Abstract:
West Nile virus (WNV) and Usutu virus (USUV) are members of the family Flaviviridae
which, natural life cycles involve mosquito–bird–mosquito transmission. Both represent emerging
viruses in Europe with potential to cause neuroinvasive disease in humans. This study investigates
the seroprevalence of serum neutralizing antibodies to WNV and to USUV in birds and in horses in
Poland. Antibodies against WNV and USUV were detected in 5 (35.7%) and in 1 (7.14%) of 14 birds
and in 62 (15.08%) and in 115 (27.98%) of 411 horses, respectively. Twenty-one WNV serologically
positive horses (33.87%) and 67 USUV serologically positive horses (58.26%) did not travel outside
Polish borders. Given the high abundance of potentially competent mosquito species in Poland,
high populations of horses and different bird species, our findings highlight implementation of active
control programs, including monitoring of geographic spread and dynamics of WNV and USUV
transmission in both primary and accidental hosts. It is also important to improve public health
awareness about the disease these viruses may cause.
