Detection of antibodies against classical swine fever virus in fecal samples from wild boar

Classical swine fever (CSF) is a contagious viral disease that affects pigs. Wild boars can play an important epidemiological role in CSF outbreaks. In the past decades, studies conducted in many countries have reported that the CSF virus (CSFV) may persist in wild boar populations. The existence of CSFV in the free-ranging wild boar populations was indirectly confirmed by determining the prevalence of antibodies against CSFV in the serum of hunted wild boars. However, analyzing sero-prevalence in hunted wild boars to study the risk of CSF outbreaks is difficult due to insufficient number of samples, limitation of hunting area and biased age distribution of hunted wild boars. To improve this survey method, we collected feces of wild boars from their habitat and tested them using CSFV antibody enzyme-linked immunosorbent assay (ELISA) and CSF virus neutralization (VN) test. In this study, ELISA was found to be highly sensitive for detecting antibodies against CSFV in fecal samples. Most of doubtful or positive results obtained in CSFV ELISA were confirmed by VN tests. Despite the high coincidence rate of antibody-positive samples between CSFV ELISA and VN test, the possibility of false positive reaction should be considered. In the regional distribution, a fact that antibody-positive fecal and serum samples were found in geographically close area was shown. Hence, presence of antibodies in fecal samples may provide vital information regarding the risk of CSF outbreaks in wild boar groups in geographical proximity.