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An epizootic of encephalomyocarditis virus (EMCV) disease in pigs in the central west of New South Wales in association with a plague of mice (Mus musculus) in 1984 is described. The disease was confirmed in 47 outbreaks in 37 piggeries and 1152 pigs died, representing an overall death rate of 17.4% in pigs considered at risk. The disease was diagnosed in both intensively housed pigs and pigs farmed outdoors, with mortality rates higher in piggeries with less than 50 sows. The age at which pigs died ranged from 4 days to 24 weeks with higher death rates in younger pigs. Serological testing of pigs slaughtered at Blayney abattoir indicated EMCV infection to be more widespread than the disease reported. Mice were present in all piggeries reporting the disease while rats were present in 66% of the outbreaks. The role of rodents as natural reservoirs of EMCV and the possibility of variations in pathogenicity amongst strains of the virus are discussed.

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A syndrome in cattle of diarrhoea and death associated with enteric Yersinia pseudotuberculosis infection is described. Outbreaks occurred during winter and early spring in adult cattle grazing pastures waterlogged by recent flooding or persistent heavy rain. Antibiotic therapy was effective early in the course of the syndrome. At necropsy there was severe acute enterocolitis, and bacteria consistent with Y. pseudotuberculosis were observed in the lesions. This organism could usually be isolated from the intestines of affected animals but was recovered less often from other organs. Representative isolates were identified as Y. pseudotuberculosis serotype III. The association of this syndrome with waterlogged pastures and low temperatures suggests that these conditions favour transmission of Y. pseudotuberculosis infection in cattle. The role of Y. pseudotuberculosis as primary pathogen requires confirmation.