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Serological test results for leptospiral species on serums from cattle and pigs performed by the diagnostic laboratories of the Queensland Department of Primary Industries from July 1973 to June 1976 were used to determine the prevalence and geographical distribution of 3 leptospiral serotypes in Queensland. There was a higher prevalence of antibodies to L. hardjo than to L. pomona in cattle, whereas in pigs the prevalence of antibodies to L. pomona was much higher than that for L. tarassovi or L. hardjo. Feral pigs had a particularly high prevalence of L. pomona antibodies. There is a different geographical distribution of antibodies to L. pomona and L. hardjo. L. hardjo antibodies appear to be fairly uniformly distributed but there is a higher prevalence of L. pomona antibodies in low rainfall areas. This relationship was shown to be significantly correlated.

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To investigate relationships between serological titres to 2 serovars, pomona (L. pomona) and hardjo (L. hardjo), of Leptospira interrogans and abortions, log linear and logit models were fitted to herd and individual cow data from cattle serologically negative for brucellosis. Serological titres to both serovars were significantly related to abortions in individual cows, with L. pomona having a stronger relationship than L. hardjo. L. hardjo was not significant when herd data were analysed. Differences between dairy and beef cattle in the serological titres found to both L. pomona and L. hardjo were detected when data sets of all cattle or cattle with no history of abortion were analysed. The beef/dairy differences may be due to different management practices and/or to different geographical distributions of both serovars and populations of beef and dairy cattle. If there are no cattle in a herd with a reciprocal titre of 3000 or greater for L. pomona, it is unlikely that L. pomona is associated with the abortion problem. There was no specific L. hardjo titre which separated high and low probabilities that the serum came from a cow or herd with an abortion history.

Summary Serological examination of 177 strains of haemolytic Escherichia coil from pigs from 95 piggeries showed that 50 isolates from 28 piggeries were agglutinated by serums prepared against 0141:K85ab, 45 from 20 piggeries by 0141:K85ac, 32 isolates from 19 piggeries by 08 and four isolates from two piggeries by 0139:K82. Forty‐six strains from 26 piggeries were unclassified. Ninety strains were isolated from intestine and/or mesenteric lymph nodes and 87 from other organs. Of the 95 outbreaks associated with haemolytic E. coli, 41 were diagnosed as oedema disease, 40 as coli‐enteritis and the remainder were miscellaneous conditions. The clinical and pathological features of outbreaks associated with colibacillosis and septicaemic salmonellosis were compared and discussed.