Bionomía del mosquito Culex quinquefasciatus (SAY, 1823)) y su relación con el virus del oeste del nilo (VON) en la ciudad de Mérida, Yucatán, México

El virus del Oeste del Nilo (VON), pertenece a al género Flavivirus y a la familia Flaviviridae, en su ciclo de transmisión involucra mosquitos y aves, aunque en ocasiones es transmitido a otros hospederos entre ellos los humanos y equinos. En Yucatán se ha reportado la presencia de este virus en caballos, en aves migratorias y residentes, así como otros vertebrados en cautiverio. Debido a que el VON ya se halla en Yucatán y específicamente en la ciudad de Mérida es importante el conocer la bionomía del que se considera es el vector, el mosquito Culex quinquefasciatus. El objetivo general fue el determinar diferentes aspectos biológicos de Cx. quinquefasciatus en la ciudad de Mérida, así comó la incriminación de esta especie en la transmisión del VON en la región. Se realizaron muestreos en la ciudad utilizando métodos entomológicos como cajas rojas y trampas capturadoras; para la busqueda de la presencia del VON en los mosquitos se usó la técnica de RT-PCR. Por otra parte se estudió el biorritmo de picadura y se determino el estado trófico de las hembras capturadas. Así mismo, se obtuvo la sobrevida y la longitud del gonociclo mediante el método de series cruzadas de tiempo al comienzo y al final de la época de lluvias. Por último, se determinó las preferencias alimenticias y el rango de forrajeo usando PCR. Las colectas se realizaron del mes de enero al mes de diciembre diciembre de 2005, usando diferentes métodos: en las trampas capturadoras se colectaron un total de 4 544 mosquitos machos y 11 722 hembras, siendo el horario de mayor captura después de la las 12 de la noche, el 91% fueron hembras no alimentadas. Con respecto a las colectas en sitios de reposo se obtuvieron 9 099 machos y 4 856 hembras y el 35% fueron hembras alimentadas, el mes donde se obtuvieron más mosquitos fue agosto. Con respecto a la búsqueda del VON se probaron 685 grupos de mosquitos, hallándose seis muestras con bandas de igual peso molecular que el VON no se pudo demostrar la presencia de este virus en Mérida. El gonociclo se calculó en 4 días mediante el método de series cruzadas en las dos épocas, así como por la oogénesis. En relación a las preferencias alimenticias se determinó que el 88.11 % de los mosquitos se alimentó de aves y el 11.89 % de mamíferos. Estos resultados demuestran que esta especie está bien adaptada al medio urbano y se considerada la principal especie en la trasnmisión de este virus a los vertebrados. Abstract The West Nile Virus (WNV) belongs to the family Flaviviridae, in its transmission cycle involves mosquitos and birds, although in occasions it is transmitted to other hosts like humans and horses. In Yucatan the presence of this virus has been reported in horses, in migratory birds and residents, as well as other vertebrates in captivity. Because is already in Yucatan and specifically in the city of Merida it is important knowing the bionomics of which is considered the printipal mosquito vector Culex quinquefasciatus. The general objective was determining different biological aspects of Cx. quinquefasciatus in Merida City, like incrimination of this specie in the transmission of the WNV in the area. Using differents emtolomogical methods like red boxes and Mosquito Magnets traps; for the search of the presence of the WNV in the mosquitos the technique of RT-PCR. On the other hand it was studied the and all the collected mosquitos female they were determined the trophic state in which were found. In this study was carried out by means of the method of crossed series of time at the beginning and the end of the rainy season the and the length of the gonotrophic cycle. Lastly it was determined the host preferences and the forage range using PCR. The mosquitos were collected during January to December of 2005, using different methods, in the capturing traps a total of 4 544 male mosquitos and 11 722 females were collected, being the schedule of more capture after 2400 hours. 91% was females not fed. With regard to the collections 9 099 males and 4 856 females and 35% were obtained they were female fed, the month where more mosquitos were captured it was August. With regard to the search of the WNV 685 groups of mosquitos were tested being six samples with bands of same molecular weight that the WNV although we could not de virus isolation in Merida. The gonotrophic cycle was calculated in 4 days by means of the method of crossed series in the two times, as well as for the oogenesis. The host preferences of this species were determined that 88.11% of the mosquitos was fed of avians and 11.89% of mammals. These results demonstrate that this species has good adaptation to the urban means and is considered in the transmission from this virus to vertebrates

Mosquitos domiciliarios (Díptera: culicidae) y su relación como vectores de arbovirus en la ciudad de Mérida, Yucatán, México

Tesis (Maestría en Ciencias con Especialidad en Entomología Médica) UANLUANLhttp://www.uanl.mx

The neovolcanic axis is a barrier to gene flow among Aedes aegypti populations in Mexico that differ in vector competence for Dengue 2 virus.

