Seroprevalence of antibodies to Pestivirus infections in South Australian sheep flocks.

OBJECTIVE: Bovine viral diarrhoea virus (BVDV) and border disease virus (BDV) are of the genus Pestivirus. They are known to cause significant reproductive and production losses, with BVDV acknowledged as a major source of economic loss to the Australian cattle industry. Very little is currently known about the prevalence and effect of pestiviruses in the Australian sheep industry. The present study aimed to examine the seroprevalence and effect of both BVDV and BDV in South Australian sheep flocks. METHODS: In total, 875 breeding ewes on 29 properties were serologically tested by ELISA, AGID and VNT assays for the presence of Pestivirus-specific antibodies. RESULTS: Three (0.34%) individual animals returned serological results suggestive of previous BDV infection. All three positive animals were collected from one property, giving a property level seroprevalence of 3.45% and a within-flock seroprevalence of 10%. CONCLUSION: The results suggested that BDV infection is present, albeit at a very low incidence, in the South Australian sheep flock and BVDV infection appears to be absent. Consequently, pestiviruses are unlikely to impair production in South Australian sheep populations.

BVDV in Australian alpacas: natural infection and clinical profiles following co-mingling with a persistently infected heifer.

BACKGROUND: Although predominantly a disease of cattle, bovine viral diarrhoea virus (BVDV) is known to infect other ruminant and camelid species such as sheep and alpacas. The aims of this study were to determine if BVDV-naive alpacas would become acutely infected and seroconvert to the predominant Australian strain of BVDV following co-mingling with a BVDV-1c persistently infected (PI) heifer and to determine what, if any, clinical signs, haematological responses and selected biochemical changes occur with acute BVDV-1c infections in alpacas. METHODS: A PI heifer and four alpacas co-mingled for 2 weeks. Weekly blood samples were collected and twice weekly clinical examinations were performed on the alpacas. RESULTS: Serum analysis by antibody ELISA indicated that all four alpacas were positive for BVDV-specific antibodies between 35 and 54 days after mixing with the BVDV-1c PI heifer. Viral antigen was detected by antigen ELISA in two alpacas on days 21 and 35 after initial mixing. In general, all the physical clinical parameters measured were normal. Serum biochemical and haematological analyses in two of the alpacas revealed marginally low sodium, chloride and elevated potassium concentrations, a lymphocytosis, monocytosis and a neutrophilia at some point during the study period in either one or both of the alpacas. CONCLUSION: This study showed that infection in Australian alpacas readily occurs when a BVDV-1c PI bovine co-mingles with naive alpacas and that acute infections are clinically mild and undetectable without serological testing.

Antibodies to bovine viral diarrhoea virus (BVDV) in water buffalo (Bubalus bubalis) and cattle from the Northern Territory of Australia.

BACKGROUND: Farmed and feral water buffaloes (Bubalus bubalis) populations often coexist with cattle in the Northern Territory of Australia, but their level of exposure to bovine viral diarrhoea virus (BVDV) is unknown. METHODS: Water buffalo (n = 245) and cattle (n = 184) serum samples were collected by the NT Government as part of an ongoing disease surveillance scheme at varying intervals between 1993 and 2001. All samples were frozen and stored at -80°C until testing. Water buffalo samples from farming properties were identified as 'farmed' animals and the remaining samples as 'feral' populations. Serum samples were analysed using commercially available ELISAs to test for the presence of BVDV antibodies. RESULTS: Testing of historical water buffalo sera for BVDV antibodies revealed a low level of exposure, with 4.5% (95% CI ± 2.6%) being sero-positive; cattle from the same geographical area and time period had higher levels of exposure at 74.5% (95% CI ± 6.3%). DISCUSSION: This survey showed that water buffalo are susceptible to infection with BVDV. No persistently infected water buffalo were identified in this study.

Cross-sectional observational survey of serum biochemistry values in a population of 69 adult female alpacas (Vicugna pacos) in South Australia.

Blood samples were collected from 69 'healthy' female alpacas aged ≥12 months from 11 properties in South Australia. The 10-90 percentile ranges of the 16/19 analytes measured in this sample population were within the published ranges of four healthy alpaca populations from other geographic locations. Marginal exceptions were glutamate dehydrogenase and bicarbonate. Potassium was notably elevated, probably because of haemolysis of some samples. The sample size was insufficient to provide the appropriate statistical power to define diagnostic references ranges according to international standards. The health status of the sample population of alpacas was presumptive based on a physical examination.

