major public health problem in Bolivia. In the city of Cochabamba, 58% of the population lives in peripheral urban districts ("popular zones") where the infection prevalence is extremely high. From 1995 to 1999, we studied the demographics of Chagas infections in children from five to 13 years old (n = 2218) from the South zone...
Contexts in source publication
Context 1
... area -Two districts in the periphery of CO (Fig. 1A, B), the SZ (Valle Hermoso) and NZ (Temporal) (Fig. 1) were chosen for the study based on geographic, social, and economic differences. The general characteristics of the families living in the peripheral districts or "popular zones" are as follows (Bailey-Lazcano & Trewhella-Fernandez 1998): (a) all are migrants, and most are second or ...
Context 2
... area -Two districts in the periphery of CO (Fig. 1A, B), the SZ (Valle Hermoso) and NZ (Temporal) (Fig. 1) were chosen for the study based on geographic, social, and economic differences. The general characteristics of the families living in the peripheral districts or "popular zones" are as follows (Bailey-Lazcano & Trewhella-Fernandez 1998): (a) all are migrants, and most are second or third generation (e.g., in the SZ, 55% were born in ...
Context 3
... rates are reported in individuals less than 10 years old. In the village of Tabacal, 40% of infected chil- dren fall within this age group (Pless et al. 1992 ), and in the village of Mizque, a study reported 11.8% and 44.1% prevalence rates for children aged from one to five and six to 10 years old, respectively (Brenière et al. 2002). The city of Cochabamba (CO) is situated in Central Bolivia and has a population of about 752,613 (INE 2001). In previously published work, Laserna (1995) observed that 55% of the population in CO originates from other cities, and 70% of the population had emigrated from ru- ral areas. In fact, immigrants accounted for 30% of the total population (Ledo & Zelada 1989, INE 2001, Blanes 2006), and this is most likely secondary to political, eco- nomic, and social causes (Bailey-Lazcano & Trewhella- Fernandez 1998). Individuals immigrated to the urban zone in pursuit of a better quality of life and improved conditions for their families (Calderon & Toranzos 1984). Bolivia is currently undergoing the process of ur- banization, and the rural population has decreased from 58.5% in 1976 to approximately 42% in 1992 (INE 2001). Peripheral districts or “popular zones” are home to 58% of the city’s population (Bailey-Lazcano & Trewhella- Fernandez 1998). The majority of people living in these districts (40%) originates from rural villages and may act to transport triatomine vectors from rural to urban areas. Despite the fact that Chagas disease is classically considered to be a rural illness, it may also become an urban disease. Arata et al. (1994) have reported a sero- logical infection prevalence of 17.5% in a female popula- tion composed of 2,850 individuals. The prevalence was determined to vary by age: 4.6% infection prevalence in infants younger than one year old, 7.2% in children aged one to four years old, 16% in children aged five to nine years old and 22.9% in individuals 15 to 44 years of age. The San Simon University created an Inter-Institutional Committee for the Control of Chagas disease in peri- urban districts of CO and demonstrate a prevalence of 39.6% and 62.2% (H Gonzáles, unpublished observa- tions) in two particular areas: Nova Santa Veracruz and Villa San Andrés, respectively. Recent work by Cortez et al. (2006) clearly describes the conditions of the wild bug infestation in the region of CO. In the present paper, we evaluated the seropositivity of children from two geographically [North (NZ) and South (SZ) zones], socially, and economically distinct urban regions of urban CO with the aims of answering the following questions: is there any difference between seropositivity for Chagas disease in regions with differ- ent socio-economic profiles? What is the clinical status of the infected population in regards to cardiac pathol- ogy? What are the risk factors for Chagas infection in these populations? Study area - Two districts in the periphery of CO (Fig. 1A, B), the SZ (Valle Hermoso) and NZ (Temporal) (Fig. 1) were chosen for the study based on geographic, social, and economic differences. The general characteristics of the families living in the peripheral districts or “popular zones” are as follows (Bailey-Lazcano & Trewhella-Fer- nandez 1998): (a) all are migrants, and most are second or third generation (e.g., in the SZ, 55% were born in the CO, 10.5% were from rural villages in the same district, and the remainder were from other districts); (b) basic public services are scarce and living conditions are poor; (c) most of the families are in the lower socioeconomic class