An estimate of specificity for a Johne's disease absorbed ELISA in northern Australian cattle

Objective To estimate the specificity of an absorbed enzyme-linked immuno-sorbent assay kit^d for Johne's disease (JD) when used in mature cattle populations resident in northern Australia.
Design Blood samples were collected from beef cattle in northern Queensland, the Northern Territory and northern Western Australia, and from dairy cattle in northern Queensland. The specificity of a serological test for JD was estimated by testing the blood samples with an absorbed ELISA kit. Further samples were collected from cattle with positive ELISA results to determine the presence or absence of infection with Mycobacterium avium subsp paratuberculosis .
Procedure During 1995 and 1996, blood, tissue and gut contents were collected from beef cattle at abattoirs in Queensland and the Northern Territory; and blood and faecal samples were collected from dairy cattle in herds assessed to be most at risk for JD in northern Queensland. The blood samples were tested using an absorbed ELISA kit. Tissues and gut contents from beef cattle that had positive ELISA results were cultured for M avium subsp paratuberculosis , and tissues were examined histo-logically. Faecal samples from dairy cattle with positive ELISA results were cultured for M avium subsp paratuberculosis .
Results Estimates of specificity for this absorbed ELISA in mature northern Australian cattle were 98.0% (97.0 to 98.8%, 95% CI) in beef cattle, and 98.3% (96.7 to 99.3%, 95% CI) in dairy cattle.
Conclusion Estimates of specificity in this study were lower for beef cattle from the Northern Territory and northern Western Australia and for dairy cattle from northern Queensland than those quoted from studies on cattle in southern Western Australia. This should be considered when serological testing using the JD ELISA is carried out on northern Australian cattle.     

Influence of head posture on the respiratory tract of healthy horses

Twenty four normal, confined mares were unable to lower their heads for 24 or 48 h. In 21 mares this resulted in increases in the proportion of neutrophils and/or numbers of bacteria in transtracheal aspirates. In eight mares the changes in tracheal washes were accompanied by clinical evidence of mild respiratory disease. In three additional cases respiratory signs were accompanied by systemic illness. These changes reversed once the mares were able to lower their heads. Haematological changes (absolute neutrophilia and/or hyperfibrinogenamia) were mild and occurred more commonly in horses restrained for 48 h. The results suggest that keeping the heads of healthy horses raised leads to an increased bacterial burden in their tracheobronchial secretions. These changes appeared to be related to head posture effects and not simply confinement in stocks. These findings give further weight to the theory that postural drainage may facilitate clearance of bacteria from the tracheobronchial tree. The possible relevance of such findings to post-transportation pneumonia in horses is discussed.     

Indices of renal function: values in eight normal foals from birth to 56 days

A series of blood and urine samples was collected from each of eight normal foals between birth and eight weeks. Blood chemistry relating to renal function was evaluated as well as physical and chemical characteristics of urine. During the first 4d of life it was impractical to suggest meaningful normal values due to wide variation among foals and with time. Serum urea and plasma creatinine fell markedly to levels less than those previously reported for normal adult horses, while urine, mildly hypersthenuric at birth, rapidly became hyposthenuric. There was also a marked proteinuria during the first 48h. After 4d clinicopathological values stabilised. Urea and creatinine remained at subadult levels and hyposthenuria was maintained. While there was some variation with time, generally the urinary activity of gamma-glutamyl transpeptidase (GGT) and alkaline phosphatase (AP) was greater in foals than in adults; plasma potassium, the creatinine clearance ratio of potassium (% Cr K), serum inorganic phosphate and the creatinine clearance ratio of phosphate (% Cr PO4) were greater than in adults while plasma chloride and the creatinine clearance ratio of chloride (% Cr Cl) were lower in foals than in adults. Urinary pH was acidic and epithelial cells and calcium oxalate crystals more prevalent in the urine of foals than in that of adults. The information presented here will be useful in the diagnosis and management of renal disease and azotaemia in foals.     

Artificial Propagation and Induction of Triploidy in Largemouth Bass Micropterus salmoides and Ploidy Discrimination using Erythrocyte Length

We describe an artificial propagation procedure and simple ploidy discrimination techniques using erythrocyte major axis length for largemouth bass Micropterus salmoides. Hormonal treatments of 5 mg/kg of carp pituitary and 50 μg/kg of leutinizing hormone-releasing hormone (LHRH) produced viable gametes in 21-24 h, and triploidy was induced using a pressure treatment of 563 kg/cm² on embryos for a 1-min duration exactly 5 min following fertilization. We produced about 500 fingerling triploids and about 500 diploid controls, and verified genetic status of a subset of each group using flow cytometry. Erythrocyte length was measured for 10 known diploid and 10 known triploid individuals. Remaining fish were internally microtagged with group-specific tags and mixed to test the model. We developed ploidy discrimination intervals based on the 99% confidence limits of mean erythrocyte length (MEL, N = 25 erythrocytes) for individual fish, which were 14.43-16.66 μ.m for triploids, and 10.23-13.62 μm for diploids. Logistic regression provided the discrimination model: Ploidy status (±) = -196.16 + 13.97 x MEL, with positive (+) outcomes considered triploid. Both discrimination techniques were 100% effective at differentiating ploidy of the 22 microtagged largemouth bass recollected from the mixed population. We did not observe a significant change in erythrocyte length as fish size increased, indicating that erythrocyte length is an accurate predictor of ploidy for all sizes of largemouth bass.     

A role for DNA characterisation in ovine footrot

Bacteroides nodosus involved in several outbreaks of ovine footrot over a number of years were subjected to DNA restriction endonuclease analysis. Individual isolates were found to have characteristic Bam HI profiles which permitted their accurate identification and differentiation from other isolates. Bam HI profiles of B. nodosus isolates were used in epidemiological investigations involving consecutive outbreaks of footrot on individual and neighbouring farms. The relationship of given isolates to a common source could be established by this means. Restriction endonuclease analysis provides an additional epidemiological tool in ovine footrot investigations as it accurately identifies interstrain differences in a manner not possible by conventional bacteriological and serological means.     

Tuberculosis in alpaca (Lama pacos) on a farm in Ireland. 2. Results of an epidemiological investigation

Tuberculosis (TB), due to infection with Mycobacterium bovis was diagnosed in a flock of alpaca in Ireland in 2004. An epidemiological investigation was conducted to identify the risk of TB for farmed alpaca where TB is endemic, the origin of the infection, the potential for alpaca-to-alpaca transmission and appropriate control measures. The investigation focused on the alpaca flock (including the farm, animal movements and breeding, feeding and flock health practice), the disease episode (including animal disease events and subsequent control measures) and TB infection risk in the locality. The TB risk to alpaca is high in areas where infection is endemic in cattle and badgers and where biosecurity is inadequate. It is most likely that the source of infection for the alpaca was a local strain of M. bovis, present in cattle in this area since at least 2001. Genotyping of isolates identified a single variable number tandem repeat (VNTR) profile in both cattle and alpaca in this region. Although a tuberculous badger was also removed from the vicinity, bacterial isolation was not attempted. On this farm, infection in alpaca was probably derived from a common source. Alpaca-to-alpaca transmission seems unlikely. Two broad control strategies were implemented, aimed at the rapid removal of infected (and potentially infectious) animals and the implementation of measures to limit transmission. Tests that proved useful in detecting potentially-infected animals included measurement of the albumin-to-globulin ratio and regular body condition scoring. Skin testing was time consuming and unproductive, and early detection of infected animals remains a challenge. The flock was managed as a series of separate groupings, based on perceived infection risk. No further TB cases have been detected.