Biogeography of the two major arbovirus mosquito vectors, Aedes aegypti and Aedes albopictus (Diptera, Culicidae), in Madagascar

Abstract

BackgroundIn the past ten years, the Indian Ocean region has been the theatre of severe epidemics of chikungunya and dengue. These outbreaks coincided with a high increase in populations of Aedes albopictus that outcompete its sister taxon Aedes aegypti in most islands sampled. The objective of this work was to update the entomological survey of the two Aedes species in the island of Madagascar which has to face these arboviroses.MethodsThe sampling of Aedes mosquitoes was conducted during two years, from October 2007 to October 2009, in fifteen localities from eight regions of contrasting climates. Captured adults were identified immediately whereas immature stages were bred until adult stage for determination. Phylogenetic analysis was performed using two mtDNA genes, COI and ND5 and trees were constructed by the maximum likelihood (ML) method with the gene time reversible (GTR) model. Experimental infections with the chikungunya virus strain 06.21 at a titer of 107.5 pfu/mL were performed to evaluate the vector competence of field-collected mosquitoes. Disseminated infection rates were measured fourteen days after infection by immunofluorescence assay performed on head squashes.ResultsThe species Aedes aegypti was detected in only six sites in native forests and natural reserves. In contrast, the species Aedes albopictus was found in 13 out of the 15 sites sampled. Breeding sites were mostly found in man-made environments such as discarded containers, used tires, abandoned buckets, coconuts, and bamboo cuts. Linear regression models showed that the abundance of Ae. albopictus was significantly influenced by the sampling region (F = 62.00, p < 2.2 × 10-16) and period (F = 36.22, p = 2.548 × 10-13), that are associated with ecological and climate variations. Phylogenetic analysis of the invasive Ae. albopictus distinguished haplotypes from South Asia and South America from those of Madagascar, but the markers used were not discriminant enough to discern Malagasy populations. The experimental oral infection method showed that six Ae. albopictus populations exhibited high dissemination infection rates for chikungunya virus ranging from 98 to 100%.ConclusionIn Madagascar, Ae. albopictus has extended its geographical distribution whereas, Ae. aegypti has become rare, contrasting with what was previously observed. Changes are predominantly driven by human activities and the rainfall regime that provide suitable breeding sites for the highly anthropophilic mosquito Ae. albopictus. Moreover, these populations were found to be highly susceptible to chikungunya virus. In the light of this study, Ae. albopictus may have been involved in the recent outbreaks of chikungunya and dengue epidemics in Madagascar, and consequently, control measures should be promoted to limit its current expansion.

Role of Aedes aegypti (Linnaeus) and Aedes albopictus (Skuse) in local dengue epidemics in Taiwan

“…aegypti in 40 % of larval habitats [69]. However, as suggested by Paupy et al [70], the apparent coexistence of the two species could be a transient situation, followed by a reduction [71–73] or displacement [74, 75] of the resident species; interspecific larval competition for resources is the most likely reason for this process. Moreover, a few local studies have reported that the local spread of Ae.…”

Rapid evolution of reduced receptivity to interspecific mating in the dengue vector Aedes aegypti in response to satyrization by invasive Aedes albopictus

“…However, if the evolution of resistance to satyrization comes at a cost, resurgences in A. aegypti populations may not be stable, as the trait may decline or disappear if satyrization pressure eased. Resulting fluctuations in the relative abundances of the two species could on the one hand contribute to the patchy distribution patterns of these two species often observed where they co-occur around the world (Craig 1993; Benedict et al 2007; Higa et al 2010; Raharimalala et al 2012; Bargielowski et al 2013). On the other hand fluctuations in vector prevalence could also negatively impact disease transmission.…”

Genotypic and Phenotypic Characterization of Chikungunya Virus of Different Genotypes from Malaysia

“…This evolved adaptation will impact regions where Ae. albopictus populations are increasing [35], [36]. Where both genotypes co-exist, this may lead to displacement of Asian strains by ECSA strains.…”