Five outbreaks of myocarditis were investigated in young sheep. They occurred during late winter and spring when there was lush growth of pasture following a prolonged period of drought. Clinically the disease was characterised by sudden death and pathological findings were dominated by acute multifocal locally extensive necrotising and haemorrhagic myocarditis. A fluorescent antibody technique was used to demonstrate the presence of Clostridium chauvoei in paraffin embedded sections of myocardium from 4 of the outbreaks.

Cerebral microangiopathy is described in naturally occurring clostridial enterotoxaemia in two goats. The two cases were selected from the files of two diagnostic laboratories in Australia, on the basis that the clinical syndrome and history were consistent with a diagnosis of enterotoxaemia, and that the diagnosis was confirmed by the identification of epsilon toxin in the intestinal contents. The lesions consisted of acute perivascular proteinaceous exudate in the brain and bilaterally symmetrical foci of encephalomalacia were observed in one of the goats. These brain lesions confirm that Clostridium perfringens type D enterotoxaemia may produce histologically detectable brain changes in goats.

Histophilus ovis was isolated from 29 sheep in 20 flocks and 2 artificial insemination (AI) centres in southern New South Wales from 1984 to 1990. The clinical and pathological findings were consistent with previous reports and included polyarthritis (7 flocks), epididymo-orchitis (5), meningoencephalitis (3), pneumonia (3), septicaemia (2), mastitis (1) and metritis (1). Six sheep had meningoencephalitis, a syndrome not previously associated with H ovis infection in sheep, which was similar pathologically to thromboembolic meningoencephalitis in cattle, caused by the related organism, Haemophilus somnus. H ovis was isolated from the semen of 12-month-old rams in a flock that had polyarthritis due to H ovis, in 4-month-old ram lambs and from the uterus of a ewe in a flock that had sporadic cases of H ovis septicaemia.

In 40 submissions to the Regional Veterinary Laboratory (RVL) Wagga Wagga from sheep in southern New South Wales from 1981 to 1989, 53 isolates of Yersinia sp were recovered from 45 sheep in 37 flocks. Of 53 isolates, 26 were identified as Y. pseudotuberculosis, 20 as Y. enterocolitica, 5 as Y. intermedia and 2 as Y. frederiksenii. Twelve isolates of Y. pseudotuberculosis tested in the slide agglutination test all belonged to serotype III. The 20 Y. enterocolitica isolates were categorised biochemically as biotype 5 strains and, of 6 isolates serotyped, all belonged to serogroup 2,3. Outbreaks of yersiniosis were most common in late winter and early spring and affected flocks often had experienced a change in husbandry. Infection with Yersinia sp was associated with diarrhoea, illthrift and mortality. At necropsy, congestion and occasionally thickening of the intestinal mucosa were observed in affected sheep. Gastrointestinal nematodiasis and coccidiosis often were concurrent findings. The characteristic histological lesion in sheep infected with Y. pseudotuberculosis was acute segmental suppurative erosive enterocolitis. There were no lesions consistently associated with Y. enterocolitica, Y. intermedia or Y. frederiksenii.

Preweaning mortality was studied in 34 commercial piggeries on the North Coast of New South Wales during a 12-month period. For the 1,068 farrowings recorded, the mean litter size at birth was 10.4 and 0.6 piglets per litter were stillborn. The mean total mortality to weaning was 19.7%, but for individual herds the figure varied from 5.1 to 48.2%. A number of biological factors influenced the extent of preweaning mortality. Most losses (74.6%) occurred during the first 4 days of life. The mortality increased significantly with increasing litter size at birth, but the mean litter size at weaning also increased up to 10.5 in litters of originial size 14. Neither the breed nor parity of the sow had a significant effect on preweaning mortality, but the mean number of piglets weaned increased with parity up to sows on their fifth farrowing. Some management factors also influenced mortality. Piggeries using farrowing crates had significantly fewer losses than those not using crates. Within the group not using crates the intensive units had a higher preweaning mortality than either the mixed or sideline. Size of piggery had no influence on piglet losses.