Primary, congenital neuroaxonal dystrophy with peripheral nerve demyelination in Merino-Border Leicester × Polled Dorset lambs.

CASE REPORT: Clinicopathological features of neuroaxonal dystrophy (NAD) in newborn, Merino-Border Leicester × Polled Dorset lambs are described. The affected lambs were unable to walk at birth and microscopic examination of brainstem and spinal cord sections revealed bilaterally symmetrical accumulations of axonal swellings (spheroids), the histological hallmark of primary NAD. The neurological deficit was also exacerbated by myelin loss and secondary axonal degeneration, particularly in the spinal cord and sciatic nerves, but also, to a more limited extent, in brainstem and spinal nerves. CONCLUSIONS: Although lambs previously diagnosed with NAD have ranged in age from 2 days to 7 months, this is believed to be the first report of congenital NAD in this species. Moreover, the present cases are the only ones in which peripheral nerve demyelination has been found.

Lythrum hyssopifolia (lesser loosestrife) poisoning of sheep in Victoria.

OBJECTIVE: To document an ovine disease attributed to the consumption of Lythrum hyssopifolia (lesser loosestrife). PROCEDURES: Historical and histological review of field and experimental cases. RESULTS: 1-20% mortality occurred in sheep flocks grazing paddocks where L. hyssopifolia was the predominant green vegetation. Well-documented disease outbreaks occurred in summer on nine farms across Victoria between 1974 and 2002. Liver damage occurred in all nine outbreaks, with kidney damage in at least eight. Hepatocyte necrosis was usually zonal to midzonal (zone 2) in the liver samples from four farms and periacinar (zone 3) in those from three farms, but some livers showed only single-cell necrosis. Multinucleate hepatocytes near necrotic areas were a feature in six cases. Proximal tubular epithelium appeared to be the primary renal target and brown granules were often present in renal tubules. Biochemical and histological evidence of liver and kidney damage was obtained from two sheep experimentally pen-fed harvested L. hyssopifolia. CONCLUSION: Chemicals in L. hyssopifolia are toxic to ovine hepatocytes and renal tubular epithelial cells.

Johne's disease in alpacas (Lama pacos) in Australia.

Johne's disease was diagnosed in 10 alpacas (Lama pacos) in Australia between February 1993 and May 1994. Eight of the animals were between 12 and 24 months of age, one was a 6-year-old female, and one was a 4-year-old male. Five, including the 6-year-old and the 4-year-old alpacas, showed weight loss and diarrhoea before death or slaughter. The other cases showed no clinical signs of Johne's disease but 4 gave a positive result on faecal culture and one gave a positive result on testing with the caprine AGID assay and had acid-fast organisms in its faeces. At necropsy, all cases had grossly enlarged mesenteric lymph nodes. Johne's disease was diagnosed after histological examination of the lymph nodes with conventional culture and polymerase chain reaction testing of tissue samples. This report outlines the clinical, epidemiological, and pathological findings in these cases.

Fatal perinatal sarcocystosis in a lamb.

A 3-wk-old lamb died because of neurological disease. The predominant microscopic lesions were in the brain and spinal cord and consisted of nonsuppurative encephalomyelitis with severe gliosis throughout the gray and white matter. Immature and mature schizonts, 15.7 x 10.6 microns (8-30 x 6-18 microns), occurred in capillaries and were structurally similar to those of Sarcocystis tenella.

Assessment of a complement fixation test to detect Mycoplasma hyopneumoniae infection in pigs.

Serums from pigs slaughtered at abattoirs were tested for evidence of Mycoplasma hyopneumoniae infection using a complement fixation (CF) test which avoids the procomplementary effect of pig serum. To establish a diagnosis of enzootic pneumonia, the lungs from all sampled pigs were examined for pathological and histological changes consistent with the disease and cultures were made for mycoplasmas and bacteria. The study was carried out at Parkville and Bendigo 160 km apart at different times and all serums were tested at both laboratories. The results agreed closely. Thirty-six of 97 pigs at Parkville and 46 of 99 at Bendigo had enzootic pneumonia. About 80% were positive in the CF test. Sixteen per cent of porkers and 36% of baconers gave false negative reactors, that is, a negative test though lesions were present. About 18% to 36% gave false positive reactions but the level in the porkers in the Bendigo group was significantly higher (p less than 0.02). Possible explanations include, for the false negatives, loss of reactivity caused by circulating antigen and for the false positives, cross reacting antibody produced by another infection or failure to appreciate that lesions of EP were present in lungs because either they were not identified as such or they were not detected. The validity of any serological test for this disease cannot be established while there is a possibility that the present methods used for diagnosis, gross and microscopic examination and recovery of M. hyopneumoniae, fail to detect some infected animals. Other criteria may have to be adopted.

Multiple apparent Sarcocystis abortion in four bovine herds.

Foetuses recovered from multiple abortions in four dairy herds had multifocal nonsuppurative encephalitis, myocarditis and hepatitis. Focal placentitis was usually present. Sarcocystis-like protozoa were found in the brains of foetuses from two of the outbreaks. Apart from excess salivation in a few cows in one herd, farmers reported no clinical abnormalities prior to the abortions, and all cows remained normal after the abortions. Dogs and cats fed an affected foetus and neonatal calves from the affected herds failed to excrete protozoa in their faeces. The identity of the protozoa in the foetal brain was not confirmed.