The Neovolcanic axis (NVA) traverses Mexico at the 19th parallel and is considered to be a geographic barrier to many species. We have demonstrated that the intersection of the NVA with the coast in Veracruz state is a barrier to gene flow in Ae. aegypti. This was unexpected because the intersection of the NVA with the Pacific Coast is not a barrier to gene flow. Further studies to identify the actual mechanism(s) that is(are) contributing to the lack of gene flow will provide important information on the trafficking potential of Ae. aegypti, which will be of great value to Ae. aegypti control programs. There are significant differences in vector competence for dengue virus between mosquitoes north and south of the NVA, but the epidemiological significance of these finding remains to be determined. Future studies will determine if, for example, the genes that condition midgut infection and vector competence of Ae. aegypti populations provide biomarkers for risk of dengue transmission. Such biomarkers could be of great value to control programs in resource limited environments by allowing targeting of vector control efforts to areas at most risk for epidemic dengue and dengue hemorrhagic fever

Parallel evolution of vgsc mutations at domains IS6, IIS6 and IIIS6 in pyrethroid resistant Aedes aegypti from Mexico

Aedes aegypti is the primary urban mosquito vector of viruses causing dengue, Zika and chikungunya fevers –for which vaccines and efective pharmaceuticals are still lacking. Current strategies to suppress arbovirus outbreaks include removal of larval-breeding sites and insecticide treatment of larval and adult populations. Insecticidal control of Ae. aegypti is challenging, due to a recent rapid global increase in knockdown-resistance (kdr) to pyrethroid insecticides. Widespread, heavy use of pyrethroid spacesprays has created an immense selection pressure for kdr, which is primarily under the control of the voltage-gated sodium channel gene (vgsc). To date, eleven replacements in vgsc have been discovered, published and shown to be associated with pyrethroid resistance to varying degrees. In Mexico, F1,534C and V1,016I have co-evolved in the last 16 years across Ae. aegypti populations. Recently, a novel replacement V410L was identifed in Brazil and its efect on vgsc was confrmed by electrophysiology. Herein, we screened V410L in 25 Ae. aegypti historical collections from Mexico, the frst heterozygote appeared in 2002 and frequencies have increased in the last 16 years alongside V1,016I and F1,534C. Knowledge of the specifc vgsc replacements and their interaction to confer resistance is essential to predict and to develop strategies for resistance management

Universal primers for the amplification and sequence analysis pf actin-1 from diverse mosquito species

We report the development of universal primers for the reverse-transcription polymerase chain reaction (RT-PCR) amplification and nucleotide sequence analysis of actin cDNAs from taxonomically diverse mosquito species. Primers specific to conserved regions of the invertebrate actin-1 gene were designed after actin cDNA sequences of Anopheles gambiae, Bombyx mori, Drosophila melanogaster, and Caenorhabditis elegans. The efficacy of these primers was determined by RT-PCR with the use of total RNA from mosquitoes belonging to 30 species and 8 genera (Aedes, Anopheles, Culex, Deinocerites, Mansonia, Psorophora, Toxorhynchites, and Wyeomyia). The RT-PCR products were sequenced, and sequence data were used to design additional primers. One primer pair, denoted as Act-2F (5′-ATGGTCGGYATGGGNCAGAAGGACTC-3′) and Act-8R (5′-GATTCCATACCCAGGAAG-GADGG-3′), successfully amplified an RT-PCR product of the expected size (683-nt) in all mosquito spp. tested. We propose that this primer pair can be used as an internal control to test the quality of RNA from mosquitoes collected in vector surveillance studies. These primers can also be used in molecular experiments in which the detection, amplification or silencing of a ubiquitously expressed mosquito housekeeping gene is necessary. Sequence and phylogenetic data are also presented in this report

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

West Nile Virus Survey of Birds, Horses, and Mosquitoes of the Pacific Coast, Southern Mexico

Abstract. Serology of West Nile virus vectors and non-human reservoirs was surveyed at Acapulco, Jose Azueta, and Ometepec, three Pacific Coast localities of Guerrero State, Mexico. The objectives of this study were to use enzyme-linked immnosorbent assay (ELISA) to assess West Nile virus antibodies of bird and equine serum samples and use reverse transcription of polymerase chain reaction (RT-PCR) to detect the virus in field-collected resting mosquitoes. Forty birds trapped using mist nets yielded 10% seroprevalence. Similarly, 18.6% of 102 equine blood samples had West Nile virus. In addition, 4,854 mosquitoes were caught using motorized backpack aspirators and grouped into 116 pools. Of the 16 species and seven genera, no mosquito was positive for West Nile virus. Our study demonstrated West Nile virus seroprevalence on resident birds and equines in Guerrero State, Mexico