and live in precarious houses with inconsistent ac- cess to health and education; (d) the families have sev- eral children; (e) the mother is the head of the house- hold, generally working as an informal salesperson on the streets while their husbands are working in CO or other cities; (f) the educational background of parents is minimal; and (g) there is a high frequency of malnour- ished children. As for the history of the two areas, both of them have the following in common: (a) the fact that the districts were previously farm land that was slowly transformed into an urban area; and (b) a significant im- migrant population (from Oruro and Potosi in the SZ and from country villages of CO in the NZ). The districts chosen for the study differ in the following: (a) the social conditions, which are superior in the NZ as compared to the SZ as indicated by better general living conditions and higher educational levels; (b) the environmental con- ditions, with a drier climate in the SZ than in the NZ; and (c) agricultural resources, which are present in the NZ and absent in the SZ (Sostres & Delgado 1993). Individuals and blood samples - In this study, 2,218 children were examined with ages ranging from five to 13 years old (Fig. 2A). Of the data collected, 899 indi- viduals were living in the SZ and 1,319 in the NZ of CO. Identification of the study population was conducted during 1995 to 1996 (SZ) and 1996 to 1999 (NZ). The subjects were recruited during regular school attendance in both districts. To introduce the study, we presented several seminars (Fig. 2B) for the students, parents (Fig. 2C), and teachers as well as for the directors of the school board in order to obtain an effective collaboration. The aim of these seminars was to inform the individuals about the importance of Chagas disease in Bolivia, as well as to share with them the objectives of the research project. Prior to inclusion in this study, formal written in- formed consent was obtained from all parents or guardians for blood collection, clinical examination, and treatment of the involved children. Blood donation was voluntary, and treatment was offered to all individuals with posi- tive serum reactivity to T. cruzi independent of their par- ticipation in the study. For the serological studies, 2 ml of blood was collected from each child, separated by centrifugation, and the serum obtained was used for se- rological assays in the same day. Clinical examination and electrocardiogram (EKG) were performed by two of the authors (R U-F, V B) for all individuals (Fig. 2D). Each physician completed a distinct set of forms, which included identification of the individual, epidemiologi- cal and clinical information, the EKG reading, and sero- logical data. Both of the authors read the EKG profiles in order to confirm the results. Serum samples of dogs living in the SZ were collected and analyzed by indirect hemagglutination assay (IHA) assays. This study was approved by the Fiocruz Ethics Committee in Research, according to the Brazilian resolution 196/96. nosorbent assay (ELISA) - IHA was performed using a commercially available diagnostic kit (Polychaco, Buenos Aires, Argentina). The serum was diluted 1/16, 1/32, and 1/64, and positive and negative controls were employed for all test plates. This assay was also used to analyze the dog serum samples. ELISA was performed using a commercial available kit (Chagastest, Buenos Aires, Argentina) and as with the IHA analysis, posi- tive and negative controls provided in the kit were used with all samples. Statistical analysis - All information obtained in this study was transcribed into a data base and statistical analy- ses performed using SAS (Statistical Analysis Software®) or Statistica for Windows (StatSoft). Logistic regression analyses were performed by one of the authors (HLG). under study - Table I demonstrates that the SZ cohort accounted for 40.6% (902) and the NZ cohort for 59.4% (1,319) of the study population. The mean number of persons per family was similar (6 to 7 persons) in both zones. However, large families composed of 20 or more individuals were reported in both the SZ and NZ. The number of children attending school was also similar between the districts, with a mean of four individuals per family. The majority of the children in both areas demonstrated a basic knowledge of triatomine vectors (93.8% in ...
Citations
... The process of peri-urbanization of triatomine species, with invasion or colonization of peripheral neighborhoods in small towns and large cities, is a current problem (Medrano-Mercado et al., 2008;Carbajal-de-la-Fuente et al., 2022). Infected T. infestans were also detected in a peri-urban neighborhood of Pampa del Indio when the rural area was under sustained surveillance (Provecho et al., 2014). ...