Serological survey for antibodies against bovine viral diarrhoea virus and Neospora caninum in a population of South Australian alpacas (Vicugna pacos).

OBJECTIVE: Bovine viral diarrhoea virus (BVDV) and Neospora caninum may cause clinical disease in alpacas. Both diseases are present in the Australian cattle population. The objective of this study was to perform a serological prevalence survey for BVDV and N. caninum exposure in a regional alpaca population of South Australia. METHODS: Serum samples were taken from 182 alpacas on 10 farms, which had a combined population of 1308 alpacas. Serological analysis for BVD antibodies was performed using a competitive BVDV antibody ELISA kit. Serological analysis for N. caninum was performed using an anti-Neospora ELISA with a protein G conjugate. RESULTS: Of the 182 alpacas sampled, 5 animals located on three properties were positive for BVDV antibodies, constituting a prevalence of 2.7% (95% confidence interval 1-6%). All samples tested negative for N. caninum antibodies. CONCLUSION: There is a low BVDV seroprevalence and N. caninum is currently either absent or present at a very low prevalence in this population of alpacas in South Australia. There is serological evidence for the presence of both organisms in South Australian beef and dairy cattle herds. Appropriate biosecurity protocols to minimise the risk of introduction and exposure should be a high priority to maintain this favourable status.

The Shetland Islands scrapie monitoring and control programme: analysis of the clinical data collected from 772 scrapie suspects 1985-1997.

There were 574 scrapie positive suspects (histopathological scrapie lesions present) and 198 scrapie negative suspects (histopathological scrapie lesions absent). The greatest number of scrapie cases were recorded in sheep of 2, 3 and 4 years of age which represented 17%, 36% and 23% of the scrapie positive suspects, respectively. The sign sensitivities and specificities for the ten recorded signs were, respectively: pruritus (62%, 42%), ataxia (23%, 74%), hyperaesthesia (32%, 74%), wool loss (25%, 73%), fleece discolouration (29%, 85%), bruxism (23%, 69%), nibbling reflex (17%, 58%), head rubbing (47%, 78%), poll rubbing (25%, 83%). These single signs had poor discriminatory values with likelihood ratios close to one (range 0.89-1.21); combinations of the four signs, pruritus, wool loss, ataxia, hyperaesthesia and emaciation were more discriminatory (range 0.30-4.3). This study covered a time period when bovine spongiform encephalopathy (BSE) might have been introduced into the sheep population on the Shetland Islands via contaminated feed. No temporal changes could be detected in the age structure of the affected animals.

Controlled clinical trial of the effect of a homoeopathic nosode on the somatic cell counts in the milk of clinically normal dairy cows.

Cows in a 250-cow Holstein-Friesian herd were allocated at random to be treated with either a homoeopathic nosode or a negative control, both treatments being applied by means of an aerosol spray to the vulval mucous membranes. A total of six treatments were given over a period of three days and milk samples were taken for the determination of somatic cell counts (SCC) on days -3, 3, 7, 9, 14, 21 and 28. Individuals applying the treatments or carrying out the SCC determination were unaware of which animals were receiving which treatment. Owing to the wide natural variations in SCC, the trial had only a 71 per cent possibility of detecting a 30 per cent difference in SCC between the two groups. There were no significant differences between the SCC of the two groups on any sample day, but there were significant variations between the SCC on different days (P=0.003) in both groups.

The similarity of the physical sign frequencies of bovine spongiform encephalopathy and selected differential diagnoses.

This paper describes a method which enables the similarity of diseases based upon their physical sign frequencies to be defined relative to bovine spongiform encephalopathy (BSE). The means of the absolute differences between the sign frequencies of BSE and the differential diagnoses were used as measure of similarity. Four sets of signs were compared. The most useful quantitative measurement of difference between the diseases was achieved when only the variant signs were used. Diseases that have a high similarity to BSE when the variant signs are compared are more likely to have case presentations that approximate to those found in BSE. These are the diseases that are most likely to be confused with BSE by clinicians. Previously published BSE differential diagnoses from clinical opinion and brain histopathology are reported and compared to the diseases used in this study.

Clinical sign profile likelihood ratios for bovine spongiform encephalopathy suspects.

