Bionomía del mosquito Aedes (Stegomyia) aegypti Ll.) En iglesias y cementerio de la ciudad de Mérida, Yucatán, México, y la identificación de arbovirus.

RESUMEN: Aedes aegypti es el vector principal de los virus dengue (VDEN), Zika (VZIK) y chikungunya (VCHIK). Aunque su bionomía es bien documentada para casas, su comportamiento es poco conocido en sitios públicos. En el presente estudio, la bionomía de Ae. aegypti fue descrito en iglesias y cementerio de la ciudad de Mérida, Yucatán. Los sitios de estudio fueron visitados cuatro veces por mes entre septiembre de 2015 y octubre de 2016. Los mosquitos adultos, fueron capturados con aspiradores de mochila. Las larvas y pupas fueron colectadas con la ayuda de pipetas de plástico. La duración del ciclo gonotrófico fue estimado con el análisis de correlación cruzada, basado en la paridad diaria de Ae. aegypti durante 25 días. La preferencia alimenticia del mosquito fue determinada con el gen del citocromo b de humanos y mamíferos. Los arbovirus fueron identificados con RT-PCR mediante la amplificación de regiones específicas de los genes de VDEN, VZIK y VCHIK. Durante todo el periodo de estudio, en las iglesias se colectaron 6,051 larvas y 315 pupas. Mientras que, en el cementerio se colectaron 8,052 larvas y 575 pupas. En cuanto los mosquitos adultos de Ae. aegypti, se colectaron en iglesias 1,380 hembras. De las cuales, 1,178 en la estación de lluvias y 202 en la de seca; la mayoría estaban alimentadas (615). En el cementerio se obtuvieron 1,648 hembras con 1,471 en periodo de lluvias y solo 177 en el de secas; la mayoría estaban sin alimentar (823). En ambos sitios de estudio, la duración del ciclo gonotrófico fue de cuatro días en temporada de lluvia y tres días en la temporada de secas. El 76% (223/292) de hembras de Ae. aegypti con alimentación reciente fueron analizadas y todas fueron identificadas con sangre de humano. En las iglesias fueron identificados dos pools de Ae. aegypti infectadas con el virus dengue (DEN-1 y 2). En el cementerio, un pool de Ae. aegypti fue infectado con dengue (DEN-1) y otro con el virus Zika. Los resultados sugieren que las iglesias y el cementerio de la ciudad de Mérida, Yucatán representan riesgo potencial en la transmisión de arbovirus. ABSTRACT: Aedes aegypti is the main vector of the dengue, Zika and chikungunya viruses. Although its bionomy is well documented in houses, their behavior is little known in public places. In the present study, the bionomy of Ae. aegypti was described in churches and cemetery of the Mérida city, Yucatán. Field work was undertaken from September 2015 to October 2016 and sampling was conducted four times per month. Resting mosquitoes were collected by using backpack-mounted aspirators. Nets, turkey basters, or pipettes were used to collect immatures from water-holding containers. Daily changes in the parous–nulliparous ratio was recorded for 25 days, and the gonotrophic cycle length was estimated by a time series analysis and the source of bloodmeal of Ae. aegypti. The host preference of Ae. aegypti was determined with the human and mammalian cytochrome b gene. Aedes aegypti females were processed for VDEN, VZIK and VCHIK identification by RT-PCR. For the entire study, 6,051 larvae and 315 pupae were collected in churches. In cemetery, 8,052 larvae and 575 pupae were collected. Of the Ae. aegypti adults, 1,380 females were collected in churches. Of which, 1,178 in the rainy season and 202 in the dry season; most were fed (615). In cemetery, 1,648 females were collected, with 1,471 in the rainy season and 177 in the dry season; most were unfed (823). In both study sites, the duration of the gonotrophic cycle was four and three days in rainy and dry season, respectively. For source of bloodmeal, we processed 76% (223/292) of Ae. aegypti females with freshly blood and all females tested were identified with human blood. In churches, two positive pools to dengue virus (DENV-1 and DENV-2) were identified. In cemetery, one pool was positive a DEN-1 and another to Zika virus. The results suggest that churches and cemetery represents potential risk of arbovirus transmission in Merida city

Complete Genome Sequence of Houston Virus, a Newly Discovered Mosquito-Specific Virus Isolated from Culex quinquefasciatus in Mexico

ABSTRACT We fully sequenced the genome of Houston virus, a recently discovered mosquito-associated virus belonging to the newly established family Mesoniviridae. The isolate was recovered from Culex quinquefasciatus in southern Mexico, which shows that the geographic range of Houston virus is not restricted to the United States in North America

Study of Aedes aegypti population with emphasis on the gonotrophic cycle length and identification of arboviruses: implications for vector management in cemeteries

Aedes aegypti is the vector of the arboviruses causing dengue, chikungunya and zika infections in Mexico. However, its presence in public places has not been fully evaluated. In a cemetery from Merida, Yucatan, Mexico, the productivity of Ae. aegypti, the gonotrophic cycle, and the presence of Ae. aegypti females infected with arboviruses were evaluated. Immature and adult mosquitoes were inspected every two months between April 2016 to June 2017. For the gonotrophic cycle length, the daily pattern of total and parous female ratio was registered and was analyzed using time series analysis. Ae. aegypti females were sorted into pools and assayed for flavivirus RNA by RT-PCR and Sanger sequencing. Aedes aegypti immatures represented 82.86% (8,627/10,411) of the collection. In total, 1,648 Ae. aegypti females were sorted into 166 pools. Two pools were positive; one for dengue virus (DENV-1) and the other for zika virus (ZIKV). The phylogenetic analysis revealed that the DENV-1 is more closely related to isolates from Brazil. While ZIKV is more closely related to the Asian lineage, which were isolates from Guatemala and Mexico. We report some evidence of vertical transmission of DENV-1 in nulliparous females of Ae. aegypti. The gonotrophic cycle was four and three days in the rainy and dry season, respectively. The cemetery of Merida is an important focus of Ae. aegypti proliferation, and these environments may play a role in arboviruses transmission; probably limiting the efficacy of attempts to suppress the presence of mosquitoes in domestic environments