The interruption of domestic vector-borne transmission of Trypanosoma cruzi in the Americas remains one of the main goals of the World Health Organization 2021-2030 road map for neglected tropical diseases. We implemented a longitudinal intervention program over 2015-2022 to suppress (peri)domestic Triatoma infestans in the municipality of Avia Terai, Chaco Province, Argentina and found that house infestation (3851 houses inspected) and triatomine abundance decreased over the first 2 years post-intervention (YPI), and remained stable thereafter associated to moderate pyrethroid resistant foci. Here we assessed selected components of transmission risk after interventions across the rural-to-urban gradient. We used multistage random sampling to select a municipality-wide sample of T. infestans. We examined 356 insects collected in 87 houses for T. cruzi infection using kDNA-PCR and identified their bloodmeal sources using an indirect ELISA. The overall prevalence of T. cruzi infection post-intervention was 1.7% (95% CI 0.7-3.6). Few houses (5.7%) (95% CI 2.5-12.8) harbored infected triatomines across the gradient. Infected triatomines were found in 5 peri-urban or rural dwellings over 1-4 years post-intervention. No infected insect was found in the urban area. The human blood index decreased from 66.2 at baseline to 42.8 at 1YPI and then increased to 92.9 at 4-5 YPI in the few infested domiciles detected. The percentage of houses with human-fed bugs displayed a similar temporal trend. Our results indicate marginal risks of domestic vector-borne transmission across the district after implementation of the intervention program. Ensuring sustainable vector surveillance coupled with human etiological diagnosis and treatment in hiperendemic areas like the Gran Chaco region, is urgently needed. 252 words.
... The city of Cochabamba in Bolivia is a rare example of comparable urban scale with similar levels of triatomine infection in some districts [50]. Cochabamba also suffers from high human seropositivity for T. cruzi [70]. Rates of human infection in Caracas, however, are currently unknown. ...
Chagas disease is a significant public health risk in rural and semi-rural areas of Venezuela. Triatomine infection by the aetiological agent Trypanosoma cruzi is also observed in the Metropolitan District of Caracas (MDC), where foodborne T. cruzi outbreaks occasionally occur but active vector-to-human transmission (infection during triatomine bloodmeal) is considered absent. Citizen science-based domiciliary triatomine collection carried out between 2007 and 2013 in the MDC has advanced understanding of urban T. cruzi prevalence patterns and represents an important public awareness-building tool. The present study reports on the extension of this triatomine collection program from 2014 to 2019 and uses mitochondrial metabarcoding to assess feeding behavior in a subset of specimens. The combined, thirteen-year dataset (n = 4872) shows a high rate of T. cruzi infection (75.2%) and a predominance of Panstrongylus geniculatus (99.01%) among triatomines collected in domiciliary areas by MDC inhabitants. Collection also involved nymphal stages of P. geniculatus in 18 of 32 MDC parishes. Other collected species included Triatoma nigromaculata, Triatoma maculata, Rhodnius prolixus, and Panstrongylus rufotuberculatus. Liquid intestinal content indicative of bloodmeal was observed in 53.4% of analyzed specimens. Dissection pools representing 108 such visually blooded P. geniculatus specimens predominantly tested positive for human cytochrome b DNA (22 of 24 pools). Additional bloodmeal sources detected via metabarcoding analysis included key sylvatic T. cruzi reservoirs (opossum and armadillo), rodents, and various other synanthropic and domesticated animals. Results suggest a porous sylvatic-domiciliary transmission interface and ongoing adaptation of P. geniculatus to the urban ecotope. Although P. geniculatus defecation traits greatly limit the possibility of active T. cruzi transmission for any individual biting event, the cumulation of this low risk across a vast metropolitan population warrants further investigation. Efforts to prevent triatomine contact with human food sources also clearly require greater attention to protect Venezuela's capital from Chagas disease.
... Regarding the transmission of Chagas, several studies have documented the infestation of urban dwellings by vectors of epidemiological importance, such as Triatoma infestans in the cities of Arequipa (Peru) [23], San Juan (Argentina) [14] and Cochabamba (Bolivia) [24], and Panstrongylus geniculatus in Caracas (Venezuela) [25,26]. However, the occurrence of triatomines in urban areas ("urban triatomism") and, consequently, its relevance in the vectorial transmission of T. cruzi, possibly related to some specific regions of the American continent, have not yet been evaluated exhaustively and objectively on a continental scale. ...
