West Nile, Sindbis and Usutu Viruses: Evidence of Circulation in Mosquitoes and Horses in Tunisia

Abstract

Mosquito-borne diseases have a significant impact on humans and animals and this impact is exacerbated by environmental changes. However, in Tunisia, surveillance of the West Nile virus (WNV) is based solely on the surveillance of human neuroinvasive infections and no study has reported mosquito-borne viruses (MBVs), nor has there been any thorough serological investigation of anti-MBV antibodies in horses. This study therefore sought to investigate the presence of MBVs in Tunisia. Among tested mosquito pools, infections by WNV, Usutu virus (USUV), and Sindbis virus (SINV) were identified in Cx. perexiguus. The serosurvey showed that 146 of 369 surveyed horses were positive for flavivirus antibodies using the cELISA test. The microsphere immunoassay (MIA) showed that 74 of 104 flavivirus cELISA-positive horses were positive for WNV, 8 were positive for USUV, 7 were positive for undetermined flaviviruses, and 2 were positive for tick-borne encephalitis virus (TBEV). Virus neutralization tests and MIA results correlated well. This study is the first to report the detection of WNV, USUV and SINV in Cx. perexiguus in Tunisia. Besides, it has shown that there is a significant circulation of WNV and USUV among horses, which is likely to cause future sporadic outbreaks. An integrated arbovirus surveillance system that includes entomological surveillance as an early alert system is of major epidemiological importance.

Evidence of West Nile Virus Circulation in Horses and Dogs in Libya

“…Due to the lack of availability of epidemiological data on WND in Libya, the expected prevalence was based on published information from regional and neighbouring countries [9,[28][29][30][31]. The proximate of the prevalence was 30% with CI 95%.…”

A metagenomics-based survey of the virus diversity in mosquito vectors allows the first detection of Sindbis virus in Burkina Faso

“…However, the geographical source of European strains remains to be further explored because SINV sequences are only available from a limited number of African regions. Moreover, recent reports suggest that SINV is either spreading into new African regions or endemic in a larger area than previously thought [29,30]. Thus, the paucity of data on SINV hampers to fully evaluate its distribution in Africa and routes of spread.…”

Relevance of the synergy of surveillance and populational networks in understanding the Usutu virus outbreak within common blackbirds (Turdus merula) in Metropolitan France, 2018

“…The Usutu virus (USUV), so called because of its isolation in Culex neavei mosquitoes in 1959 (McIntosh 1985) near the Usutu river in Swaziland (Eswatini since 2018) is an arbovirus of the Flaviviridae family, Orthoflavivirus genus (Clé et al 2019), belonging to the Japanese encephalitis virus serocomplex, and phylogenetically close to Japanese Encephalitis Virus (JEV) and West Nile Virus (WNV) (Calisher and Gould 2003). After South Africa, the virus was detected in other African countries: Central African Republic, Senegal, Ivory Coast, Nigeria (Nikolay et al 2011), Uganda (Nikolay et al 2011;Mossel et al 2017), Burkina Faso (Nikolay et al 2011), Mali, Madagascar (Chevalier et al 2020), Kenya (Ochieng et al 2013), Tunisia (Ben Hassine et al 2014;M'ghirbi et al 2023), Morocco (Durand et al 2016), and Israel (Mannasse et al 2017). The first known occurrence in Europe dates back to 1996 in Italy (a retrospective finding in dead birds, mainly blackbirds) (Weissenböck et al 2013).…”