Biology of Mosquitoes That Are Potential Vectors of Rift Valley Fever Virus in Different Biotopes of the Central Highlands of Madagascar

Abstract

There were epidemic-epizootics of Rift Valley Fever (RVF) affecting humans and cattle in Madagascar in the district of Anjozorobe in 2008. Little is known about the role of Malagasy mosquitoes in the circulation of RVF virus. Therefore, we investigated the species diversity, dynamics and biology of potential RVF virus vectors in the rainforest, rainforest edge (village of Anorana), and savanna biotope (village of Antanifotsy) of this district between November 2008 and July 2010. We captured 56,605 adults of 35 different species. Anopheles squamosus (Theobald), Anopheles coustani (Laveran), Culex antennatus (Becker), Culex pipiens (L.), and Culex univittatus (Theobald) were the most abundant during the rainy season with Cx. pipiens the most abundant species in the rainforest (47%), and An. squamosus the most abundant species in the rainforest edge and in the savanna biotope (56%, 60%, respectively). Only Cx. univittatus was abundant in the dry season. The parous rate was > 60% throughout the rainy season for An. squamosus and it was > 50% from the middle to the end of the rainy season for Cx. pipiens. Two additional species have been found only at larval stage. Cattle were the most attractive bait for all species, followed by sheep and poultry. Human was the least attractive for all species. Most of the 163 bloodmeals tested were taken from cattle. Three were from poultry, one was from dog and one was a mixed bloodmeal taken from sheep and cattle. These results on vectorial capacity parameters may allow considering the involvement of mosquito transmission of the virus in the district of Anjozorobe during the recent epidemic-epizootic.

A Review of Mosquitoes Associated with Rift Valley Fever Virus in Madagascar

“…On a global basis, the occurrence and spread of the RVF outbreaks on the African mainland and the Arabia Peninsula are variable and found in different ecoclimatic zones; vector species and vector capacity are influenced by ecological, 14 behavioral, 15 and RVFV molecular factors. 16,17 For example, in an arid area, such as the Arabian Peninsula, RVFV transmission by mosquitoes is related to rainfall and water runoff management, with temporary rain pools and floodplains representing favorable vector breeding sites.…”

“…33 Most of these species have zoophilic behavior (cattle, sheep, and goat), and some of them are described opportunistic anthropophilic feeders. 15,34,35 These taxa belong to the genera Aedes, Anopheles, Culex, Eretmapodites, and Mansonia following traditional morphological classifications. 36,37 In Madagascar, six species of Aedes fall into the vector, candidate vector, and potential vector categories associated with RVFV.…”

“…uniformis. 9,42 Recently considered as an RVFV candidate vector, 15 Cx. antennatus also has a high vector competence.…”

“…Moreover, this zooantropophilic species is present and abundant in all five biogeographical domains of Madagascar. Recently considered as an RVFV candidate vector, 15 Cx. antennatus has high vector competence.…”

“…squamosus are the most abundant Anopheles taxa in Madagascar, both being zoophilic with broad distributions across the island. 12,15 Information is currently not available on the level of vector competence, and hence, both species remain RVFV candidate vectors. 15 Using this proposed system of categorization, seven other zooanthropophilic species should be included: Cx.…”