Background
Chagas is a complex and multidimensional socio-environmental health phenomenon, in which different components converge and interact. Historically, this disease was associated with insect vectors found in the rural environment. However, in the Americas, we are currently facing a new paradigm, in which different scenarios allow maintaining the vectorial transmission of the parasite through triatomine populations that either occasionally enter the dwellings or colonize urban environments.
Methodology/Principal findings
Records of scientific reports available in the PubMed and LILACS search engines were retrieved, using three criteria according to the main triatomine genera of epidemiological importance and to the general scientific production on Chagas disease in urban contexts. Results showed that records on the occurrence of vectors in urban dwellings began to increase in the last three decades. Results also showed that the main species of triatomines collected inside dwellings (18 in total) belong mainly to the genera Triatoma and Panstrongylus , with most species (16/18, 88.8%) infected with the parasite, and that infestation of triatomine species occurs in all types of cities (small, medium and large, including megalopolises), from Argentina to the USA.
Conclusions/Significance
Urban Chagas represents a new challenge that adds a different dimension to the problem of Chagas disease due to the particular characteristics of the lifestyle in urban agglomerates. The new scenario will require adaptations of the programs of control of vector to this shift from rural to urban settlements.
... However, 20%-40% of chronically infected patients will develop serious cardiac and/or gastrointestinal complications. [5,6] While the pathogenesis of Chagas cardiomyopathy is not entirely understood, it is believed that parasite-induced neuronal damage, microvascular dysfunction, and autoimmunity contribute to tissue fibrosis, remodeling, and dysautonomia, leading to heart failure, arrhythmias, and thromboembolic events. [3,4] A similar pathophysiological mechanism may be responsible for the gastrointestinal complications associated with CD. ...
... [7] It has been almost 80 years since the first Chagas case was reported in Bolivia, and as of now, Bolivia has one of the highest prevalence of Chagas in Latin America. [5,6] CD is particularly prevalent in poor and rural areas -studies in 2007 and 2011 found a seroprevalence in adults as high as 80% in endemic regions in Bolivia. [8,9] Even though the prevalence of T. cruzi infection has decreased in the past decades, CD remains a significant public health problem. ...
... The feeding characteristics of T. dimidiata (i.e., opportunistic and host generalist status), and assisted movement of bugs by rural human migration to Mérida (Chi-Méndez, 2016) could help sylvatic insects to move into the urban landscape, thereby increasing genetic diversity and reducing the genetic structuration (e.g., "Urban facilitation models, " Miles et al., 2019). Since infestation and transmission of CD in urban settings has increased elsewhere (Vallvé et al., 1996;Levy et al., 2006;Medrano-Mercado et al., 2008;Carvalho et al., 2014;Parente et al., 2017;Alvedro et al., 2021), there is a potential signal for urban evolution in triatomines, due to the presence of a suitable niche where susceptible hosts are abundant and not intermittent (Bradley and Altizer, 2007). What factors could be driving such niche search? ...
Environmental change (i.e., urbanization) impacts species in contrasting ways, with some species experiencing benefits given their way of life (i.e., blood-sucking insects). How these species respond to such change is not well understood and for species involved in human diseases, this “how” question is particularly important. Most Triatominae bug species inhabit tropical and subtropical forests where their vertebrate hosts’ temporal abundance depends on climate seasonality. However, in human encroached landscapes, triatomines can benefit from resource stability which may lead to adaptive phenotypic change to track novel hosts. We tested for an association between different landscapes and morpho-functional traits linked to sensory, motion, and feeding functions in Triatoma dimidiata and compared fecundity (i.e., number of eggs) in each landscape as a proxy of fitness. Using geometric and traditional morphometric tools, we predicted a morphological simplification in bugs inhabiting urbanized areas. While wing morphology or proboscis were not influenced by landscape class, the opposite occurred for thorax morphology and number of sensilla. Wing and thorax morphology did not covary under modified landscape scenarios, yet we detected a morpho-functional convergence for thorax size and antennal phenotype in both sexes, with a simplification trend, from nature to urban settings. Given no fecundity differences across landscapes, there is no potential reproductive costs. Moreover, the convergence of thorax size and antennal phenotype suggests differences in flight/locomotion performance and host/environment perception, as a possible adaptive response to relaxed selective pressures of the bug’s native habitat. These results imply that T. dimidiata could be adapting to urbanized areas.
