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Cría de mosquitos Culicidae y evaluación de insecticidas de uso en salud pública.
Abstract
Esta guía surge de la necesidad de contar con material biológico óptimo para fines de investigación básica o aplicada, en el campo o laboratorio, lo que justifica la cría y mantenimiento de colonias de insectos transmisores de enfermedades en condiciones de insectario. El Centro Regional de Investigación en Salud Pública cuenta con 30 años de experiencia en investigación sobre la cría de los vectores de dengue y malaria en el sur del país, así como con colaboraciones realizadas en México y en el extranjero con el objetivo de lograr homogeneidad en la producción en masa y desarrollo sincronizado de este material. En esta obra se presentan los lineamientos para la implementación y operación de insectarios de una manera práctica, económica y sencilla, de utilidad para grupos operativos nacionales e internacionales que busquen producir mosquitos de importancia médica. Complementariamente, se dedica una sección a la descripción de procedimientos normalizados para la evaluación de insecticidas de uso en salud pública, una intervención central en el control de las poblaciones de mosquitos vectores, ante la ausencia de medicamentos o vacunas eficaces contra padecimientos como malaria, fiebre amarilla, dengue, chikungunya y Zika.
... The larvae were reared according to standardized techniques. 15,16 Pupae were sexed using a glass plate separator (John W. Hock Co., Gainesville, FL, USA). All the experiments were carried out in the Centro Regional de Investigación en Salud Pública (CRISP) insectary in Tapachula, Chiapas, Mexico, from January to December 2018. ...
... From that moment, they remain in copulation, taking a random sample of 30 females from each treatment at times of 1, 24, and 48 hr for spermathecae analysis. 16 ...
... After 48 hr of coexistence, a random sample of 30 females were taken to extract the three spermathecae, recording the number of positives to sperm. 16 They were provided with cotton soaked in a 10% sucrose solution in all the treatments. ...
Objective. To development of a methodology for the chilling, handling, transport, and release of male Aedes aegypti mosquitoes, reared in insectary conditions to release in the field with unmanned vehicles to compete sexually with wild males in the field. Materials and methods. A population of Ae. aegypti from different areas in Tapachula, Chiapas, was used. Laboratory tests were conducted: Effect of temperature and cooling time on the knockdown, recovery of males, and copulatory success. Results. The chilling temperature of 3 ± 1ºC for 30 min, was used as a knockdown temperature before handling, packing, transportation, and aerial release.
The males subjected to the entire process, including the semi-field aerial release test, showed normal sexual behavior activity, obtaining 100% of females inseminated. Conclusion. These results present the feasibility of applying a new
control methodology using unmanned aerial vehicle (UAV) as support for the sterile insect release technique (SIT), use of Wolbachia or both, in male Ae. aegypti, for the design of strategies to control their populations.
Background:
The susceptibility of Anopheles albimanus and An. pseudopunctipennis to local Plasmodium vivax has been associated in southern Mexico with two ookinete surface proteins (Pvs25/28) polymorphism. Perhaps parasite population selection (i.e. adaptation to local vectors) contributes to this phenomenon. It is also possible that certain molecular interactions exist between P. vivax and each mosquito species independently of geographical origin. This study aimed to explore the susceptibility of An. albimanus and An. pseudopunctipennis (collected from different geographical sites) to P. vivax cspVk/Pvs25-130 haplotypes from southern Mexico.
Results:
Of the 120 P. vivax-infected blood samples used to simultaneously feed An. albimanus and An. pseudopunctipennis mosquitoes originating from various geographical sites, 80 produced at least one infected mosquito species. Three parasite haplotypes were identified in infected blood: Vk210/Pvs25-A (12.5%), Vk210/Pvs25-B (20%) and Vk247/Pvs25-B (67.5%). Two parameters (the proportion of infected mosquitoes and number of oocysts/mosquito) showed a similar pattern for each mosquito species (independently of geographical origin). For An. albimanus mosquitoes (from the Pacific coast, Mexican gulf and Lacandon Forest lowlands), these two parameters were higher in specimens infected with P. vivax Vk210/Pvs25-A versus Vk210/Pvs25-B or Vk247/Pvs25-B (P < 0.001). For An. pseudopunctipennis mosquitoes (from the Pacific coast, northeast Mexico and east Guatemala foothills), the same two parameters were higher in specimens infected with Vk247/Pvs25-B or Vk210/Pvs25-B versus Vk210/Pvs25-A (P < 0.001). Higher infection rates were caused by Vk247/Pvs25-B than Vk210/Pvs25-B parasites in An. pseudopunctipennis (P = 0.011) and An. albimanus (P = 0.001). The greatest parasitaemia, gametocytaemia and microgamete formation was observed in Vk247/Pvs25-B infected blood, and each of these parameters correlated with each other and with the number of oocysts in An. pseudopunctipennis from the sympatric colony.
