Infections with Yersinia pseudotuberculosis serotype III and Y. enterocolitica serotype 02,3 were found to be common in Australian sheep flocks. Transmission of Y. pseudotuberculosis occurred in late winter and early spring, while Y. enterocolitica transmission occurred from midwinter to early summer. Excretion of Y. pseudotuberculosis was limited to the winter and spring period and was particularly common in 1and 2-year-old sheep. Infection persisted for up to 14 weeks. Y. pseudotuberculosis infection did not confer immunity to natural infection with Y. enterocolitica. Y. enterocolitica excretion occurred year-round, with the greatest prevalence being in summer and autumn. Infection persisted for up to 29 weeks. Sheep less than 1 year old were most commonly infected with Y. enterocolitica. Infection with either Y. pseudotuberculosis or Y. enterocolitica was rare in aged sheep. Restriction endonuclease analysis of Y. pseudotuberculosis serotype III from sheep, cattle, deer, and pigs showed that the bacterial isolates were genetically indistinguishable. Similarly, Y. enterocolitica isolates from sheep were indistinguishable from those isolated from goats and cattle. The Gippsland region of Victoria, Australia, is a major sheepand cattle-raising area. Livestock graze on pasture for 12 months of the year, and housing is not necessary. Winters are mild, and summers are warm, with most of the rain falling in winter and spring. Sheep in the study area are raised for both meat and wool production. Merino and British breeds and their crosses are all present. The number of sheep on a farm varies, but a range of several hundred to several thousand animals is usual. Cattle are often grazed with sheep. Sheep on farms are normally allocated into groups based on gender and age class and are managed as separate flocks.

Kidneys from cattle at slaughter were examined for the presence of leptospires. Of 218 (8.3%) kidneys leptospires were isolated from 18; all were identified as Leptospira interrogans serovar hardjo. None of the leptospire-infected kidneys had histopathological lesions indicative of leptospirosis and leptospires were demonstrated in only 2 by immunogold silver staining. Leptospires infected kidneys remained viable for at least 21 days when stored at 4 degrees but became non-viable within 14 days when stored frozen at -15 degrees.

The aim of this study was to determine whether evidence could be obtained of foetal infection with Leptospira interrogans serovar hardjo in aborted foetuses collected from dairy farms. Material from 197 abortions occurring over a wide area of Victoria was collected over 3 years. None of 195 foetal kidney cultures or 7 cultures from membranes was positive for leptospiral organisms. Immunogold silver staining for leptospires was performed on sections of kidneys, lungs or heart from 156 foetuses, with negative results. Evidence of transient leptospiral infection in 11 of 123 foetuses was obtained by foetal heart blood serology. Two isolates of L. interrogans serovar hardjo were obtained from the urine of milking cows. These strains were examined by restriction endonuclease analysis and both were shown to be of the genotype Hardjobovis, as have been all Australian isolates studied so far. It appears that foetal infection with serovar hardjo is not associated with any substantial proportion of bovine abortions in Victoria, in contrast to the situation in Northern Ireland. The apparent absence from Victoria of the pathogenic genotype Hardjoprajitno is a possible explanation.

Of several media tested for their ability to induce asexual reproduction in confirmed or suspected isolates of Mortierella wolfii obtained from cattle in various geographical locations, only silage extract agar worked consistently and rapidly. Its use should provide a simple reliable culturing procedure to assist with identification of clinical isolates of this fungus. Temperature growth response curves and electrophoretic patterns of soluble protein extracts of these isolates with characteristic morphological features of M. wolfii indicate substantial variation amongst them.Mortierella wolfii, Mehrotra and Baijal has been identified in aborting cattle in Britain [11] and in New Zealand [4] and Australia [9], where this fungus is considered to be one of the most important causes of systemic mycosis in cattle. However its incidence is probably underestimated. Many cases have remained undiagnosed because, although M. wolfii infection was suspected, it was not often identified with certainty. Even if the aborted placental tissue can be located for examination, the infecting hyphae are not distinctive enough to allow an unequivocal histological diagnosis [5]. Several serological procedures have been tried in attempts to recognize infected cattle, but with varying degrees of success [11,16]. Attempts to culture isolates and identify them on their reproductive morphology have been frustrated by the inability of many isolates to sporulate in culture on media such as potato glucose, Sabouraud or blood agar [6]. Therefore in many cases, M. wolfii has been tentatively identified mainly on the basis of the distinctive nature of the colonies, having the appearance of rosettes of overlapping lobes on some media [7].In this study, attempts were made to find a medium promoting sporulation in isolates of M. wolfii which could then be used to assist with positive identification.Polyacrylamide gel electrophoresis (PAGE) of mycelial proteins was also investigated as an alternative means of identifying isolates which would not sporulate in culture, but which would grow vegetatively.

During 1981, 265 bovine abortions were investigated by serological and histological methods for evidence of leptospiral infection. Leptospires were demonstrated in the tissues of 10 foetuses by a Levaditi silver impregnation technique. Serological testing of maternal sera indicated that Leptospira interrogans serovar hardjo was associated with 5 of the abortions while the remaining 5 were due to L. interrogans serovar pomona infection. In cases of abortion associated with L. interrogans serovar hardjo leptospires were readily demonstrated in foetal liver, kidney, intestine and heart. They were demonstrated less often in lung and placenta and could not be found in foetal brain. Autolysis did not appear to interfere with the demonstration of leptospires by silver impregnation. No lesions attributable to leptospiral infection were seen in placentas but mild interstitial nephritis was found in some of the foetuses. Fourteen other cows had serological evidence of recent leptospiral infection but leptospires were not detected in foetal tissues. Histological examination of silver impregnated foetal tissues in combination with the microscopic agglutination test was shown to be an effective method for diagnosing abortion associated with L. interrogans serovar hardjo in cattle.