Flaviviruses in migratory passerines during spring stopover in a desert oasis

Abstract

Bird migration has long been hypothesized as the main mechanism for long‐distance dispersal of flaviviruses, but the role of migratory birds in flaviviruses spillover is not well documented. In this study, we investigated the eco‐epidemiology of West Nile virus (WNV) and Usutu virus (USUV) in trans‐Saharan passerines during their spring stopover in southern Tunisian oases. To do, we combined oral swab analysis and serological tools to assess whether migratory birds could be reaching these stopover sites while infectious or have been previously exposed to viruses. All sampled birds tested negative for oral swab analysis. However, anti‐WNV and anti‐USUV antibodies were detected in 32% and 1% of tested birds, respectively. Among WNV‐seropositive species, the Golden oriole (Oriolus oriolus) showed the highest anti‐WNV occurrence probability. In this species, anti‐WNV occurrence was twice larger in males than females. Inter‐specific and intraspecific morphological, physiological and behavioural differences could explain these results. Although our findings did not show evidence for passerines migrating while infectious, they did not exclude an existing enzootic WNV transmission cycle in Tunisian oases. Further investigations including larger samples of migratory birds are needed for a better understanding of this issue.

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

“…This high rate of WNV seroprevalence has also been reported by other team in Tunises and Algeria (Ben Hassine et al, 2014;Lafri et al, 2017). USUV and WNV have been shown to co circulate and share the same vectors (Zannoli and Sambri, 2019); however, we did not detect USUV either in mosquitoes nor in horse sera, while USUV has been shown to circulate in Tunisia and in Morocco (Ayadi et al, 2019;Ben Hassine et al, 2014;Figuerola et al, 2009).…”

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

“…It corroborated previous results, where infection rates were highest in regions with WNV outbreaks, including in the north-eastern governorates (Jendouba, 74%), the eastern coast (Monastir, 64%) and the lowlands of Chott El Jerid and Chott el Gharsa (Kebili, 58%, Tozeur, 52%) [ 79 ]. In addition, anti-WNV and anti-USUV antibodies were detected in 32% and 1% respectively of tested birds in Tunisian oases [ 80 ].…”

“…This high rate of WNV seroprevalence was also reported in Algeria [ 36 , 96 ]. USUV and WNV have been shown to co-circulate and share the same vector species but no single infection by USUV was detected in mosquitoes, although it was shown to circulate previously in Tunisia and in Morocco [ 36 , 80 ]. Despite USUV RNA detection, further studies are needed to assess the status of USUV in RBP as it was not amplified by PCR.…”

Transboundary determinants of avian zoonotic infectious diseases: challenges for strengthening research capacity and connecting surveillance networks

“…Migratory birds play a crucial role in the transmission of infectious diseases, serving as both hosts and vectors for various pathogens. The intercontinental movement of wild birds across vast geographical areas can provide opportunities for the exchange of pathogens between different regions and populations (e.g., Dusek et al, 2009;Araujo et al, 2018;Ayadi et al, 2019). The best known, and most documented example, is the H5N1 avian influenza virus that has been detected in wild birds during migration, contributing to the global dissemination of the virus (Olsen et al, 2006).…”