Nohemi Cigarroa-Toledo

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.

Vacant Lots: Productive Sites for Aedes (Stegomyia) aegypti (Diptera: Culicidae) in Mérida City, México

ABSTRACT We assessed the potential for vacant lots and other nonresidential settings to serve as source environments for Aedes (Stegomyia) aegypti (L.) (Diptera: Culicidae) in Mérida City, México. Mosquito immatures were collected, during November 2011–June 2013, from residential premises (n = 156 site visits) and nonresidential settings represented by vacant lots (50), parking lots (18), and streets or sidewalks (28). Collections totaled 46,025 mosquito immatures of 13 species. Ae. aegypti was the most commonly encountered species accounting for 81.0% of total immatures, followed by Culex quinquefasciatus Say (12.1%). Site visits to vacant lots (74.0%) were more likely to result in collection of Ae. aegypti immatures than residential premises (35.9%). Tires accounted for 75.5% of Ae. aegypti immatures collected from vacant lots. Our data suggest that vacant lots should be considered for inclusion in mosquito surveillance and control efforts in Mérida City, as they often are located near homes, commonly have abundant vegetation, and frequently harbor accumulations of small and large discarded water-holding containers that we now have demonstrated to serve as development sites for immature mosquitoes. In addition, we present data for associations of immature production with various container characteristics, such as storage capacity, water quality, and physical location in the environment.

Urban Mosquito Fauna in Mérida City, México: Immatures Collected from Containers and Storm-Water Drains/Catch Basins

Abstract. We examined the species composition and temporal occurrence of immature mosquitoes in containers and storm-water drains/catch basins from November 2011 to June 2013 in Mérida City, México. A wide range of urban settings were examined, including residential premises, vacant lots, parking lots, and streets or sidewalks with storm-water drains/catch basins. In total, 111,776 specimens of 15 species were recorded. The most commonly collected species were Aedes (Stegomyia) aegypti (L.) (n = 60,961) and Culex quinquefasciatus Say (45,702), which together accounted for 95.4% of the immatures collected. These species were commonly encountered during both rainy and dry seasons, whereas most other mosquito species were collected primarily during the rainy season. Other species collected were Aedes (Howardina) cozumelensis Diaz Najera, Aedes (Ochlerotatus) taeniorhynchus (Wiedemann), Aedes (Ochlerotatus) trivittatus (Coquillett), Culex coronator Dyar and Knab, Culex interrogator Dyar and Knab, Culex lactator Dyar and Knab, Culex nigripalpus Theobald, Culex salinarius Coquillett, Culex tarsalis Coquillett, Culex thriambus Dyar, Haemagogus equinus Theobald, Limatus durhamii Theobald, and Toxorhynchites rutilus (Coquillett). The greatest number of species was recorded from vacant lots (n = 11), followed by storm-water drains/catch basins (nine) and residential premises (six). Our study demonstrated that the heterogeneous urban environment in Mérida City supports a wide range of mosquito species, many of which are nuisance biters of humans and/or capable of serving as vectors of pathogens affecting humans or domestic animals. We also briefly reviewed the medical importance of the encountered mosquito species.

Serologic Evidence of Flavivirus Infections in Peridomestic Rodents in Merida, Mexico

Abstract We conducted surveillance for flavivirus infection in peridomestic rodents in Merida, Mexico in 2011–12. We captured 161 rodents inside private residences, using Sherman traps, including 86 house mice (Mus musculus) and 75 black rats (Rattus rattus). Serum from each animal was assayed by plaque reduction neutralization test (PRNT) using two vertebrate-specific flaviviruses (Apoi and Modoc viruses) and five mosquito-borne flaviviruses (dengue 2, dengue 4, St. Louis encephalitis virus, West Nile, and yellow fever viruses). Sixty-one (37.9%) rodents had antibodies that neutralized at least one virus. Prevalences for flaviviruses were 64.0% and 15.1% for black rats and house mice, respectively. None of the PRNT90 titers exceeded 80, and often they were highest for Modoc virus. These data suggest that a subset of rodents had been infected with Modoc virus or a closely related flavivirus that was not included in the PRNT analysis.

