Semens role in spread questioned
THERE is strong circumstantial evidence that porcine circovirus type 2 (PCV-2) has entered closed pig units via semen, which East Anglia-based vet Roger Harvey believes has caused PDNS and PMWS on units previously free from both diseases.
"Foot-and-mouth and classical swine fever restrictions have forced producers to obtain semen from alternative sources," he told the seminar. "The herds involved were fully closed to live animals and semen was the only possible route."
Mr Harveys views met a mixed reaction. He gained support from French vet Jean-Michel Guillaume, but VLAs Andrew Gresham said semen was not a major risk factor.
"PCV-2 has been detected in semen, but the question is whether virus is viable," said Mr Gresham.
Research has failed to detect viable virus in semen, according to Gordon Allan, researcher at the Northern Ireland Vet Sciences Division. "If it was, how would you treat semen to kill the virus while maintaining semen viability?" *
PCV-2 is more difficult to kill than the F&M virus and is the smallest virus known to affect mammals, said Dr Allan. There are few disinfectants which are known to be effective against it. *