PRRS virus [31] has been isolated from boar semen [32–40]. Specific local antibodies against non-structural viral proteins (IgA) can also be detected in semen after infection, which is correlated with the duration of PRRS virus RNA excretion in semen [41]. Quantification of PRRS virus RNA in semen has been attempted using RT- nested PCR, but the biological significance of PRRS virus RNA in semen is still to be proved [42].