Metabarcoding: A Powerful Yet Still Underestimated Approach for the Comprehensive Study of Vector-Borne Pathogen Transmission Cycles and Their Dynamics

The implementation of sustainable control strategies aimed at disrupting the transmission of vector-borne pathogens requires a comprehensive knowledge of the vector ecology in the different eco-epidemiological contexts, as well as the local pathogen transmission cycles and their dynamics. However, even when focusing only on one specific vector-borne disease, achieving this knowledge is highly challenging, as the pathogen may exhibit a high genetic diversity and multiple vector species or subspecies and host species may be involved. In addition, the development of the pathogen and the vectorial capacity of the vectors may be affected by their midgut and/or salivary gland microbiome. The recent advent of Next-Generation Sequencing (NGS) technologies has brought powerful tools that can allow for the simultaneous identification of all these essential components, although their potential is only just starting to be realized. We present a metabarcoding approach that can facilitate the description of comprehensive host-pathogen networks, integrate important microbiome and coinfection data, identify at-risk situations, and disentangle the transmission cycles of vector-borne pathogens. This powerful approach should be generalized to unravel the transmission cycles of any pathogen and their dynamics, which in turn will help the design and implementation of sustainable, effective, and locally adapted control strategies

Fecundity and morphological description of the eggs of Psorophora cyanescens (Coquillett, 1902) (Diptera: Culicidae) by scanning electron microscopy

Taxonomic studies on mosquitoes are based on the morphological description of larvae and adults. However, few studies have focused on the morphological description of eggs despite their taxonomic value. The description of mosquito eggs by scanning electron microscopy (SEM) allows more detailed descriptions of the ornamentation of the egg, which can provide diagnostic characters of the species. The objective of the work was to describe the eggs of Psorophora cyanescens by SEM and provide fecundity data for the species. In general, Ps. cyanescens eggs are elliptical and very wide. The exochorion is characterized by polygon pattern, where each polygon consists of longitudinal ridges joined by cross-ridges defining regular "hexagonal" areas. Each longitudinal ridge consisting by a small tubercle. The small tubercles are irregular, rectangular, rounded, or tubular. The ornamentation of the exochorion also has long and conical tubercles throughout the egg region. The micropylar apparatus located in the anterior region of the egg has a prominent, continuous and thickness collar. Psorophora cyanescens laid mature eggs at 2.5 days post-feeding. The mean number of eggs per female was 82.20 (± 13.31). This is the first study that describes the ultrastructure of the morphology of the eggs of Ps. cyanescens by SEM. With the contribution of the present work, there are five species of the genus Psorophora whose eggs morphology is described by SEM: Ps. albigenu, Ps. albipes, Ps. columbiae, Ps. cyanescens, and Ps. ferox.Los estudios taxonómicos sobre mosquitos se basan en la descripción morfológica de larvas y adultos. Sin embargo, son pocos los estudios enfocados en la descripción morfológica de los huevos a pesar de su valor taxonómico. La descripción de los huevos de mosquitos mediante microscopía electrónica de barrido (MEB) permite obtener imágenes más detalladas de la ornamentación del huevo, los cuales pueden proporcionar caracteres diagnósticos de la especie. El objetivo del trabajo fue describir los huevos de Psorophora cyanescens por MEB y proporcionar datos de fecundidad de la especie. En general, los huevos de Ps. cyanescens son de forma elíptica y muy anchos. El exocorión se caracteriza por un patrón de polígono, donde cada polígono consta de crestas longitudinales unidas por crestas cruzadas que definen áreas "hexagonales" regulares. Cada cresta longitudinal consiste en un pequeño tubérculo. Los pequeños tubérculos son irregulares, rectangulares, redondeados o tubulares. La ornamentación del exocorión también presenta largos tubérculos cónicos en toda la región del huevo. El aparato micropilar ubicado en la región anterior del huevo tiene un collar prominente, continuo y grueso. Psorophora cyanescens puso huevos maduros a los 2.5 días después de la alimentación sanguínea. El número promedio de huevos por hembra fue de 82.20 (± 13.31). Este es el primer estudio que describe la ultraestructura de la morfología de los huevos de Ps. cyanescens mediante MEB. Con el aporte del presente trabajo, son cinco las especies del género Psorophora que cuentan con la descripción de la morfología de los huevos mediante MEB: Ps. albigenu, Ps. albipes, Ps. columbiae, Ps. cyanescens, and Ps. ferox