Reproductive disease and congenital malformations caused by Menangle virus in pigs.
To describe a new syndrome characterized by embryonic mortalities, stillbirths, mummified fetuses and congenital malformations in a herd of intensively farmed pigs, pathology examinations were performed on mummified fetuses and congenital deformed piglets during an outbreak of reproductive diseases at a 2600 sow intensive piggery in New South Wales, Australia from April to October 1997. Reproductive performance was monitored during the outbreak and breeding records were examined retrospectively. Serum and tissue samples from pigs were tested for evidence of infection with known porcine pathogens and for a new virus, Menangle virus, isolated from stillborn piglets with deformities from the affected piggery in August 1997. Reproductive disease occurred sequentially in all 4 breeding units at the affected piggery over a period of 21 weeks. The farrowing percentages in each unit decreased from 80 to 82% before the outbreak to 63 to 78% during the outbreak and the number of live piglets per litter declined from a mean of 9.6 to 9.8 before the outbreak to 7.2 to 8.9 during the outbreak. The proportion of affected litters (litters with <6 liveborn piglets) was highest (64%) in the 6th week of the outbreak. Mummified fetuses, stillborn piglets with arthrogryposis, craniofacial deformities and degeneration of the brain and spinal cord, were observed along with occasional abortions. Sera from sows that produced affected litters contained neutralizing antibodies against Menangle virus and there was evidence that this virus had been introduced to the piggery in February 1997.