Mosquito Fauna in the Mangroves of Yucatan, Mexico, and Identification of Alphavirus RNA.

The surveillance of arboviruses in mangrove mosquitoes is a neglected topic in Mexico. The Yucatan State is part of a peninsula and, therefore, is rich in mangroves along its coast. The purpose of the study was to identify alphavirus in the mosquito fauna of mangroves. Mosquitoes were captured in mangrove settings in seven communities in Yucatan between June 2019 and August 2021. From 1900 to 2200 h and from 0500 to 0800 h, mosquitoes were captured with a backpack-mounted aspirator. In total, 3,167 female mosquitoes of five genera and nine species were captured. Aedes taeniorhynchus and Anopheles crucians were the most abundant mosquitoes collected. Mosquitoes were sorted into 210 pools and tested by reverse transcription-polymerase chain reaction for alphavirus ribonucleic acid (RNA). Alphavirus RNA was found in Ae. taeniorhynchus, An. pseudopunctipennis, and An. crucians collected in the Celestun Mangrove. The community is part of the Ria Celestun Biosphere Reserve, and the presence arbovirus-infected mosquitoes could pose a health risk to residents and visitors alike in the area.

Infection, dissemination, and transmission efficiencies of Zika virus in Aedes aegypti after serial passage in mosquito or mammalian cell lines or alternating passage in both cell types.

BACKGROUND: Zika virus (ZIKV) is an arthropod-borne virus (arbovirus) with an urban transmission cycle that primarily involves humans and Aedes aegypti. Evidence suggests that the evolution of some arboviruses is constrained by their dependency on alternating between disparate (vertebrate and invertebrate) hosts. The goals of this study are to compare the genetic changes that occur in ZIKV after serial passaging in mosquito or vertebrate cell lines or alternate passaging in both cell types and to compare the replication, dissemination, and transmission efficiencies of the cell culture-derived viruses in Ae. aegypti. METHODS: An isolate of ZIKV originally acquired from a febrile patient in Yucatan, Mexico, was serially passaged six times in African green monkey kidney (Vero) cells or Aedes albopictus (C6/36) cells or both cell types by alternating passage. A colony of Ae. aegypti from Yucatan was established, and mosquitoes were challenged with the cell-adapted viruses. Midguts, Malpighian tubules, ovaries, salivary glands, wings/legs and saliva were collected at various times after challenge and tested for evidence of virus infection. RESULTS: Genome sequencing revealed the presence of two non-synonymous substitutions in the premembrane and NS1 regions of the mosquito cell-adapted virus and two non-synonymous substitutions in the capsid and NS2A regions of both the vertebrate cell-adapted and alternate-passaged viruses. Additional genetic changes were identified by intrahost variant frequency analysis. Virus maintained by continuous C6/36 cell passage was significantly more infectious in Ae. aegypti than viruses maintained by alternating passage and consecutive Vero cell passage. CONCLUSIONS: Mosquito cell-adapted ZIKV displayed greater in vivo fitness in Ae. aegypti compared to the other viruses, indicating that obligate cycling between disparate hosts carries a fitness cost. These data increase our understanding of the factors that drive ZIKV adaptation and evolution and underscore the important need to consider the in vivo passage histories of flaviviruses to be evaluated in vector competence studies.

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

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.

The Use of Insecticide-Treated Curtains for Control of Aedes aegypti and Dengue Virus Transmission in "Fraccionamiento" Style Houses in México.

Dengue, chikungunya, yellow fever, and Zika viruses transmitted by Aedes aegypti mosquitoes are major public health threats in the tropical and subtropical world. In México, construction of large tracts of "fraccionamientos" high density housing to accommodate population growth and urbanization has provided fertile ground for Ae. aegypti-transmitted viruses. We investigated the utility of pyrethroid-treated window curtains to reduce both the abundance of Ae. aegypti and to prevent dengue virus (DENV) transmission in fraccionamiento housing. Windows and doors of fraccionamiento homes in urban/suburban areas, where Ae. aegypti pyrethroid resistance associated with the Ile1016 knock down resistance (kdr) mutation in the voltage gated sodium channel gene was high, and in rural areas, where kdr resistance was low, were fitted with either insecticide-treated curtains (ITCs) or non-treated curtains (NTCs). The homes were monitored for mosquito abundance and DENV infection. ITCs reduced the indoor abundance of Ae. aegypti and the number of DENV-infected mosquitoes in homes in rural but not in urban/suburban study sites. The presence of non-treated screens also was associated with reduced numbers of mosquitoes in homes. "Super-infested" homes, yielding more than 50 mosquitoes, including DENV-infected mosquitoes, provide a significant public health risk to occupants, visitors, and people in neighboring homes.

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.

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

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.

Orthobunyavirus antibodies in humans, Yucatan Peninsula, Mexico.

We performed a serologic investigation to determine whether orthobunyaviruses commonly infect humans in the Yucatan Peninsula of Mexico. Orthobunyavirus-specific antibodies were detected by plaque reduction neutralization test in 146 (18%) of 823 persons tested. Further studies are needed to determine health risks for humans from this potentially deadly group of viruses.