Conclusions:
Plasmodium vivax Vk247/Pvs25-B infections were the most prevalent, likely due to the higher parasitaemia produced in the susceptible vector (especially An. pseudopunctipennis). The analysis of mosquito-parasite interactions indicate that An. pseudopunctipennis and An. albimanus each have a unique pattern of transmitting genetic variants of P. vivax, and this is not dependent on geographical origin. The present findings highlight the importance of parasite genotyping to understand transmission dynamics and vectorial participation.
Anopheles darlingi is the main malaria vector in the Amazon region and is among the most efficient malaria vectors worldwide. However, due to the lack of a well-established laboratory colony, key control-relevant aspects of the bionomics, behaviour, genetics, and vector-parasite relationships of An. darlingi remain unknown. Here, biological parameters that had been successful in initiating other Anopheles colonies were optimized and improved for An. darlingi, with the aim of establish a free-mating, stable, and highly productive laboratory colony.
Wild An. darlingi adult females were field collected from Zungarococha, Loreto Department, Peru (03°49'32.40″S, 73°21'00.08″W), and taken to the NAMRU-6 Insectary in Iquitos where F1 offspring were produced and reared. Natural copulation was successfully induced in F1 adults under a thermo-period of 30 ± 1 °C during the day and 25 ± 1 °C at night, and with a 30-min LED light stimulation period at dusk. Oviposition success was enhanced using egg-laying containers with a dark-coloured surface. Larval feeding regimes were standardized for optimal larval development. Optimized copulation induction methods were used to facilitate mating in An. darlingi until the F10 generation. No copulation induction assistance was needed in subsequent generations.
In 19 generations, the An. darlingi colony produced a total of 763,775 eggs; 441,124 larvae; 248,041 pupae; and 231,591 adults. A mean of 0.56 sexual encounters/female/cage (n = 36 cages) was recorded across the first ten generations (F1-F10). A mean insemination rate of 54.7 % (n = 5,907 females) ranging from 43.6 % (F2) to 66.6 % (F10) was recorded across nine generations (F2-F10). Free-mating was casually observed in the F8 generation, and subsequently confirmed in the F9 and F10 generations; comparable insemination rates and egg laying between stimulated (51.6 %, 12.9 eggs / female), and non-stimulated (52.3 %, 11.2 eggs / female) females were recorded. The time from egg to adult development ranged from 10 to 20 days. Moreover, the colony was relocated to a new laboratory within Iquitos in the F14 generation without any noted changes in its productivity. To date (March 2015), the An. darlingi colony has been successfully reared to the F26 generation.
This constitutes the first report of a free-mating, highly productive, and long-standing An. darlingi laboratory colony established through natural copulation induction, which will support critical malaria research. This rearing methodology may be a transferable, cost-effective alternative to labour-intensive forced mating practices widely used in maintaining other Anopheles colonies.
In this study, we designed a new tent trap; the BioDiVector (BDV) tent trap, consisting of two rectangular tents that use human bait without endangering the technical personnel. The daily activity pattern of Aedes aegypti and Aedes albopictus in intra, peri, and extradomiciliary sites was studied in an endemic area of dengue in southern Mexico by using the BDV tent trap. Totals of 3,128 individuals of Ae. aegypti and 833 Ae. albopictus were captured. More Ae. aegypti males than females were caught, while the opposite was true with Ae. albopictus. The activity of both mosquito species was affected by the interaction between the collection site and time of day. In general, more individuals of both mosquito species were captured at the extradomicillary sites than at the peri and intradomicillary sites. Mosquitoes showed two peaks of activity, one in the morning and the other in the afternoon, but in general this only occurred at the extradomicillary sites, whereas no peak of activity was observed at the intra and peridomicillary sites. Overall, Ae. aegypti had a higher indirect biting rate than Ae. albopictus. Finally, due to its efficiency, simplicity, and low cost, we suggest the use of this innovative tool for entomological surveillance, bionomics and vector incrimination studies in geographical areas where dengue and other arboviruses are present.
Anopheles darlingi is one of the most important malaria vectors in the Americas. In this era of new tools and strategies for malaria and vector control it is essential to have knowledge on the ecology and behavior of vectors in order to evaluate appropriateness and impact of control measures. This paper aims to provide information on the importance, ecology and behavior of An. darlingi. It reviews publications that addressed ecological and behavioral aspects that are important to understand the role and importance of An. darlingi in the transmission of malaria throughout its area of distribution. The results show that Anopheles darlingi is especially important for malaria transmission in the Amazon region. Although numerous studies exist, many aspects determining the vectorial capacity of An. darlingi, i.e. its relation to seasons and environmental conditions, its gonotrophic cycle and longevity, and its feeding behavior and biting preferences, are still unknown. The vector shows a high degree of variability in behavioral traits. This makes it difficult to predict the impact of ongoing changes in the environment on the mosquito populations. Recent studies indicate a good ability of An. darlingi to adapt to environments modified by human development. This allows the vector to establish populations in areas where it previously did not exist or had been controlled to date. The behavioral variability of the vector, its adaptability, and our limited knowledge of these impede the establishment of effective control strategies. Increasing our knowledge of An. darlingi is necessary.
