Detection of classical swine fever virus in semen of infected boars.

During the Classical Swine Fever (CSF) epidemic in 1997 in the EU member states Germany, Italy, Spain and The Netherlands, boars in an artificial insemination (AI) centre were found to be infected with CSF virus. This raised a question of epidemiological importance which could not be answered immediately. Can CSF virus be shed by semen of infected boars and what conclusions concerning the risk of spreading CSF infection by semen can be drawn. Experimental studies were conducted to answer this question. Four young boars were infected with a CSF field virus isolate from Germany, which had been characterised in a previous animal experiment. Semen was collected at least every other day after infection. The semen was subjected to the standard diagnostic procedure for the detection of CSF virus and to semen quality assessment. The boars were euthanized at day 8, 12, 16 and 21 post infection, respectively. A post mortem examination was done and organ samples were taken from the CSF reference organs and genital organs for the detection of virus and antigen. The course of CSF infection of the boars was mild but detectable during the second week of infection. CSF virus could be isolated from semen of two animals during the pyrexic phase and from the epididymis but not from the testes. Since CSF virus shedding via semen could be proven, it was concluded that the disease may also be transmitted by artificial insemination. However analysis of semen in cell culture for the presence of CSF virus is not suitable as a routine method for CSF diagnosis.