Entomological Surveillance and Arbovirus Screening in Mosquitoes from Central Morocco: First Detection of West Nile Virus in Culex pipiens from the Marrakech-Safi Region.

PURPOSE: Surveillance of arboviral vectors and screening for probable infection is very important for the planning of vector control programs, especially in countries where these activities are just beginning. In the present study, we conducted mosquito surveillance at 26 locations predicted to be at risk (according to our recently published study using Machine learning) in the Marrakech-Safi region of central Morocco. METHODS: The field studies were conducted for six consecutive months, from April to October, in 2019 and 2021. Two different methods were used to collect adult mosquitoes, human landing catches (by mouth aspirator), and CDC miniature light traps; larvae and pupae were collected using dippers. RESULTS: A total of 1907 mosquitoes were collected, belonging to 15 species across five genera (Aedes, Culex, Culiseta, Anopheles, and Coquillettidia). Out of the 1907 mosquitoes that were sampled, 53.7% (1025/1907) were in the larval stage, 42.8% (818/1907) were adults, and the remaining 3.3% (64/1907) were pupae. Among the collected and identified adults, the females represented 96.6% and blood-fed females accounted for 55.9%. The adult mosquitoes were screened for five arboviruses: dengue virus (DENV), chikungunya virus (CHIKV), Zika virus (ZIKV), Rift Valley fever virus (RVFV), and West Nile virus (WNV) by using RT-qPCR, and a pool of Cx. pipiens from Tabia (Station 14) was positive for WNV. CONCLUSION: This is the first detection of WNV in Cx. pipiens or any other mosquito species from central Morocco. The detection of several vectors within the region suggests a risk for arboviral transmission in central Morocco and appeals for entomological vigilance and the urgent need to undertake and enhance periodic surveillance campaigns in the region.