In Thailand, water-storage jars, barrels, drums, pails, and tanks constitute vast developmental sites for Aedes aegypti in urban, semiurban, and rural areas. Earthen water jars, cement jars, and concrete tanks constitute the greatest proportion of artificial containers where Ae. aegypti breed. This species is a major vector of the causal agents of dengue and dengue hemorrhagic fever, and vector control by larviciding is one of the main approaches to disease control. At present, temephos sand granules (SG) (1%) are used in large-scale community-based larviciding programs. Because of the use of this larvicide over the past 30 years, the likelihood exists that Ae. aegypti already has become resistant to this larvicide. To develop more options for control and make them available for use, we evaluated VectoBac tablets (Bacillus thuringiensis var. israelensis [Bti] 5%) and a new formulation of zeolite granules (ZG) of temephos (1%) and compared these formulations for efficacy with temephos SG (1%) in water-storage jars. In these tests, we used 48 identical glazed earthen water-storage jars (200-liter capacity) and developed quantitative sampling procedures for larvae, pupae, and pupal skins. Pupal skins were the easiest to count and this technique was used for the 1st time for assessing emergence of adults in water-storage containers. Three water regimens were used: full jars, half-full jars, and full jars emptied half way and refilled weekly. The 3 formulations with 3 regimens of water were assessed over a period of 6 months. VectoBac tablets at the dosage of 1 tablet or 0.37 g per 50 liters of water provided excellent control for about 112 days in full water jars. In the other 2 water regimens, VectoBac gave excellent control for 90 days. The 2 temephos formulations at the operational rate of 5 g per 50 liters of water were equal in efficacy, yielding almost 100% control for more than 6 months. Unlike temephos SG, the temephos ZG had no objectionable odor. Both the temephos ZG and Bti tablets increased clarity of the water, a feature desired by the users. Lack of odor and depression of turbidity are important attributes of Bti tablets and temephos ZG.
Preceding chapters have mainly described various methods for sampling the different developmental stages and age groups of Mosquito populations. This chapter is concerned with analysing the numerical changes that occur in population size during the life-cycle of mosquitoes, identifying the causes of mortalities, and determining the age structure and survival rates of adult populations. A comprehension of the growth and regulation of Mosquito populations is essential for understanding their population dynamics. Darwin (1859) wrote ‘There is no exception to the rule that every organic being naturally increases at so high a rate, that if not destroyed, the earth would soon be covered by the progeny of a single pair’. It follows that with animals such as mosquitoes which have high growth potential that at some time during the period from egg to ovipositing female there must be large mortalities. The measurement of these mortalities has interested ecologists and statisticians alike, and many of the techniques used are founded on mathematical probabilities.
A mechanical device, modified from a previous design, is described for separating the developmental stages, sexes, and species of mosquitoes.
Village-scale trials were carried out in southern Mexico to compare the efficacy of indoor-spraying of the pyrethroid insecticide lambda-cyhalothrin applied either as low-volume (LV) aqueous emulsion or as wettable-powder (WP) aqueous suspension for residual control of the principal coastal malaria vector Anopheles albimanus. Three indoor spray rounds were conducted at 3-month intervals using back-pack mist-blowers to apply lambda-cyhalothrin 12.5 mg a.i./m2 by LV, whereas the WP was applied by conventional compression sprayer at a mean rate of 26.5 mg a.i./m2.
Both treatments caused mosquito mortality indoors and outdoors (collected inside house curtains) as a result of contact with treated surfaces before and after feeding, but had no significant impact on overall population density of An. albimanus resting indoors or assessed by human bait collections. Contact bioassays showed that WP and LV treatments with lambda-cyhalothrin were effective for 12–20 weeks (>75% mortality) without causing excito-repellency.
Compared to the WP treatment (8 houses/man/day), LV treatment (25 houses/man/day) was more than 3 times quicker per house, potentially saving 68% of labour costs. This is offset, however, by the much lower unit price of a compression sprayer (e.g. Hudson ‘X-pert’ at US120) than a mist-blower (e.g. ‘Super Jolly’ at US350), and higher running costs for LV applications. It was calculated, therefore, that LV becomes more economical than WP after 18.8 treatments/100 houses/10 men at equivalent rates of application, or after 7.6 spray rounds with half-rate LV applications.
Two colonies of Anopheles pseudopunctipennis, Tapachula and Abasolo strains, were established under laboratory conditions with a thermoperiod (29 degrees C during the day; 24 degrees C during the night) and artificial dusk. To stimulate mating, a light beam from a flashlight was shone on the cage shortly after lights off. This procedure was repeated for the first 6 mosquito generations (parental to F6) and thereafter light stimulation was unnecessary for mating. The Tapachula colony has been maintained for 24 generations in 24 months, with insemination rates in females > 80% since the F3, and a monthly production of 30,000 pupae since the F7. Using the same procedure, the Abasolo colony from northeastern Mexico has been maintained for 13 generations in 14 months, with insemination rates of 26-52%.