Estudo bioecológico do Aedes (Stegomyia) aegypti (Diptera: Culicidae) no aquipélago da Madeira

Desde o seu registo no Funchal em 2005 que o Aedes aegypti, principal vector do vírus da dengue e da febre amarela, tem vindo a expandir-se territorialmente apesar da implementação de medidas de controlo pelas autoridades regionais. Face a esta situação, tornava-se necessário conhecer a bioecologia desta espécie no Arquipélago da Madeira, de forma a criar um planeamento o mais adequado possível para o seu controlo. De forma a contribuir para aquele conhecimento, o presente trabalho teve como principais objectivos o estudo da variação sazonal, a caracterização dos biótopos larvares e a detecção de eventuais preferências, a determinação das associações larvares e o padrão de distribuição do Aedes aegypti no Arquipélago da Madeira. Os trabalhos de campo realizaram-se entre Janeiro e Agosto de 2009, sendo colocadas 53 armadilhas para a detecção de posturas (oviposição), feitas 395 observações e prospectados os potenciais biótopos. O estudo revelou a presença da espécie apenas em três dos pontos de amostragem localizados nos concelhos de Funchal e de Câmara de Lobos entre, 0 e 235 metros de altitude. Aedes aegypti demonstrou uma variação acentuada na sua actividade ao longo deste período, sendo baixa na estação fria e alta na estação quente, com um pico em Agosto. O estudo demonstrou igualmente que o Aedes aegypti colonizou 7,14% dos biótopos larvares detectados na área infestada, com preferência por biótopos larvares do tipo artificial, do subtipo plástico. Os biótopos larvares de Aedes aegypti eram maioritariamente de pequena capacidade, dependentes da água de rega, com água incolor e límpida e com presença de matéria orgânica vegetal.Since its registration in Funchal in 2005, that Aedes aegypti, the principal vector of dengue and yellow fever, has expanded territorially despite the implementation of control measures by the regional authorities. Given this situation, it became necessary to understand the bio-ecology of this species, Aedes aegypti, in the Archipelago, and thus, implementing a plan could be the most appropriate to keep it under control. In order to increase such knowledge, the present study had as its main objective the study of seasonal variation, the characterization of larval biotopes and the detection of any preferences, to determine the associations and larval distribution patterns of Aedes aegypti in the Archipelago. The fieldwork took place between January and August 2009 and 53 traps were placed for the egg (oviposition) detection, 395 observations were made and potential biotopes prospected. The study revealed the presence of the species in only three sampling points located in the districts of Funchal and Câmara de Lobos between 0 and 235 meters above sea level. Aedes aegypti has shown a marked variation in its activity during this period, which is low in cold temperatures, high in hot season, with its peak in August. The study also showed that Aedes aegypti colonized 57.14% of the samples detected in the larval infested area, with a preference for larval biotopes of the artificial type and subtype plastic. Aedes aegypti preferred larval biotopes with small quantities of water, dependent on irrigation water, with colourless water and the presence of vegetal matter

Potential of Aedes aegypti populations in Madeira Island to transmit dengue and chikungunya viruses

Abstract Background Aedes spp. mosquitoes mainly transmit the arboviruses dengue virus (DENV) and chikungunya virus (CHIKV) in urban areas, causing a severe public health problem. In 2012–2013, a major dengue outbreak occurred on Madeira Island where the mosquito Aedes aegypti was the only vector. Up to now, the competence of Ae. aegypti populations from Madeira to transmit DENV or CHIKV remains unknown. This study aimed to assess experimentally the ability of Ae. aegypti populations from Madeira to transmit these viruses. Results By orally exposing mosquitoes to CHIKV (NC/2011-568) and DENV-2 (Bangkok), the vector competence of two field-collected Ae. aegypti populations, i.e. Funchal and Paúl do Mar, was evaluated. We found that both populations were similarly infected and ensured the dissemination and transmission of CHIKV at the same rates. With DENV-2, viral dissemination was significantly higher in the Funchal population compared to Paúl do Mar. We found no significant differences in transmission rates between populations. Conclusions To our knowledge, this study has demonstrated for the first time the ability of temperate European Ae. aegypti populations from Madeira to transmit DENV and CHIKV. As our results suggest, there is a potential risk for the local transmission of DENV and CHIKV if introduced to Madeira or continental Europe where Aedes albopictus is present. Our results highlight the need for continuing vector surveillance and control on Madeira Island to future-proof the Island against mosquito-borne epidemics

Origin and expansion of the mosquito Aedes aegypti in Madeira Island (Portugal)

Abstract Historically known as the yellow fever mosquito, Aedes aegypti invaded Madeira Island in 2005 and was the vector of the island’s first dengue outbreak in 2012. We have studied genetic variation at 16 microsatellites and two mitochondrial DNA genes in temporal samples of Madeira Island, in order to assess the origin of the invasion and the population structure of this mosquito vector. Our results indicated at least two independent colonization events occurred on the island, both having a South American source population. In both scenarios, Venezuela was the most probable origin of these introductions, a result that is in accordance with the socioeconomic relations between this country and Madeira Island. Once introduced, Ae. aegypti has rapidly expanded along the southern coast of the island and reached a maximum effective population size (N e ) in 2012, coincident with the dengue epidemic. After the outbreak, there was a 10-fold reduction in N e estimates, possibly reflecting the impact of community-based vector control measures implemented during the outbreak. These findings have implications for mosquito surveillance not only for Madeira Island, but also for other European regions where Aedes mosquitoes are expanding