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.

Pathology of a Bohle-like virus infection in two Australian frog species (Litoria splendida and Litoria caerulea).

Gross and histopathological examination was performed on seven captive magnificent tree frogs (Litoria splendida) and one green tree frog (Litoria caerulea) that had died or been humanely destroyed while naturally infected with Mahaffey Road virus, a Bohle iridovirus-like ranavirus. Necropsy examination revealed skin lesions consisting of multiple small pale or haemorrhagic papules and ulcers in most frogs. Other common gross findings were perineural haemorrhage affecting the spinal nerves, hydrocoelom, hepatomegaly and splenomegaly with pinpoint pale foci throughout the parenchyma. On histological examination, vasculitis with prominent endothelial necrosis was found in a wide range of tissues. Widespread lymphoid necrosis and fibroblast necrosis were usual findings. Multifocal epithelial cell necrosis in the epidermis, liver and pancreas was found commonly. Non-suppurative meningoencephalitis, myelitis and ganglioneuritis were present variably. Intracytoplasmic basophilic inclusion bodies were found variably in hepatocytes, renal tubular epithelium and keratinocytes. Immunohistochemistry demonstrated ranavirus antigen in endothelial cells, fibroblasts, macrophages, lymphocytes and epithelial cells in a wide range of tissues. The finding of widespread venous and lymphatic endothelial necrosis and demonstration of abundant endothelial antigen suggests that endothelial tropism of the virus plays a significant role in the pathogenesis of the infection.

Neuroaxonal dystrophy in Merino-Border Leicester × Polled Dorset lambs.

CASE REPORT: The clinicopathological features of neuroaxonal dystrophy (NAD) in 2 lambs are described. Of 40 Merino-Border Leicester × Polled Dorset lambs on a property in north-eastern Victoria, 4 presented with marked ataxia and listlessness, and 2 affected animals (2 days and 2 weeks of age, respectively) of both sexes were necropsied. Numerous axonal swellings (spheroids) were found in the central nervous system, particularly in brainstem nuclei and spinal cord grey matter, and there was severe spinal cord demyelination. CONCLUSIONS: This is the first report of NAD in such crossbred lambs; the affected animals were much younger than in previously described cases of ovine NAD and myelin loss was of much greater magnitude than previously reported.

Isolation and characterisation of a novel Bohle-like virus from two frog species in the Darwin rural area, Australia.

Twelve captive magnificent tree frogs Litoria splendida and 2 green tree frogs L. caerulea on a property in the Darwin rural area (Northern Territory, Australia) either died or were euthanased after becoming lethargic or developing skin lesions. Samples from both species of frog were submitted for histopathology and virus isolation. An irido-like virus was cultured from tissue samples taken from both species and was characterised using electron microscopy, restriction enzyme digests and nucleic acid amplification and sequencing. The isolates were determined to belong to the genus Ranavirus, were indistinguishable from each other and shared a 98.62% nucleotide similarity and a 97.32% deduced amino acid homology with the Bohle iridovirus over a 1161 bp region of the major capsid gene. This is the first isolation of a ranavirus from amphibians in the Northern Territory and the first report of natural infection in these 2 species of native frog. The virus is tentatively named Mahaffey Road virus (MHRV).

Neuroaxonal dystrophy in Australian Merino lambs.

Neuroaxonal dystrophy (NAD) is a morphological abnormality in man and animals that is characterized by the occurrence of numerous axonal swellings (spheroids) in the nervous system. NAD has been described in Suffolk lambs in the USA, Merino lambs in Australia and several breeds of sheep in New Zealand. This paper describes the clinicopathological changes of only the second occurrence of NAD reported in Merino lambs. There were some features (myelin loss, gliosis and visual impairment) in these Australian cases that have not been reported previously in ovine NAD. Application of immunohistochemical markers of axonal transport suggested that disruption of this transport mechanism contributed to spheroid development.

Yersiniosis in farmed deer.