This study has described a method for generating the probability of a bovine spongiform encephalopathy (BSE) suspect being a true positive BSE case. A weighting equivalent to the clinical sign frequencies recorded in histopathologically confirmed BSE cases was assigned to 14 clinical observations and a clinical profile score for the case was generated by the summation of the weightings. This method was applied to 50 histopathologically confirmed (true positive cases) BSE suspects and 50 histopathologically unconfirmed (false positive cases) BSE suspects. The profile scores for the true positive BSE suspect cases were statistically significantly higher than the profile scores of the false positive BSE suspect cases (P = 0.0014) using a Mann-Whitney U non-parametric test. The mean profile score for the true positive cases was 944 and for the false positive scores was 879. Likelihood ratios for BSE suspects with different clinical profile scores were computed using different clinical profile score cut off point and ranges. A BSE suspect with profile score of 727 or above (the lowest cut off point) and 1037 or above (the highest cut off point) had likelihood ratios for being BSE of 1. 09 and 4.00 respectively. The likelihood ratios for a BSE suspect being a true positive BSE case in the profile score ranges 627-866, 867-966, 967-1036 and 1037-1067 were 0.35, 1.06, 1.30 and 4.0 respectively. Further investigations or a revisit may be justified in animals with a low probability of being BSE.

An intermediate-technology pattern matching model of veterinary diagnosis.

An intermediate-technology pattern matching model and decision support system for veterinary diagnosis is described. Six diseases of cattle occurring in the tropics are used to illustrate the model. The pattern matching model is composed of a series of transparent overlays and a template. Each transparent overlay represents a sign state and contains sign frequency information for the diseases on the template. By superimposing multiple transparent overlays upon the disease template, a ranked list of differential diagnoses can be obtained. Ranking is by summation of disease sign frequencies. Modifications to accommodate observational uncertainty are presented. Disease prevalences can be represented in the model.

Pattern-matching models for the differential diagnosis of bovine spongiform encephalopathy.

This study assessed the performance of a system for making decisions about the diagnosis of bovine spongiform encephalopathy (BSE). The system consisted of four pattern-matching models. The sensitivity, specificity, likelihood ratios and accuracy of each model were determined by using clinical descriptions of 100 suspect BSE cases which had been submitted for brain histopathology by veterinary officers of the Ministry of Agriculture, Fisheries and Food, 50 of which were true positive cases (confirmed by histopathology) and 50 false positive cases (not confirmed by histopathology). The clinical description of each case consisted of 14 clinical signs, each of which was defined as either present or absent. The system compared the case descriptions with the profiles of possible differential diagnoses, each profile consisting of the frequency of occurrence of the same 14 clinical signs. The pattern-matching models used the sums of the sign frequencies to rank the differential diagnoses. Models 1 and 2 derived information only from the presence of signs; models 3 and 4 derived information from the presence and absence of signs. Models 2 and 4 excluded diagnoses which did not have in their profile a sign which was observed, and diagnoses which had a sign in their profile which should always be present according to the profile description but which was not observed. The best performances by the models were: sensitivity 96 per cent (model 1 and model 2), specificity 72 per cent (model 4), accuracy 72 per cent (model 4), likelihood ratio of a positive test 2.00 (model 4), likelihood ratio of a negative test 0.21 (model 4).

Hypocalcaemia in 23 ataxic/recumbent ewes: clinical signs and likelihood ratios.

Twenty-three ewes in a flock of 2000 were identified as having acute onset ataxia and/or having become recumbent in late pregnancy and early lactation. The presence or absence of 15 clinical signs were recorded. Thirteen of the ewes (57 per cent) were hypocalcaemic and 10 (43 per cent) were normocalcaemic. In the hypocalcaemic group, loss of anal reflex, constipation, tachycardia, hyposensitivity, ruminal stasis, ruminal tympany, salivation and tachypnoea were recorded in 50 per cent or more of the cases. In the normocalcaemic group, tachycardia, tachypnoea and ataxia were recorded in 50 per cent or more of the cases. Constipation, ruminal stasis, salivation and hyposensitivity had likelihood ratios of 3 and above for being associated with hypocalcaemia. Ruminal stasis and hyposensitivity had the likelihood ratios of 0.10 and 0.11 respectively for not being associated with hypocalcaemia.

Focal cystic endometrial hyperplasia in a bitch.

Rapid abdominal enlargement and weight gain occurred in a four-year-old Rhodesian ridgeback bitch in late oestrus. The bitch was nulliparous. Severe cardiovascular dysfunction followed and an exploratory laparotomy was performed. A large, single, spheroid mass weighting 17 kg was located in the middle section of the left uterine horn. A diagnosis of sterile, focal, cystic endometrial hyperplasia was made from gross pathology, histopathology and bacteriology. The bitch made a complete recovery following an ovariohysterectomy.