Identification of seropositive wild boars in Eurasia as a sign of possible formation of African swine fever-endemic areas (review)

Abstract

The continued spread of African swine fever (ASF) in Eurasia remains a global problem for the world pig industry. The disease is characterized by high mortality (up to 100 %) and acute course - domestic and wild animals die within the first two weeks after infection. However, active surveillance on ASF in Eastern Europe had been showing regular detection of seropositive susceptible animals, especially among wild boar populations which may indicate chronic, asymptomatic infection and even the survival of individual animals. At the same time, the persistence of the virus in the wild boar population creates constant risks of sporadic outbreaks of ASF in infected areas, and the infection can become endemic. The aim of the study was a systematic review of the available data on seroprevalence among wild boars in relation to the possible establishment of ASF endemicity in Eurasia. In these animals, there was a change in the dynamics of the disease, which is manifested by self-sustaining cycles of infection. Seropositive wild boars are being found in the Baltic countries, Hungary, Poland, Romania, Slovakia, and Russia. Seroprevalence rates among wild boars hunted in ASF-infected areas of European countries range from 0.3 to 3.8 %. In the Baltic countries, the number of seropositive samples from wild boars exceeds the number of samples positive for ASF virus in polymer chain reaction (PCR). A similar trend persists in those regions where the ASF virus has been present for a long time (Poland, Lithuania, Latvia, Estonia), which may indicate the endemic nature of ASF. In the Russian Federation, ASF-endemic territories in the wild have not yet been registered, although isolated cases of seropositive wild boars have been detected in some regions since 2013. In the future, in order to understand the dynamics of the disease in the wild, it is necessary to conduct a comprehensive diagnosis of the ASF virus genome and antibodies in wild boar samples, which eventually will allow choosing the right strategy to combat ASF.