Surveys of Arboviruses Vectors in Four Cities Stretching Along a Railway Transect of Burkina Faso: Risk Transmission and Insecticide Susceptibility Status of Potential Vectors

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Résumé

Background: A severe outbreak of dengue occurred in Burkina Faso in 2016, with the
most cases reported in Ouagadougou, that highlights the necessity to implement vector
surveillance system. This study aims to estimate the risk of arboviruses transmission and
the insecticide susceptibility status of potential vectors in four sites in Burkina Faso.
Methods: From June to September 2016, house-to-house cross sectional
entomological surveys were performed in four cities stretching along a
southwest-to-northeast railway transect. The household surveys analyzed the presence
of Aedes spp. larvae in containers holding water and the World Health Organization
(WHO) larval abundance indices were estimated. WHO tube assays was used to
evaluate the insecticide susceptibility within Aedes populations from these localities.
Results: A total of 31,378 mosquitoes’ larvae were collected from 1,330 containers
holding water. Aedes spp. was the most abundant (95.19%) followed by Culex spp.
(4.75%). Aedes aegypti a key vector of arboviruses (ARBOV) in West Africa was the
major Aedes species found (98.60%). The relative larval indices, house index, container
and Breteau indexes were high, up to 70, 35, and 10, respectively. Aedes aegypti
tended to breed mainly in discarded tires and terracotta jars. Except in Banfora the
western city, Ae. aegypti populations were resistant to deltamethrin 0.05% in the other
localities with low mortality rate under 20% in Ouagadougou whereas they were fully
susceptible to malathion 5% whatever the site. Intermediate resistance was observed in
the four sites with mortality rates varying between 78 and 94% with bendiocarb 0.1%.
Conclusions: This study provided basic information on entomological indices that can
help to monitor the risks of ARBOV epidemics in the main cities along the railway in
Burkina Faso. In these cities, all larval indices exceeded the risk level of ARBOV outbreak.
Aedes aegypti the main species collected was resistant to deltamethrin 0.05% and
bendiocarb 0.1% whereas they were fully susceptible to malathion 5%. The monitoring of
insecticide resistance is also important to be integrated to the vector surveillance system
in Burkina Faso.

Mots-clés

Aedes aegypti, Stegomyia indices, insecticide resistance, railway transect, Burkina Faso