Abstract
The surveillance for West Nile virus (WNV) in Catalonia (northeastern Spain) has consistently detected flaviviruses not identified as WNV. With the aim of characterizing the flaviviruses circulating in Catalonia, serum samples from birds and horses collected between 2010 and 2019 and positive by panflavivirus competition ELISA (cELISA) were analyzed by microneutralization test (MNT) against different flaviviruses. A third of the samples tested were inconclusive by MNT, highlighting the limitations of current diagnostic techniques. Our results evidenced the widespread circulation of flaviviruses, in particular WNV, but also Usutu virus (USUV), and suggest that chicken and horses could serve as sentinels for both viruses. In several regions, WNV and USUV overlapped, but no significant geographical aggregation was observed. Bagaza virus (BAGV) was not detected in birds, while positivity to tick-borne encephalitis virus (TBEV) was sporadically detected in horses although no endemic foci were observed. So far, no human infections by WNV, USUV, or TBEV have been reported in Catalonia. However, these zoonotic flaviviruses need to be kept under surveillance, ideally within a One Health framework.
Highlights
The genus Flavivirus includes important human zoonotic pathogens such as dengue virus (DENV), yellow fever virus (YFV), West Nile virus (WNV), tick-borne encephalitis virus (TBEV), and Japanese encephalitis virus (JEV)
Of 3791 serum samples collected from birds between 2010 and 2019 in Catalonia within the WNV Surveillance Program, 380 tested positive by panflavivirus competition ELISA (cELISA) (IDvet), and of them, 205 had enough serum to be tested by micro-neutralization test (MNT) at the CISA
To measure neutralizing antibody responses against different flaviviruses, microneutralization test (MNT) were performed in parallel against WNV, USUV (SAAR-1776), and Bagaza virus (BAGV)
Summary
The genus Flavivirus includes important human zoonotic pathogens such as dengue virus (DENV), yellow fever virus (YFV), West Nile virus (WNV), tick-borne encephalitis virus (TBEV), and Japanese encephalitis virus (JEV). Usutu virus (USUV) and Bagaza virus (BAGV), can cause severe disease in animals. They are arboviruses, and are transmitted from an infectious to a susceptible vertebrate host via hematophagous arthropod vectors, such as mosquitoes or ticks. WNV, USUV, or TBEV have significantly increased [1]. Many of these viruses are currently endemic in several areas of the continent. Expansion and endemicity increase spatial and temporal overlapping of flaviviruses in Europe, which in turn poses significant challenges for surveillance and control [2]. Given the trends in climate warming and land-use changes, as well as the increase of human travel and the intensification of the trade of animals and goods, the situation is likely to become even more complex in the future [3]
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