Epidemiology and control of Menangle virus in pigs.
To describe the epidemiology and eradication of Menangle virus infection in pigs, serum samples were collected from pigs at a 2600-sow intensive piggery in New South Wales, Australia that experienced an outbreak of reproductive disease in 1997. Serum samples were also collected from piggeries that received pigs from or supplied pigs to the affected piggery and from other piggeries from Australia. Serum and tissue samples were collected from pigs at piggeries experiencing reproductive diseases in New South Wales. Sera and faeces were collected from grey-headed flying foxes (Pteropus poliocephalus) in the region of the affected piggery. Serum samples were tested for neutralizing antibodies against Menangle virus. Virus isolation was attempted from the faeces. Following the outbreak of reproductive disease, sera from 96% of adult pigs at the affected piggery, included sows that produced affected litters, contained neutralizing antibodies against Menangle virus. Neutralizing antibodies were also detected in sera from 88% of finisher pigs at 2 piggeries receiving weaned pigs from the affected piggery. No evidence of Menangle virus infection was found in other piggeries in Australia. In cross-sectional studies at the affected piggery, colostral antibodies were undetectable in most pigs by 14 to 15 weeks of age. By slaughter age or entry to the breeding herd, 95% of pigs developed high antibody titres (≥128) against Menangle virus in the virus neutralization test. Menangle virus was eradicated from the affected piggery following a program of serological testing and segregation. Neutralizing antibodies against Menangle virus were also detected in P. poliocephalus from 2 colonies in the vicinity of the affected piggery. Two piggery workers were infected with Menangle virus. There was no evidence of infection in cattle, sheep, birds, rodents, feral cats and a dog at the affected piggery.