Evidence of circulation of West Nile virus in Culex pipiens mosquitoes and horses in Morocco

Abstract

West Nile virus (WNV) is one of the most widely distributed mosquito-borne viruses in the world. In North Africa, it causes human cases of meningoencephalitis with fatalities in Algeria and in Tunisia, whereas only horses were affected in Morocco. The aims of this study were to detect WNV in mosquitoes and to determine seroprevalence of WNV in Moroccan horses by the detection of IgG antibodies. A total of 1,455 mosquitoes belonging to four different species were grouped by collection site, date, and sex with 10 specimens per pool and tested for 38 arboviruses using a high-throughput chip based on the BioMark Dynamic array system. Out of 146 mosquito pools tested, one pool was positive for WNV. This positive pool was confirmed by real time RT-PCR. The serosurvey showed that 33.7% (31/92) of horses were positive for competitive enzyme-linked immunosorbent assay (cELISA) test. The flavivirus-sphere microsphere immnoassay (MIA) test, targeting three flaviviruses (WNV, Usutu virus (USUV) and Tick borne encephalitic virus (TBEV)) showed that 23 sera out of 31 were positive for WNV, two for USUV, two for USUV or WNV, and four for an undetermined flavivirus. Virus neutralization tests with USUV and WNV showed that 28 of 31 sera were positive for WNV and all sera were negative for USUV. This study reports, for the first time, the detection of WNV from Culex pipiens mosquitoes in Morocco and its circulation among horses. This highlights that the detection of arboviruses in mosquitoes could serve as an early warning signal of a viral activity to prevent future outbreaks in animals and humans.

Distribution of insecticide resistance and molecular mechanisms involved in the West Nile vector Culex pipiens in Morocco

“…More worryingly, the fact that OP and PYR resistances are already quite prevalent all over Morocco could impede mosquito control, while alternative insecticides are very limited. Beyond the nuisance and its impact on tourism, control failures could in this country lead to increased arbovirus transmission, as the WNV is actively circulating in Morocco, 58 which increases the risk of epizootics and epidemics. This risk is further increased by the prevalence of resistance, as a study recently showed that resistance alleles tend to increase Cx.…”

A Scoping Review of West Nile Virus Seroprevalence Studies among African Equids

“…All equids of volunteer owners were sampled in Northwest Senegal and every horse available without WNV vaccination was sampled in Southwestern Nigeria. Two recent studies conducted a survey of vectors alongside the seroprevalence of WNV in equids [ 26 , 40 ].…”

“…Neutralization tests can resolve discrepancies that often occur with other assays due to cross-reactivity. Confirmatory neutralization tests were performed in most studies after initial screening with ELISA, microsphere immunoassay [ 26 ] or Western blot [ 31 ]. Neutralization tests performed included MNT, VNT and PRNT.…”

“…Not paying attention to the cross-reactivity of flaviviruses among African equids could result in an erroneous representation of the seroprevalence of the disease. For instance, equids positive for USUV, USUV and WNV and undetermined flavivirus based on MIA were all confirmed as WNV positive by virus neutralization test [ 26 ]. On the other hand, one of the studies showed that seroprevalence determined by neutralization test varied only slightly from that determined by ELISA (30.4% vs. 33.7%, respectively) among equids in Morocco [ 26 ].…”

Comparative Genomics Analysis Demonstrated a Link Between Staphylococci Isolated From Different Sources: A Possible Public Health Risk

“…This suggests that mosquitoes could be possible vectors for transmitting S. hominis while feeding on their host and that genetically these mecA + S. hominis isolates recovered from general public settings have not evolved much since ancient times (Hughes et al, 2016). Mosquitoes are vectors for viruses, protozoa and parasites that can spread and cause disease in humans and animals but currently, it is unreported if they can transfer and initiate bacterial infections (Torres-Guerrero et al, 2017;Assaid et al, 2020;Multini et al, 2020). The ENA isolates recovered from mosquitoes (As1, As2 and As3) were genetically related to an ENA isolate recovered from healthy human skin (UMB0272) (Figure 6).…”