... The steady rural-to-urban migration recorded during the twentieth century and projected for future decades, combined with increasing travel and transportation of goods from rural to peri-urban or urban areas, provides multiple routes of entry of triatomine bugs into habitats wrongly assumed not to be at risk of infestation. Consequently, several species of triatomines (including T. infestans, T. dimidiata, Triatoma pallidipennis, and Mepraia spinolai) colonized peri-urban and urban habitats and even invaded the top stories of city buildings through flight dispersal (Vallvé et al. 1996;Albarracin-Veizaga et al. 1999;Cattan et al. 2002;Ramsey et al. 2005;Levy et al. 2006;Guzman-Tapia et al. 2007;Medrano-Mercado et al. 2008;Lima et al. 2012;Gaspe et al. 2020). Peri-urban areas, defined as "the areas where the urban core intermingles with adjacent 'non-urban' systems" (MacGregor-Fors 2011), provide a transition between urban and rural areas. ...
Triatomine species largely differ in their degrees of adaptation to thrive in domestic habitats, blood-feed on humans, and transmit Trypanosoma cruzi. Pathogen transmission dynamics are shaped by ecological, biological, and social factors. Here we link housing quality and host availability to the host-feeding patterns of domestic triatomines and examine how their blood-feeding performance affects temperature-dependent vital rates and bug population dynamics. The stability/instability habitat divide connects with the large/small triatomine population size dichotomy and on whether bug population dynamics are density-dependent or density-independent and dominated by stochasticity. Seasonal variations in temperature acting on triatomine blood-feeding activity and human-vector contact rates determined the spring peak of symptomatic acute cases of Chagas disease in northern Argentina across four decades. The presence of domestic animals (dogs, cats, and chickens) and commensal rodents increases domestic infestation, vector infection, and parasite transmission across multiple settings and triatomine species. Both ecological and social factors contribute to human infection risk through social vulnerability, mobility patterns, and housing instability. Understanding the interactions among eco-bio-social factors may lead to the design and implementation of improved, sustainable disease control or elimination strategies.
... Fuente: Moncayo & Silveira, 2009 La transmisión en Bolivia es principalmente vectorial, con Triatoma infestans como el principal transmisor, de importancia en salud pública por estar domiciliado en los 6 departamentos endémicos: La Paz, Cochabamba, Santa Cruz, Chuquisaca, Potosí y Tarija con diferentes zonas geográficas entre los 300 a 3.000 metros de altitud (Noireau 1999, WHO 2002. A pesar de que la transmisión vectorial en Bolivia se caracteriza clásicamente por ser propia de áreas rurales, ahora se conocen focos de transmisión vectorial urbana en la ciudad de Cochabamba donde se identificaron además altas seroprevalencias de la infección en niños y adolescentes (Medrano-Mercado et al. 2008). ...
... Urban infestations and vector-borne transmission of T. cruzi have increasingly been reported in endemic regions throughout Central and South America [9][10][11][12][13][14][15][16]. In Cochabamba (Bolivia) and Arequipa (Peru), peri-urban infestations with Triatoma infestans, the main vector in the region, have been linked to the immigration of farmers from rural areas [13,17]. ...
Background
Peri-urban and urban settings have recently gained more prominence in studies on vector-borne transmission of Trypanosoma cruzi due to sustained rural-to-urban migrations and reports of urban infestations with triatomines. Prompted by the finding of Triatoma infestans across the rural-to-urban gradient in Avia Terai, an endemic municipality of the Argentine Chaco, we assessed selected components of domestic transmission risk in order to determine its variation across the gradient.
Methods
A baseline vector survey was conducted between October 2015 and March 2016, following which we used multistage random sampling to select a representative sample of T. infestans at the municipal level. We assessed T. cruzi infection and blood-feeding sources of 561 insects collected from 109 houses using kinetoplast DNA-PCR assays and direct enzyme-linked immunosorbent assays, respectively. We stratified triatomines according to their collection site (domestic or peridomestic), and we further categorized peridomestic sites in ecotopes of low- or high-risk for T. cruzi infection.