Mosquito fauna associated with Aedes aegypti (Diptera: Culicidae) in Yucatán State of southeastern México, and checklist with new records

Abstract As part of our routine surveillance for arboviruses transmitted by Aedes (Stegomyia) aegypti (L.) (Diptera: Culicidae) in Yucatán State, México, we regularly monitor the mosquito fauna that occurs in the region. In this study, immature and adult mosquitoes were collected at 60 study sites (including residential premises, churches, tourist areas, cemeteries, forested areas, and garbage dump sites) in Yucatán State from Jul 2014 to Dec 2015. In total, 4,062 larvae, 344 pupae, and 3,812 adults representing 7 genera and 27 species were collected. Three species had never before been identified in Yucatán State, and these are Aedes (Ochlerotatus) euplocamus Dyar & Knab, Aedes (Protomacleaya) podographicus Dyar & Knab, and Culex (Culex) declarator Dyar & Knab. The identification of these 3 species brings the current total of mosquito species recognized in Yucatán State to 52 (with 11 genera). Many of the mosquitoes collected in this study were temporally and spatially associated with Ae. aegypti.

Survey of mosquito-borne flaviviruses in the Cuitzmala River Basin, Mexico: do they circulate in rodents and bats?

BackgroundRNA viruses commonly infect bats and rodents, including mosquito-borne flaviviruses (MBFV) that affect human and animal health. Serological evidence suggests past interactions between these two mammalian orders with dengue viruses (DENV), West Nile virus (WNV), and yellow fever virus (YFV). Although in Mexico there are reports of these viruses in both host groups, we know little about their endemic cycles or persistence in time and space.MethodsRodents and bats were captured at the Cuitzmala River Basin on the Pacific coast of Jalisco state, Mexico, where MBFV, such as DENV, have been reported in both humans and bats. Samples were taken during January, June, and October 2014, at locations adjacent to the river. Tissue samples were collected from both bats and rodents and serum samples from rodents only. Highly sensitive serological and molecular assays were used to search for current and past evidence of viral circulation.ResultsOne thousand nine hundred forty-eight individuals were captured belonging to 21 bat and 14 rodent species. Seven hundred sixty-nine liver and 764 spleen samples were analysed by means of a specific molecular protocol used to detect flaviviruses. Additionally, 708 serum samples from rodents were examined in order to demonstrate previous exposure to dengue virus serotype 2 (which circulates in the region). There were no positive results with any diagnostic test.DiscussionTo our knowledge, this is the first survey of rodents and only the second survey of bats from the Pacific Coast of Mexico in a search for MBFV. We obtained negative results from all samples. We validated our laboratory tests with negative and positive controls. Our findings are consistent with other empirical and experimental studies in which these mammalian hosts may not replicate mosquito-borne flaviviruses or present low prevalence.ConclusionsTrue-negative results are essential for the construction of distribution models and are necessary to identify potential areas at risk. Negative results should not be interpreted as the local absence of MBFV in the region. On the contrary, we need to establish a long-term surveillance programme to find MBFV presence in the mosquito trophic networks, identifying the potential role of rodents and bats in viral dynamics.

Molecular detection of Dirofilaria immitis in dogs and mosquitoes in Tabasco, Mexico

