Circadian activity of Culicoides oxystoma (Diptera: Ceratopogonidae), potential vector of bluetongue and African horse sickness viruses in the Niayes area, Senegal.

Moussa Fall,Claire Garros,Geoffrey Gimonneau,Maryam Diarra,Assane G Fall,Thierry Baldet,Ousmane Faye,Thomas Balenghien,Jérémy Bouyer,Momar T Seck,Mame T Bakhoum

doi:10.1007/s00436-015-4534-8

Abstract

Culicoides biting midges (Diptera: Ceratopogonidae) are important vectors of arboviruses in Africa. Culicoides oxystoma has been recently recorded in the Niayes region of Senegal (West Africa) and its high abundance on horses suggests a potential implication in the transmission of the African horse sickness virus in this region. This species is also suspected to transmit bluetongue virus to imported breeds of sheep. Little information is available on the biology and ecology of Culicoides in Africa. Therefore, understanding the circadian host-seeking activity of this putative vector is of primary importance to assess the risk of the transmission of Culicoides-borne pathogens. To achieve this objective, midges were collected using a sheep-baited trap over two consecutive 24-h periods during four seasons in 2012. A total of 441 Culicoides, belonging to nine species including 418 (94.8 %) specimens of C. oxystoma, were collected. C. oxystoma presented a bimodal circadian host-seeking activity at sunrise and sunset in July and was active 3 h after sunrise in April. Daily activity appeared mainly related to time periods. Morning activity increased with the increasing temperature up to about 27 °C and then decreased with the decreasing humidity, suggesting thermal limits for C. oxystoma activity. Evening activity increased with the increasing humidity and the decreasing temperature, comprised between 20 and 27 °C according to seasons. Interestingly, males were more abundant in our sampling sessions, with similar activity periods than females, suggesting potential animal host implication in the facilitation of reproduction. Finally, the low number of C. oxystoma collected render practical vector-control recommendations difficult to provide and highlight the lack of knowledge on the bio-ecology of this species of veterinary interest.Electronic supplementary materialThe online version of this article (doi:10.1007/s00436-015-4534-8) contains supplementary material, which is available to authorized users.

Highlights

Culicoides biting midges (Diptera: Ceratopogonidae) are small hematophagous insects known for their veterinary importance
African horse sickness (AHS) is one of the most important and lethal infectious diseases endemic in sub-Saharan Africa affecting equids leading to high mortality rates in susceptible horses (>90 %)
This study aims to describe the circadian host-seeking activity of C. oxystoma according to abiotic conditions observed during four seasons in Senegal

Summary

Introduction

Culicoides biting midges (Diptera: Ceratopogonidae) are small hematophagous insects known for their veterinary importance. Females of several species are implicated in the transmission of viruses, affecting wild and domestic animals worldwide (Mellor et al 2000). African horse sickness (AHS) is one of the most important and lethal infectious diseases endemic in sub-Saharan Africa affecting equids leading to high mortality rates in susceptible horses (>90 %). Bluetongue (BT) is an important livestock disease affecting ruminants (Mehlhorn et al 2007) with a particular concern in sub-Saharan Africa for imported breeds of sheep The local sheep breeds in Senegal do not seem to express clinical signs of BT infection, seroprevalence rates remains high among sheep and goats 1983) and the importance of BT for local ruminants remains poorly understand.

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