Determinación de la acetilcolinesterasa insensible asociada a la resistencia a insecticidas en Culex quinquefasciatus, Say,1823 (Diptera: Culicidae) colectadoss en Yucatán, México

Acetylcholinesterase is an enzyme whose main function is to terminate the transmission of nerve impulses in the cholinergic synapse in insects through the hydrolysis of acetylcholine. However, frequent applications of insecticides can select for individuals with an alteration in the enzyme and functional changes that result in an insensitivity to insecticides. In Mexico, the current strategy to combat insect vectors such as Culex quinquefasciatus is based mainly on the use of synthetic insecticides. The use of these chemicals in health and agricultural practices may also contribute to mosquito insensitivity to several groups of insecticides. Therefore, it is considered necessary to determine if there is any physiological mechanism associated with resistance. For this reason, the objective of this research was to identify if there is insensitivity of acetylcholinesterase to insecticides in Cx. quinquefasciatus populations, collected in urban and rural areas of the State of Yucatán, Mexico. Enzymatic tests were carried out with slight modifications to the established protocols. Areas were identified with mosquito populations showing acetylcholinesterase insensitivity to propoxur, a carbamate insecticide. We consider it important to determine the environmental factors that affect the behavior and response of mosquitoes following exposure to insecticides, and this knowledge could inform the design of efficient strategies in vector control programs. La acetilcolinesterasa es una enzima, cuya principal función es finalizar la transmisión de los impulsos nerviosos en la sinapsis colinérgica en los insectos mediante la hidrólisis de la acetilcolina. Sin embargo, el uso frecuente de los insecticidas sintéticos, probablemente originen una alteración en la enzima y cambios funcionales conduciendo a la insensibilidad a los insecticidas neurotóxicos. En México la estrategia actual para el combate de insectos vectores como Culex quinquefasciatus, se basa principalmente en el uso de estos compuestos. El uso de estos productos químicos en áreas de la salud y prácticas agrícolas probablemente contribuye a la insensibilidad a diferentes grupos de insecticidas. Por lo tanto, se considera necesario determinar si existe algún mecanismo fisiológico asociado a la resistencia. Por tal motivo, el objetivo de esta investigación fue identificar si existe insensibilidad de la acetilcolinesterasa a insecticidas en poblaciones de Cx. quinquefasciatus, colectados en áreas urbanas y rurales en Yucatán. Se realizaron pruebas enzimáticas con ligeras modificaciones en los protocolos establecidos y se identificaron áreas con poblaciones de mosquitos con acetilcolinesterasa insensible a propoxur, que es un carbamato ampliamente utilizado en México. Con nuestro trabajo consideramos importante identificar los factores ambientales que afectan el comportamiento y respuesta de los mosquitos a los insecticidas, lo cual será de gran utilidad para el diseño eficiente de estrategias en los programas de control de vectores

Prevalence of gastrointestinal parasites in domestic dogs in Tabasco, southeastern Mexico

Abstract The overall goal of this study was to estimate the prevalence of gastrointestinal (GI) parasites in dogs in the city of Villahermosa in Tabasco, Mexico. The study population consisted of 302 owned dogs that had limited access to public areas. A fecal sample was collected from each animal and examined for GI parasites by conventional macroscopic analysis and centrifugal flotation. Fecal samples from 80 (26.5%) dogs contained GI parasites. Of these, 58 (19.2%) were positive for helminths and 22 (7.3%) were positive for protozoan parasites. At least seven parasitic species were identified. The most common parasite was Ancylostoma caninum which was detected in 48 (15.9%) dogs. Other parasites detected on multiple occasions were Cystoisospora spp. (n = 19), Toxocara canis (n = 7) and Giardia spp. (n = 3). Three additional parasites, Dipylidium caninum, Trichuris vulpis and Uncinaria spp., were each detected in a single dog. No mixed parasitic infections were identified. In summary, we report a moderately high prevalence of GI parasites in owned dogs in Villahermosa, Tabasco. Several parasitic species identified in this study are recognized zoonotic pathogens which illustrates the important need to routinely monitor and treat dogs that live in close proximity to humans for parasitic infections

Entomological and virological surveillance for dengue virus in churches in Merida, Mexico

ABSTRACT This study was designed to assess whether churches in endemic dengue districts in Merida, Mexico provide suitable breeding habitats for mosquitoes and are potential sites for dengue virus (DENV) transmission. Churches were inspected for immature and adult mosquitoes once every week from November 2015 to October 2016. A total of 10,997 immatures of five species were collected. The most abundant species were Aedes aegypti (6,051) and Culex quinquefasciatus (3,018). The most common source of immature Ae. aegypti were buckets followed by disposable containers. Adult collections yielded 21,226 mosquitoes of nine species. The most common species were Cx. quinquefasciatus (15,215) and Ae. aegypti (3,902). Aedes aegypti were found all year long. Female Ae. aegypti (1,380) were sorted into pools (166) and assayed for flavivirus RNA by RT-PCR and Sanger sequencing. Two pools were positive for DENV (DENV-1 and 2). In conclusion, we demonstrated that some churches in Merida are infested with mosquitoes all year long and they potentially serve as sites for DENV transmission and should therefore be considered for inclusion in mosquito and arboviruses control and surveillance efforts