Results
The overall adjusted prevalence of T. cruzi -infected T. infestans was 1.8% (95% confidence interval [CI] 1.3–2.3) and did not differ between peri-urban (1.7%) and rural (2.2%) environments. No infection was detected in bugs captured in the urban setting; rather, infected triatomines were mainly collected in rural and peri-urban domiciles, occurring in 8% of T. infestans -infested houses. The main blood-feeding sources of domestic and peridomestic triatomines across the gradient were humans and chickens, respectively. The proportion of triatomines that had fed on humans did not differ between peri-urban (62.5%) and rural (65.7%) domiciles, peaking in the few domestic triatomines collected in urban houses and decreasing significantly with an increasing proportion of chicken- and dog- or cat-fed bugs. The relative odds ratio (OR) of having a T. cruzi infection was nearly threefold higher in bugs having a blood meal on humans (OR 3.15), dogs (OR 2.80) or cats (OR: 4.02) in a Firth-penalized multiple logistic model.
Conclusions
Trypanosoma cruzi transmission was likely occurring both in peri-urban and rural houses of Avia Terai. Widespread infestation in a third of urban blocks combined with high levels of human–triatomine contact in the few infested domiciles implies a threat to urban inhabitants. Vector control strategies and surveillance originally conceived for rural areas should be tailored to peri-urban and urban settings in order to achieve sustainable interruption of domestic transmission in the Chaco region.
... Currently, most infected people are found in (peri)urban areas and non vectorial (congenital, oral) routes of transmission have taken more relative importance. Yet, vector-borne transmission still represents a significant public health concern in rural parts of Bolivia, Paraguay and Argentina, and vector adaptation to urban settings puts large numbers of people at risk (Medrano-Mercado et al. 2008). Today, it is estimated that 50,000 new cases occur annually with more than 100 million being at risk of infection (PAHO 2006). ...
This volume of the Neglected Tropical Diseases (NTD) series covers the most prevalent NTDs in Europe and Central Asia. This book discusses in detail the pathology, diagnostics and control approaches of the most important neglected pathogens occurring in these geographical regions. Each chapter focuses on one specific disease or group of related diseases, and provides the reader with in-depth insights into the topic. This volume addresses researchers in Microbiology and Biomedicine as well as clinicians and public health officials working in affected regions.
... [9,[14][15][16][17][18][19]). Triatoma infestans, the main vector of T. cruzi in the Gran Chaco region, has increasingly being reported to colonise houses in peri-urban and urban areas of Argentina, Bolivia and Peru, and established local transmission cycles [9,10,[20][21][22][23]. Whether urban infestation is a (re)emerging threat or a long-standing, overlooked issue is unclear and has implications for a mechanistic understanding of system dynamics and policy development. ...
Background:
The occurrence of the major vectors of Chagas disease has historically been linked to poor rural housing, but urban or peri-urban infestations are increasingly being reported. We evaluated a simple risk index to detect houses infested with Triatoma infestans and tested whether house infestation and vector abundance increased across the urban-to-rural gradient in Avia Terai, an endemic municipality of the Argentine Chaco; whether the association between infestation and selected ecological determinants varied across the gradient; and whether urban and peri-urban infestations were associated with population settlement history.
Methods:
We conducted a screening survey of house infestation in 2296 urban, peri-urban and rural dwellings to identify high-risk houses based on a simple index, and then searched for triatomines in all high-risk houses and in a systematic sample of low-risk houses.
Results:
The risk index had maximum sensitivity and negative predictive value, and low specificity. The combined number of infested houses in peri-urban and urban areas equalled that in rural areas. House infestation prevalence was 4.5%, 22.7% and 42.4% across the gradient, and paralleled the increasing trend in the frequency of domestic animals and peridomestic structures. Multiple logistic regression analysis showed that house infestation was positively and significantly associated with the availability of poultry and bug refuges in walls, and was negatively associated with domestic insecticide use. Several pieces of evidence, including absence of spatial aggregation of house infestation, support that T. infestans has been a long-established occupant of urban, peri-urban and rural settings in Avia Terai.
Conclusions:
An integrated vector management strategy targeting chicken coops and good husbandry practices may provide more cost-effective returns to insecticide-based vector elimination efforts.
