Reverse and Conventional Chemical Ecology Approaches for the Development of Oviposition Attractants for Culex Mosquitoes

Synthetic mosquito oviposition attractants are sorely needed for surveillance and control programs for Culex species, which are major vectors of pathogens causing various human diseases, including filariasis, encephalitis, and West Nile encephalomyelitis. We employed novel and conventional chemical ecology approaches to identify potential attractants, which were demonstrated in field tests to be effective for monitoring populations of Cx. p. quinquefasciatus in human dwellings. Immunohistochemistry studies showed that an odorant-binding protein from this species, CquiOBP1, is expressed in trichoid sensilla on the antennae, including short, sharp-tipped trichoid sensilla type, which house an olfactory receptor neuron sensitive to a previously identified mosquito oviposition pheromone (MOP), 6-acetoxy-5-hexadecanolide. CquiOBP1 exists in monomeric and dimeric forms. Monomeric CquiOBP1 bound MOP in a pH-dependent manner, with a change in secondary structure apparently related to the loss of binding at low pH. The pheromone antipode showed higher affinity than the natural stereoisomer. By using both CquiOBP1 as a molecular target in binding assays and gas chromatography-electroantennographic detection (GC-EAD), we identified nonanal, trimethylamine (TMA), and skatole as test compounds. Extensive field evaluations in Recife, Brazil, a region with high populations of Cx. p. quinquefasciatus, showed that a combination of TMA (0.9 µg/l) and nonanal (0.15 ng/µl) is equivalent in attraction to the currently used infusion-based lure, and superior in that the offensive smell of infusions was eliminated in the newly developed synthetic mixture

An unsettling explanation for the failure of skatole-baited ovitraps to capture Culex mosquitoes

Submitted by Kamylla Nascimento ([email protected]) on 2018-03-23T13:10:01Z No. of bitstreams: 1 PE-IAM (PREPRINT) - Ovitraps failure to capture mosquitoes .pdf: 1345690 bytes, checksum: 86bdba7a7a6069a3a716974419bdef92 (MD5)Approved for entry into archive by Kamylla Nascimento ([email protected]) on 2018-03-23T14:20:14Z (GMT) No. of bitstreams: 1 PE-IAM (PREPRINT) - Ovitraps failure to capture mosquitoes .pdf: 1345690 bytes, checksum: 86bdba7a7a6069a3a716974419bdef92 (MD5)Made available in DSpace on 2018-03-23T14:20:14Z (GMT). No. of bitstreams: 1 PE-IAM (PREPRINT) - Ovitraps failure to capture mosquitoes .pdf: 1345690 bytes, checksum: 86bdba7a7a6069a3a716974419bdef92 (MD5) Previous issue date: 2018Este trabalho foi apoiado pelo Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), sob o prêmio 407475 / 2012-5; Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco, sob premiaçãoAPQ-2141-4.00 / 12 PPSUS-FACEPE; e o Instituto Nacional de Alergia e Infecciosidade Doenças dos Institutos Nacionais de Saúde, sob o prêmio R01AI095514 e R21AI128931.Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil / Universidade Federal de Pernambuco. Centro Acadêmico do Agreste. Caruaru, PE, Brasil.Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.Universidade Federal de Santa Catarina. Centro de Ciências Biológicas. Departamento de Biologia Celular, Embriologia e Genética. Florianópolis, SC, Brazil.Universidade de São Paulo. Faculdade de Saúde Pública. Departamento de Epidemiologia. São Paulo, SP, Brazil.Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Departamento de Entomologia. Recife, PE, Brasil.University of California-Davis. Department of Molecular and Cellular Biology. Davis, CA, USA.Culex mosquitoes are primarily found in temperate and tropical regions worldwide where they play a crucial role as main vectors of filarial worms and arboviruses. In Recife, a northeast city in Brazil, high densities of Culex quinquefasciatus are often found in association with human populated areas. In marked contrast to another part of the city, field tests conducted in the neighborhood of Sítio dos Pintos showed that trapping of mosquitoes in skatole-baited ovitraps did not differ significantly from captures in control (water) traps. Thus, classical and molecular taxonomic approaches were used to analyze the Culex species circulating in Sítio dos Pintos. Results obtained from both approaches agreed on the co-circulation of Culex quinquefasciatus and Culex nigripalpus in three different areas of this neighborhood. What was initially considered as an unexpected failure of this lure turned out to be a more unsettling problem, i.e., the first report in Recife of Culex nigripalpus, a vector of Venezuelan equine encephalitis virus and West Nile virus. Unplanned urbanization processes close to remnants of the Atlantic forest, such as observed in Sítio dos Pintos, may have contributed to the introduction of Cx. nigripalpus in urban areas. This article is protected by copyright. All rights reserved

Does Zika virus infection affect mosquito response to repellents?

Submitted by Adagilson Silva ([email protected]) on 2017-06-27T12:01:18Z No. of bitstreams: 1 28205633 2017 doe-lea.oa.pdf: 886527 bytes, checksum: 4af0e3d37b395ff55a07d330c6ef8fea (MD5)Approved for entry into archive by Adagilson Silva ([email protected]) on 2017-06-27T12:15:07Z (GMT) No. of bitstreams: 1 28205633 2017 doe-lea.oa.pdf: 886527 bytes, checksum: 4af0e3d37b395ff55a07d330c6ef8fea (MD5)Made available in DSpace on 2017-06-27T12:15:07Z (GMT). No. of bitstreams: 1 28205633 2017 doe-lea.oa.pdf: 886527 bytes, checksum: 4af0e3d37b395ff55a07d330c6ef8fea (MD5) Previous issue date: 2017-02-16Fundação Oswaldo Cruz. Instituto Aggeu Magalhães. Recife, PE, BrasilThe World Health Organization (WHO) recommends that people travelling to or living in areas with Zika virus (ZIKV) outbreaks or epidemics adopt prophylactic measures to reduce or eliminate mosquito bites, including the use of insect repellents. It is, however, unknown whether repellents are effective against ZIKV-infected mosquitoes, in part because of the ethical concerns related to exposing a human subject's arm to infected mosquitoes in the standard arm-in-cage assay. We used a previously developed, human subject-free behavioural assay, which mimics a human subject to evaluate the top two recommended insect repellents. Our measurements showed that DEET provided significantly higher protection than picaridin provided against noninfected, host-seeking females of the southern house mosquito, Culex quinquefasciatus, and the yellow fever mosquito, Aedes aegypti. When tested at lower doses, we observed a significant reduction in DEET-elicited protection against ZIKV-infected yellow fever mosquitoes from old and recent laboratory colonies. The reduction in protection is more likely associated with aging than the virus infection and could be compensated by applying a 5x higher dose of DEET. A substantial protection against ZIKV-infected and old noninfected mosquitoes was achieved with 5% DEET, which corresponds approximately to a 30% dose in the conventional arm-in-cage assays