Reproductive disease and congenital malformations caused by Menangle virus in pigs.

OBJECTIVE

To describe a new syndrome characterised by embryonic mortalities, stillbirths, mummified foetuses and congenital malformations in a herd of intensively farmed pigs.

DESIGN

Field observations, laboratory investigations and examination of breeding records.

PROCEDURE

Pathology examinations were performed on mummified and congenitally deformed piglets during an outbreak of reproductive disease at a 2600 sow intensive piggery in New South Wales 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.

RESULTS

Reproductive disease occurred sequentially in all four 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 less than six liveborn piglets) was highest (64%) in the sixth week of the outbreak. Mummified foetuses, 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 neutralising antibodies against Menangle virus and there was evidence that this virus had been introduced to the piggery in February 1997.

CONCLUSIONS

Reproductive disease in pigs due to Menangle virus was characterised by stillbirths, mummification, embryonic death and infertility, along with abortions, skeletal deformities and degeneration of the brain and spinal cord in affected foetuses and stillborn piglets.