Elsy P. Rosado-Paredes

Serologic Evidence of West Nile Virus Infection in Horses, Yucatan State, Mexico

Serum samples were obtained from 252 horses in the State of Yucatan, Mexico, from July to October 2002. Antibodies to West Nile virus were detected by epitope-blocking enzyme-linked immunosorbent assays in three (1.2%) horses and confirmed by plaque reduction neutralization test. We report the first West Nile virus activity in the State of Yucatan.

Longitudinal Studies of West Nile Virus Infection in Avians, Yucatán State, México

Following the introduction of West Nile virus (WNV) into North America in 1999, surveillance for evidence of infection with this virus in migratory and resident birds was established in Yucatán State, México in March 2000. Overall, 8611 birds representing 182 species and 14 orders were captured and assayed for antibodies to WNV. Of these, 5066 (59%) birds were residents and 3545 (41%) birds were migrants. Twenty-one (0.24%) birds exhibited evidence of flavivirus infection. Of these, 8 birds had antibodies to WNV by epitope-blocking enzyme-linked immunosorbent assay. Five (0.06%) birds (gray catbird, brown-crested flycatcher, rose-breasted grosbeak, blue bunting and indigo bunting) were confirmed to have WNV infections by plaque reduction neutralization test. The WNV-infected birds were sampled in December 2002 and January 2003. The brown-crested flycatcher and blue bunting presumably were resident birds; the other WNV seropositive birds were migrants. These data provide evidence of WNV transmission among birds in the Yucatán Peninsula.

Host-Feeding Preference of the Mosquito, Culex quinquefasciatus, in Yucatan State, Mexico

Abstract Studies were conducted to determine the host-feeding preference of Culex quinquefasciatus Say (Diptera: Culicidae) in relation to the availability of human and domestic animals in the city of Merida, Yucatan State, Mexico. Mosquitoes were collected in the backyards of houses using resting wooden boxes. Collections were made five times per week from January to December 2005. DNA was extracted from engorged females and tested by PCR using universal avian- and mammalian-specific primers. DNA extracted from avian-derived blood was further analyzed by PCR using primers that differentiate among the birds of three avian orders: Passeriformes, Columbiformes and Galliformes. PCR products obtained from mammalian-derived blood were subjected to restriction enzyme digestion to differentiate between human-, dog-, cat-, pig-, and horse-derived blood meals. Overall, 82% of engorged mosquitoes had fed on birds, and 18% had fed on mammals. The most frequent vertebrate hosts were Galliformes (47.1%), Passeriformes (23.8%), Columbiformes (11.2%) birds, and dogs (8.8%). The overall human blood index was 6.7%. The overall forage ratio for humans was 0.1, indicating that humans were not a preferred host for Cx. quinquefasciatus in Merida.

West Nile virus activity in mosquitoes and domestic animals in Chiapas, México.

Prior to 2006, West Nile virus (WNV) had not been definitively detected in Chiapas, the southernmost state of Mexico, although it circulates elsewhere in Mexico and Central America. We collected over 30,000 mosquitoes and blood-sampled 351 domestic animals in Chiapas in search for evidence of current or recent transmission of WNV. Two mosquito pools tested positive for WNV RNA and 17 domestic animals tested positive for specific WNV-neutralizing antibodies, including young animals (<1 year old) in four of five sampled locations. The two WNV-positive mosquito pools were collected on the Pacific coastal plain of Chiapas in June, 2006, and included a pool of Culex nigripalpus, a suspected vector of WNV, and a pool of Cx. interrogator. The sequence of a 537-nucleotide portion of a cDNA amplicon derived from the WNV NS5 gene from the Cx. interrogator pool contained a single silent nucleotide substitution when compared to WNV strain NY99.

Chikungunya Virus in Febrile Humans and Aedes aegypti Mosquitoes, Yucatan, Mexico.

Chikungunya virus (CHIKV) was isolated from 12 febrile humans in Yucatan, Mexico, in 2015. One patient was co-infected with dengue virus type 1. Two additional CHIKV isolates were obtained from Aedes aegypti mosquitoes collected in the homes of patients. Phylogenetic analysis showed that the CHIKV isolates belong to the Asian lineage.

Gonotrophic Cycle Estimate for Culex quinquefasciatus in Mérida, Yucatán, México

ABSTRACT West Nile virus (WNV) has been present in the Yucatán State, México, since 2002. Culex quinquefasciatus, one of the main vectors of WNV transmission in the United States, is also common in Mexico and may be a key vector of WNV transmission to humans in the Yucatán. The aim of this study was to determine the length of the gonotrophic cycle and the survival rates of Cx. quinquefasciatus from Mérida, Yucatán, during the rainy versus the dry season. Mosquitoes were collected during 25-day periods in October (rainy season) and in April (dry season), and captured females were classified by abdominal appearance (freshly fed, late-stage fed, half gravid, and subgravid). To determine the age structure as nulliparous and parous females and to calculate the gonotrophic cycle through a time series and the mosquito survival, we used Davidson formulae. Also, vitellogenesis analysis to monitor egg maturity was conducted during both seasons. Cross-correlation data suggested a similar length of the gonotrophic cycle (4 days) in both seasons. Oogenic development required a minimum of 72 h in each season. However, survival of the mosquito population collected in the rainy season was significantly higher (0.91) with a mean temperature of 28 ± 1.57°C than was survival in the dry season (0.78) with a mean temperature of 29 ± 1.10°C. Survival, although higher during the rainy season, did not influence the length of the gonotrophic cycle of Cx. quinquefasciatus in Yucatán.

Prevalencia de infección por el virus del Nilo Occidental en dos zoológicos del estado de Tabasco

Objective. To determine the prevalence of West Nile Virus (WNV) infection in animals, mosquitoes and employees from two zoos of Tabasco state, Mexico. Material and Methods. WNV antibodies were detected by blocking ELISA in serum samples from animals. Viral RNA was detected by RT-PCR from mosquitoes and serum samples from employees at “Yum-Ka” zoo. Results. Seroprevalence in birds was 25.65% (19/74) and 85% (6/7) in reptiles from “La Venta” zoo. Thirty-one percent of birds (50/160) and 34.48% mammals (16/29) at the “Yum-Ka” zoo, were seropositive. All human serum samples from Yum-ka zoo were negative by RT-PCR. A pool of mosquitoes (Culex quinquefasciatus) was positive for WNV. Conclusions. The presence of WNV antibodies in animals from both zoos and the detection of viral genome in mosquitoes demonstrate the presence of WNV in this region and indicates a potential risk of infection in animals and humans.

Antibodies to influenza and West Nile viruses in horses in Mexico

INFLUENZA A virus (IAV) (family Orthomyxoviridae) is a highly infectious respiratory pathogen of birds and mammals, including human beings and horses ([Palese and Shaw 2007][1]). The virus is classified into different subtypes based on the antigenic properties of the haemagglutinin (HA) and

Evidencia serológica de la infección por el Virus del Oeste del Nilo en caballos del estado de Yucatán, México

Se obtuvieron muestras de suero de 252 caballos en el estado de Yucatan, Mexico, de julio a octubre de 2002. Se determinaron en ellos anticuerpos contra el virus del Oeste del Nilo a traves del bloqueo de epitopes por ensayo inmunoenzimatico. Se observo serorreactividad en 3 (1.2%) caballos. Los resultados fueron confirmados a traves de la reduccion de neutralizacion de placas. Este es el primer reporte que demuestra la presencia del virus del Oeste del Nilo en el estado de Yucatan, Mexico.