Convergent habitat segregation of Aedes aegypti and Aedes albopictus (Diptera : Culicidae) in southeastern Brazil and Florida

During the rainy season of 2001, the incidence of the dengue vectors Aedes aegypti and Ae. albopictus was examined in different habitats of two cities (Rio de Janeiro and Nova Iguacu) in Rio de Janeiro State, Brazil, and in two cities (Palm Beach and Boca Raton) in Florida. Oviposition trap collections were performed in urban, suburban, and rural habitats in both areas. Our hypothesis that the abundances and frequencies of occurrence of Ae. aegypti and Ae albopictus are affected in opposite ways by increasing urbanization was only partially supported. City, habitat, and their interaction significantly affected the abundance of both species. Cities with high abundance of Ae. aegypti also had a high abundance of Ae. albopictus. The two species were most abundant in the cities of Rio de Janeiro state and the lowest in Boca Raton. Habitat bad a significant but opposite effect on the abundances of Ae. aegypti and Ae. albopictus. In general, Ae. aegypti was most prevalent in highly urbanized areas and Ae. albopictus in rural, suburban, and vegetated urban areas in Rio de Janeiro state and Florida. However, abundances of the two species were similar in most suburban areas. Analyses of frequencies of occurrence showed an unexpected high level of co-occurrence of both species in the same oviposition trap. Despite the different geographical origins of Ae. albopictus in Brazil and the United States, the habitats used by this recent invader are remarkably similar in the two countries

The introduction of dengue follows transportation infrastructure changes in the state of Acre, Brazil : a network-based analysis.

Human mobility, presence and passive transportation of Aedes aegypti mosquito, and environmental characteristics are a group of factors which contribute to the success of dengue spread and establishment. To understand this process, we assess data from dengue national and municipal basins regarding population and demographics, transportation network, human mobility, and Ae. aegypti monitoring for the Brazilian state of Acre since the first recorded dengue case in the year 2000 to the year 2015. During this period, several changes in Acre?s transport infrastructure and urbanization have been started. To reconstruct the process of dengue introduction in Acre, we propose an analytic framework based on concepts used in malaria literature, namely vulnerability and receptivity, to inform risk assessments in dengue-free regions as well as network theory concepts for disease invasion and propagation. We calculate the probability of dengue importation to Acre from other Brazilian states, the evolution of dengue spread between Acrean municipalities and dengue establishment in the state. Our findings suggest that the landscape changes associated with human mobility have created favorable conditions for the establishment of dengue virus transmission in Acre. The revitalization of its major roads, as well as the increased accessibility by air to and within the state, have increased dengue vulnerability. Unplanned urbanization and population growth, as observed in Acre during the period of study, contribute to ideal conditions for Ae. aegypti mosquito establishment, increase the difficulty in mosquito control and consequently its local receptivity

Seasonal Differences in Density But Similar Competitive Impact of Aedes albopictus (Skuse) on Aedes aegypti (L.) in Rio de Janeiro, Brazil.

Previous studies have shown that the negative effects of density of Ae. albopictus on Ae. aegypti exceed those of Ae. aegypti on Ae. albopictus for population growth, adult size, survivorship, and developmental rate. This competitive superiority has been invoked to explain the displacement of Ae. aegypti by Ae. albopictus in the southeastern USA. In Brazil, these species coexist in many vegetated suburban and rural areas. We investigated a related, but less-well-studied question: do effects of Ae. albopictus on Ae. aegypti larval development and survival occur under field conditions at realistic densities across multiple seasons in Brazil? We conducted additive competition experiments in a vegetated area of Rio de Janeiro where these species coexist. We tested the hypothesis that Ae. aegypti (the focal species, at a fixed density) suffers negative effects on development and survivorship across a gradient of increasing densities of Ae. albopictus (the associate species) in three seasons. The results showed statistically significant effects of both season and larval density on Ae. aegypti survivorship, and significant effects of season on development rate, with no significant season-density interactions. Densities of Aedes larvae in these habitats differed among seasons by a factor of up to 7x. Overall, Spring was the most favorable season for Ae. aegypti survivorship and development. Results showed that under natural conditions the negative competitive effects of Ae. albopictus on Ae. aegypti were expressed primarily as lower survivorship. Coexistence between Ae. aegypti and Ae. albopictus in vegetated areas is likely affected by seasonal environmental differences, such as detrital resource levels or egg desiccation, which can influence competition between these species. Interactions between these Aedes are important in Brazil, where both species are well established and widely distributed and vector dengue, Zika and chikungunya viruses

Competition experiment results.

<p>Mean (± 2 SE) for competition treatments for mean instar of <i>Ae</i>. <i>aegypti</i> and survivorship after 7 days of experiment in the Autumn, Spring and Summer.</p

Two-way ANOVA for the effect of <i>Aedes albopictus</i> density and season on the mean larval survivorship and developmental progress of <i>Aedes aegypti</i> after 7 days (mean instar).

<p>Two-way ANOVA for the effect of <i>Aedes albopictus</i> density and season on the mean larval survivorship and developmental progress of <i>Aedes aegypti</i> after 7 days (mean instar).</p

Pupal productivity and Climate data during the colonization period.

<p>Pupal productivity of <i>Ae</i>. <i>aegypti</i> (a) and <i>Ae</i>. <i>albopictus</i> (b), mean daily temperature (c) and daily rainfall (d) during the 30-day period of colonization in the Autumn, Spring and Summer.</p

Relative abundance of the pupal productivity for each mosquito species and mean (standard error) pupae produced per vase at the end of the 30 days period of colonization in the Autumn, Spring and Summer.

<p>Relative abundance of the pupal productivity for each mosquito species and mean (standard error) pupae produced per vase at the end of the 30 days period of colonization in the Autumn, Spring and Summer.</p

Kruskal-Wallis test for significant differences in pupal productivity between Autumn, Spring and Summer colonization period, and Mann-Whitney pairwise comparisons with Bonferroni correction.

<p>Mann-Whitney tests were used for comparisons between <i>Ae</i>. <i>aegypti</i> and <i>Ae</i>. <i>albopictus</i> (overall and in each season).</p

Climate normals (1961–1990) for the city of Rio de Janeiro.

<p>Instituto Nacional de Meteorologia—Brazilian National Institute of Meteorology, available at <a href="http://www.inmet.gov.br/" target="_blank">http://www.inmet.gov.br/</a>.</p

Larval and pupal productivity during the colonization period defined the Baseline number for the larval manipulation experiments.

<p>Larval and pupal productivity during the colonization period defined the Baseline number for the larval manipulation experiments.</p