Samples from 77 chital (Axis axis), 42 fallow (Dama dama), 26 red (Cervus elaphus), 7 rusa (Cervus timorensis) and 1 sambar deer (Cervus unicolor) were examined. Yersinia pseudotuberculosis infection was diagnosed as the cause of death in 6 (23%) of the red and 23 (30%) of the chital deer. Yersiniosis was the most common infectious cause of death diagnosed. Affected deer were usually found moribund or dead, often with faecal staining of the perineum. Gross pathology in chital included a fibrinous enterocolitis, enlarged congested mesenteric lymph nodes and multiple pale foci through the liver. Gross changes in red deer were limited to intense congestion of the intestinal mucosa and enlargement and congestion of mesenteric lymph nodes. Microscopic intestinal changes in both species consisted of microabscessation or diffuse suppurative inflammation of the intestinal mucosa with numerous bacterial colonies in the lamina propria. Multifocal suppurative mesenteric lymphadenitis was a common finding. Multifocal suppurative or non-suppurative hepatitis was frequently present in the liver of chital but was uncommon in the red deer. Yersiniosis occurred during the cooler months from June to November, with younger age classes most commonly affected. Y. pseudotuberculosis serotypes I, II and III were isolated in the ratio 17:3:0 in the chital deer and 1:1:2 in red deer. The clinical, epidemiological and bacteriological features are similar to those documented previously by New Zealand workers. The increased susceptibility to disease of red deer and chital compared to fallow deer and perhaps other species has not previously been documented.

Haemoglobinuria and hypophosphataemia in postparturient dairy cows without dietary deficiency of phosphorus.

Postparturient haemoglobinuria occurred in 11 Holstein-Friesian cows in 8 dairy herds in East Gippsland, Victoria. The affected cows had a wide range of ages, body condition and production level. Seven of 9 cows sampled were hypophosphataemic, 4 of 8 cows examined had Heinz bodies present in erythrocytes and strong ketonuria was present in 6 of 10 urine samples tested. Herdmates having similar calving dates had mostly normal serum phosphorus levels and none had Heinz bodies. There was no evidence for dietary phosphorus (P) deficiency, hypocuprosis or excessive P drain from high production being predisposing factors. There were no cruciferous plants in the diet. Haemolysis persisted in 4 cows despite treatment to raise serum P levels. An hyposthesis is proposed for the sporadic nature and clinical manifestations of the disease. This is based on mechanisms of hypophosphataemia occurring in man and mechanisms of Heinz body formation and haemolysis in other circumstances. We suggest that hypophosphataemia occurs following recovery from preparturient keto-acidosis caused by undernutrition in late pregnancy and then becoming nutritionally replete in the early postparturient period. Circulating oxidants may cause erythrocyte damage which may be predisposed to by hypophosphataemia.

Inherited epidermal dysplasia in Holstein-Friesian calves.

Inherited epidermal dysplasia (IED), formerly called baldy calf syndrome, is a lethal disease of calves of Holstein-Friesian ancestry. The disease causes progressive illthrift and skin, horn and hoof lesions, which can be confused with inherited zinc deficiency. The clinicopathological features and ancestry of 10 affected calves in Gippsland, Victoria are described.

Mannosidosis in Galloway calves.

