Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) infection in wild boars

The Porcine Reproductive and Respiratory Syndrome (PRRS) is one of the economically most important swine diseases worldwide. The virus can be spread by viraemic and persistent infected pigs. Spread and infection are advanced in areas with high herd and population densities. As wild boars have been found seropositive for PRRSV in Germany, France, and the USA, exchange between wild and domestic pig populations may exist. However, comprehensive information on PRRSV infection in wild boars is presently not available. The aim of the current study was thus, to systematically study PRRSV infection in wild boars to provide information on spatiotemporal, host and viral effects. The study was based on 531 wild boars from 52 hunts in Germany (2004-2007). PRRSV infection was determined and strains (US/EU) were classified by PCR. A total of 15.9% of the wild boars were PRRSV-positive (US: 14.2%; EU: 6.2%), with remarkable effects of state (US: 5.1-46.2%; EU: 0-17.6%), season (0-36.5%) and tissue (lungs: 89%; tonsils: 11%). Prevalences did neither correlate with age or weight, nor with density of production units, domestic pigs or wild boars. Open reading frame (ORF) 1-sequences within EU- and US-strains did not differ among wild boar samples. Homologies between EU-samples/Lelystad-virus and US-samples/PRRSV-MLV virus were 99.3 and 97%, respectively. This is the first comprehensive evidence of PRRSV infection in wild boars. We conclude that there is only a weak relation between wild boar and domestic PRRSV infection.