Background & objectives: Dirofilaria immitis is a filarial nematode that causes heartworm disease in domestic as well as wild canines and felines; and cutaneous or pulmonary infections in humans. The purpose of the study was to estimate the prevalence of D. immitis in domestic dogs in Tabasco, Mexico and to assay mosquitoes temporally and spatially associated with dogs for evidence of infection. Methods: Blood was collected from 1050 dogs in 1039 houses during a random household survey performed in 2016 and 2017. Genomic DNA was extracted and assayed by polymerase chain reaction (PCR) using pan-filarial primers and various species-specific primers. Dog owners were interviewed using a structured questionnaire designed to collect information on factors that may impact the occurrence of filarial infection. The association between canine dirofilariasis prevalence and factors likely to impact infection was determined by univariate logistic regression analysis, followed by multivariate binomial logistic regression analysis. Indoor and outdoor resting mosquitoes were collected from houses by manual aspiration. Mosquitoes were identified according to species, homogenized and tested by PCR for filarial nematodes. Results: A total of 84 (8%) dogs were positive for D. immitis DNA, while 3 (0.3%) dogs contained Acanthocheilonema reconditum DNA. Several factors were significantly associated with D. immitis infection. For example, dogs that lived <100 m from a large source of open standing water were significantly more likely (p = 0.002) to become infected with D. immitis than other dogs. Additionally, dogs with infrequent or no anthelmintic treatment were significantly more likely (p = 0.0) to become infected than dogs that were regularly treated. The entomologic investigation yielded 2618 female mosquitoes from 14 species. Four pools of Culex quinquefasciatus were positive for D. immitis DNA and the minimum infection rate, calculated as the number of positive pools per 1000 mosquitoes tested, was 2.9. Interpretation & conclusion: The study identified several factors positively associated with an increased risk of D. immitis infection in domestic dogs in Tabasco and provides evidence that Cx. quinquefasciatus is potentially an important vector in this region. This information can be used by local veterinarians and dog owners to reduce the burden of D. immitis on canine health.

Perceptions of rodent-associated problems: an experience in urban and rural areas of Yucatan, Mexico

Rodents are a threat to agriculture and homes, and are a public health risk. Local perceptions about rodents and the damage they cause are vital, as a first step, to the design and implementation of rodent control or educational programs. A total of 111 interviews were conducted in two urban neighborhoods and two rural villages in Yucatan, Mexico. More than 90% of the interviewed inhabitants perceived rodents as a problem. The fear of rodents (57%), damage to food and stocks (56%), and damage to clothes (34%), were the most cited problems. In the urban neighborhoods, the use of rodent control methods was more frequent (57%) than in the villages (33%) in this study. In addition, the percentage of damage to domestic appliances was lower in villages (10%) than in neighborhoods (33%). Our preliminary results suggest that rodent pests represent a threat to human health and to human food security in the studied sites.

Mosquito Fauna in Home Environments of Tabasco, Mexico

Abstract. The aim of this study was to assess the biodiversity of mosquito species in houses of the five ecological regions and update the checklist of species previously reported in the state of Tabasco. In total, 325 dwellings at 43 localities in the five ecological regions were sampled. Collection was by entomological CDC backpack aspirator. The mosquitoes captured were identified using published taxonomic keys and the aid of a stereomicroscope. In total, 4,622 mosquitoes of 15 species in 10 genera were captured. Two species not previously reported in Tabasco State were found: Aedes (Ochlerotatus) angustivittatus (Dyar and Knab, 1907) and Mansonia dyari Belkin, Heinemann & Page, 1970. The mosquito fauna of the state of Tabasco, including the new species are 55 species in 17 genera. Most species found transmit diseases to humans and should be included in government mosquito control programs.

First Report of Chewing Lice Heterodoxus spiniger (Enderlein, 1909) and Trichodectes canis (De Geer, 1778) on Domestic Dogs at Tabasco, Mexico

Abstract. Lice are small wingless insects in the order Phthiraptera. Historically, the chewing louse Heterodoxus spiniger (Enderlein) was described from marsupials to the domestic dog (Canis lupus familiaris L.). Clinical manifestations of infestations by chewing lice are characterized by intense irritation and inflammation of the skin. We found six of 337 domiciled dogs from Tabasco State, Southeastern Mexico infested by chewing lice. Dogs were systematically examined, and ectoparasites were removed using a fine-toothed comb. Lice were deposited on a white sheet of paper and placed into plastic containers. The dog houses sampled were typically small and built of cement, and most inhabitants lived in vulnerable conditions. This is the first record of H. spiniger and the dog biting louse, Trichodectes canis (De Geer), infesting domestic dogs in Mexico. H. spiniger was present in the six dogs infested by lice, and T. canis co-infested one of them. Therefore, six infested dogs (100%) were positive for H. spiniger and one (17%) for T. canis. The importance of this report is that both ectoparasites are recognized as vectors of zoonotic diseases. Further studies are needed to clarify lice distribution, prevalence, and vectorial importance of neglected parasitic infections in Southeast Mexico.