Mannosidosis was diagnosed in four stillborn Galloway calves and an autolyzed full-term fetus from experimental matings of carrier animals. Gross lesions were moderate internal hydrocephalus, and pallor and enlargement of the liver and kidneys and arthrogryposis. Histologic changes in the central nervous system of each calf were marked foamy vacuolation of the cytoplasm of neurones in the cerebral cortex, thalamus and brainstem, and vacuolation of the Purkinje cells of the cerebellum. Spheroids were common throughout the brain and there was also consistent severe foamy cytoplasmic vacuolation of renal tubular epithelial cells and hepatocytes. The activities of alpha-mannosidase, the lysosomal enzyme whose activity is deficient in mannosidosis, and activities of five other lysosomal enzymes were compared in brain, liver, and kidney tissues of three mannosidosis-affected calves and normal calf tissues. Tissues from the affected calves had a marked deficiency of alpha-mannosidase activity compared with the normal tissues; the greatest deficiency was in the liver (99%) and brain (98%). Activities of the other lysosomal enzymes were elevated in the affected tissues compared with normal. Mannosidosis is a lysosomal storage disease that results from a defect in glycoprotein metabolism and affects man, Angus and Angus-related breeds of cattle, such as Murray greys, and the cat. The congenital disease is caused by an inherited deficiency of the lysosomal enzyme alpha-mannosidase, and is inherited in an autosomal recessive manner. Mannosidosis was recently reported in a number of aborted and stillborn Australian Galloway calves from an experimental breeding trial. This is more detailed account of the histological and biochemical results obtained during the trial.

Skin ulcers caused by Mycobacterium ulcerans in koalas near Bairnsdale, Australia.

Skin ulcers were found in 7 koalas from Raymond Island in the Gippsland Lakes of southeastern Australia. Ulcers in 4 koalas showed loss and underrunning of cutaneous tissue, with coagulative necrosis of subcutaneous tissue. These lesions contained large numbers of acid-fast bacilli, and areas of granulation tissue formation and superficial inflammation were present. Mycobacterium ulcerans was isolated from 2 of these animals. The ulcers from the other 3 koalas contained both M. ulcerans and M. scrofulaceum, and in these the necrotic tissue was surrounded by a granulomatous reaction which, in one case, extended into bone. Four of the koalas had more than one ulcer. The possible origin of the infections is discussed.

Diagnostic studies of the fetus, placenta and maternal blood from 265 bovine abortions.

During 1981, the fetus, placenta and maternal serum were received from each of 265 bovine abortions. These specimens were examined using histopathological, histochemical, bacteriological, mycological, endocrinological, immunological, serological and virological techniques. The cause of abortion was identified in 98 (37%) cases. Of these diagnosed abortions 27 (28%) were due to infection with fungi, 17 (17%) to Salmonella spp, 11 (11%) to Campylobacter fetus and 10 (10%) to Corynebacterium pyogenes infection. Of the remaining 33 (34%) diagnosed abortions 8 were due to Leptospira sp, 5 due to protozoan (probably Sarcocystis) encephalitis and 20 due to miscellaneous bacterial infections (including Brucella abortus) and fetal deformities. Bovine virus diarrhoea virus was isolated in 5 (2%) abortions, however the significance of the isolations was not known. Infectious bovine rhinotracheitis virus and chlamydia were not identified as causal agents in any abortion. In 18 (7%) abortions no definite etiologic agent was identified despite pathological findings suggestive of infection. Fetal heart blood serology and immunoglobulin values were not reliable indicators of infectious abortion. Of the remaining 149 (56%) abortions, 17% had high maternal serum cortisol levels and twin fetuses occurred in 9%.

Outbreaks of photosensitisation and deaths in cattle due to Myoporum aff. Insulare R. Br. toxicity.

Outbreaks of photosensitisation and deaths in cattle on 5 farms in Victoria occurred following access to Myoporum affinity insulare. Signs were observed 2 to 6 days after access to myoporum trees or pruned branches and included depression, anorexia, photosensitisation, constipation, agalactia, jaundice, and mucosal petechiation. Serum gamma glutamyl transferase and aspartate amino transferase levels were elevated in all cases. Gross findings in fatally intoxicated cows consisted of widespread haemorrhages and pale yellow mottling of the liver. Distinctive histological lesions of periportal hepatic necrosis and bile duct proliferation were seen in all cases. An 8-month-old heifer given 30 g/kg fresh minced leaves by stomach tube died approximately 70 h after initial dosing. Post-mortem findings of widespread haemorrhage and hepatic periportal necrosis and bile duct proliferation were identical to those of field cases.