First detection of the malaria vector Anopheles arabiensis Patton 1905 in Côte d’Ivoire: urbanization in question

Abstract Background: Previous studies have revealed a high malaria transmission in Bouaké, Côte d'Ivoire. The socio-political crisis in the country, and the resulting environmental changes, have raised the need to update the knowledge on mosquito vector species and malaria transmission.Methods: Adult mosquitoes were sampled using the human landing catch (HLC) sampling method in Bouaké. They were collected for 216 nights between 2019 and 2020 in six districts representative of the diversity in urban landscape. Sampling points were selected along the water network crossing the city and monitored from 2020 to 2021 to detect the presence of anopheline larvae. We used PCR techniques to ascertain the species of the Anopheles gambiae complex, Plasmodium falciparum sporozoite infection in a subset of Anopheles vectors, and insecticide resistance mechanisms in Anopheles arabiensis only.Results: A total of 4599 Anopheles mosquitoes were collected and then identified. An. gambiae s.l. was found in majority (99 %), while An. funestus, An. ziemanni, An. pharoensis were also found but in low proportions. Among the Anopheles gambiae complex, three species were identified: An. gambiae s.s. (45.9 %), An. coluzzi (52.2 %), and An. arabiensis (1.9 %). The first two species had already been collected in Bouaké, however it is the first time that An. arabiensis is reported both in Bouaké and in Côte d’Ivoire. Anopheles arabiensis was also collected during the larval surveys in a similar proportion (1.1 %) in the same areas as the adults. Conclusions: This study detected the presence of An. arabiensis in Bouaké for the first time. This species was found quite far from its usual geographic area and its expansion could be linked to the urbanization process. Though no An. arabiensis was found infected by Plasmodium sp., its role in malaria transmission in Bouaké has to be explored, particularly since its exophagic behavior raises the issue of control measures and the use of insecticide-impregnated nets. The spread of this species in Côte d'Ivoire should be assessed through further research in additional towns in the country.