A Rosenthal fiber encephalomyelopathy resembling Alexander's disease in 3 sheep

We report an encephalomyelopathy in three 18-month-old Merino sheep with features of adult-onset Alexander's disease (AD), a human primary astrocytic disorder. The signature histologic finding was the presence of numerous hypereosinophilic, intra-astrocytic inclusions (Rosenthal fibers), mainly in perivascular, subpial, and subependymal sites, especially in the caudal brain stem and spinal cord. Although AD usually results from mutations in the glial fibrillary acidic protein (GFAP) gene, no such mutation was detected in these sheep. However, the annual clinical presentation of this disorder in a few sheep in the affected flock is suggestive of a familial pattern of occurrence.     

Immune responses of sheep to louping-ill virus vaccine

The immune responses of sheep to single and double doses of commercially available louping-ill virus vaccine were examined. The susceptibility to challenge of sheep which had been vaccinated but showed a poor response was also investigated. Two injections of vaccine were required to provoke an adequate antibody response and maximum titres were obtained when there was an interval of two to eight weeks between injections. After challenge, viraemia could not be detected in animals with an antibody titre of 20 although increase in the concentration of humoral antibodies indicated that infection had occurred. Vaccinated but seronegative sheep and vaccinated animals with an antibody titre of 10 were also clinically resistant to the challenge, although circulation of virus was demonstrated. That vaccination had sensitised those animals to viral antigen was evident from the reduced viraemias, the early rise in humoral antibody titres and subsequent protection afforded compared to unvaccinated control animals. Thus, animals with minimal antibody titres after vaccination are protected, but it is recommended that vaccines eliciting the highest possible antibody responses will be the most useful under field conditions.     

Myopathy of dogs resembling white muscle disease of sheep

Automation of the complement fixation test for diagnosing Brucella abortus infection in cattle has allowed this difficult, time-consuming and labour-intensive hut most specific test to he used for large scale serodiagnosis in New Zealand's Brucellosis Eradication Scheme. The automated test has the advantages of eliminating much human error, of improving accuracy and of reducing the costs of labour and reagents.

The Auto-Analyzer performs a warm complement fixation test at a single serum dilution. Each batch of 39 serum samples is compared with a standard positive control serum with a complement fixing antibody activity equivalent to 1/30 of the second International Standard Ani-Brucella abortus Serum. All sera with an antibody level equal to, or greater than, the standard serum are regarded as positive to the test. A titre for serum tested by the automated method is not obtained, and positive sera that prozone strongly may be recorded as negative. Where necessary, the semi-automated microtitre complement fixation test is used to delineate titres and the status of doubtful automated CFT results. The automated and microtitre complement fixation tests use the same reagents; only relative concentrations differ.     

Caprine arthritis-encephalitis in the Basque country, Spain

A goat herd severely affected by arthritis was studied. The most representative clinical signs consisted of articular swelling, mainly of the carpal joints, and the subsequent locomotor disorders. Some goats also showed signs of central nervous system involvement. Examinations of joint fluid revealed an increased number of mononuclear blood cells, mostly lymphocytes. Gross and microscopic articular lesions were of inflammatory and degenerative types. Periarticular connective tissue, synovial bursae, tendons and tendon sheaths were predominantly affected. Inflammatory lesions were those of a chronic hyperplastic tenosynovitis with fibrosis of the connective tissue components. Degenerative changes consisted mainly of necrosis and mineralisation of articular-related structures. Histological lesions in the central nervous system were those of a nonpurulent encephalitis initially located in periventricular areas, but in one case extensive encephalomalacia was also seen. Of the 80 animals sampled 82.5 per cent showed seropositive reactions against an ovine progressive pneumonia virus antigen. None was seropositive to brucella and titres to chlamydia were low. Attempts to isolate chlamydia and mycoplasma from affected joints and several organs failed. Different bacteria were recovered from a few samples but did not seem significant. Syncytium-forming viral particles were isolated from several organs, mainly the lungs, synovial membranes and lymphoid tissue of almost all the slaughtered animals. These particles were identified as lentiviruses by electron microscopy. The clinical signs, lesions serological results and microbiological findings, led to a diagnosis of caprine arthritis-encephalitis. This syndrome has not been recognised in Spain previously.     

Age-specific seroprevalence of Border disease virus and presence of persistently infected sheep in Basque dairy-sheep flocks

Using p125/p80 antibody and antigen-ELISA tests, age-specific seroprevalence and presence of persistently infected (PI) sheep were investigated in six commercial latxa dairy-flocks, housed for variable periods. The flocks all had a recent history of Border disease (BD). Every flock included seropositive sheep and seven 0.5-3-year-old PI sheep were detected in two of four flocks tested. Age-specific antibody patterns differed according to the presence or absence of PI sheep in the flock. In flocks free of PI sheep, seroprevalence was 6-13% in 1-year-old sheep and 42-93% in older sheep. In contrast, seroprevalence was 67-99% in sheep raised with PI sheep for at least 1 year and 29-33% in replacement 0.5-0.6-year-old sheep (including a PI sheep) indicating that Border disease virus (BDV) transmission in Basque dairy-flocks can be relatively slow. Moderate seroprevalence in young replacement sheep should not discourage further testing to detect PI sheep, and our results highlight the risk of failing to achieve "natural vaccination" prior to pregnancy by mixing PI sheep with BDV-unexposed ewes.     

Immunosuppression in toxoplasmosis: studies in sheep with vaccines for chlamydial abortion and louping-ill virus

Toxoplasma gondii infection was established in sheep seven days (acute infection) or 28 days (chronic infection) before they were given enzootic abortion (EAE) vaccine alone or simultaneously with louping-ill (LI) vaccine. Uninfected controls received the same vaccination schedule. The serological response of acute toxoplasma-infected sheep to initial LI vaccination was significantly depressed but after revaccination four weeks later these sheep demonstrated a response equal to that of the revaccinated controls. Infected sheep also gave a significantly poorer response to EAE vaccine than control animals, the effect being more marked in those with chronic infection. Revaccination evoked no clear response in any group but on three of five sampling days antibody titres of controls were significantly higher than those of infected sheep.     

A syndrome of hepatogenous photosensitisation, resembling geeldikkop, in sheep grazing Tribulus terrestris

Two outbreaks of photosensitivity disease occurred in weaner sheep in south western New South Wales during early autumn 1982. In each instance there was a history of access to the annual herb, Tribulus terrestris and both the clinical and pathological findings were consistent with geeldikkop, a major disease in the Republic of South Africa. The prevalence rates of clinical cases were 21 and 37%, while the case fatality rates approached 70%. Clinical signs were dominated by jaundice and photosensitisation. Ochre and khaki discolouration were present in the liver and kidneys, respectively. Histopathologically, the most characteristic lesion was the presence of acicular, cholesterol-like clefts in the lumens of bile ducts and in the cytoplasm of hepatocytes and Kupffer cells. Similar structures were also evident in the lumens of nephrons in association with segmental hyperplasia of the neighbouring tubular epithelium. The possible pathogenesis of the hepatogenous photosensitisation and its resemblance to geeldikkop are discussed.     

A clinical study of periodontal disease in sheep

Detailed examinations were made of the central permanent incisors and periodontia of 30 or 40 ewes on each of one control farm and three periodontal disease (P.D.) farms. The study confirmed that incisor crown lengthening, protrusion and loosening were significant features of P.D. Periodontitis (assessed by increased sulcus depth and bleeding after probing) about the lingual sulcus was a significant feature of P.D. Labial gingivitis and labial periodontitis were not significant features. A relatively long lower jaw did not appear to be a feature of P.D. 87.