Population dynamics of mosquito species in a West Nile virus endemic area in Madagascar.

Luciano Michaël Tantely,Sébastien Boyer,Catherine Cêtre-Sossah,Eric Cardinale,Tsiriniaina Rakotondranaivo

doi:10.1051/parasite/2017005

Abstract

Human and animal serological surveys suggest that West Nile virus (WNV) circulation is widely distributed in Madagascar. However, there are no reported West Nile fever outbreaks or epizootics in the country and only one fatal human case has been reported to date. Currently there is very limited information on the maintenance and the transmission of WNV in Madagascar and particularly on the mosquito species involved in transmission cycles. In 2014, we initiated a study to investigate mosquito species composition, relative abundance, and trophic behavior in Mitsinjo District close to Lake Kinkony, a WNV endemic area in north-western Madagascar. We collected a total of 2519 adult mosquitoes belonging to 21 different species. The most abundant species was Aedeomyia (Aedeomyia) madagascarica Brunhes, Boussès & da Cunha Ramos, which made up 83% of all the mosquitoes collected. Mosquito abundance was associated with proximity to the lake (Morafeno and Ankelimitondrotra). Additionally, a correlation was observed between the lake-side biotope and the abundance of mosquito vectors in Morafeno. WNV RNA was detected in one pool of Ae. madagascarica and one pool of Anopheles (Cellia) pauliani Grjebine, suggesting that these two species may be involved in the maintenance and/or transmission of WNV in Madagascar.

Highlights

West Nile virus (WNV) was first isolated from a woman with febrile illness in the West Nile district of Uganda in 1937 [54]
The species accumulation curve tending toward a plateau suggests that the number of species caught was approaching the total number of mosquito species in the area
Twenty-one mosquito species were collected in our study, a much larger number than the 14 species described in 2012 in the same area [5]

Summary

Introduction

Flavivirus) was first isolated from a woman with febrile illness in the West Nile district of Uganda in 1937 [54]. The virus is transmitted to humans through the bite of a mosquito that has previously acquired the virus by blood-feeding on infected birds. The role of mosquito species in the WNV transmission cycle was first demonstrated in the species Aedes albopictus (Skuse) in 1943 [47]. The first isolations from human sera occurred in Egypt and Israel in 1951 [20, 23]. In Africa, WNV is endemic and widely distributed [45] Subsequent events, including the emergence of WNV in North America in 1999, its spread westward across the United States, and throughout the western hemisphere from South America to Canada, as well as repeated outbreaks in Europe [11, 12], suggest that WNV has the largest geographical distribution among the arthropod-borne viruses [24].

Methods

Results

Conclusion