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1.
van den Oord QG van Wijk EJ Lugton IW Morris RS Holmes CW 《New Zealand veterinary journal》1995,43(7):328-332
Two groups of six mature brushtail possums (Trichosurus vulpeculu) were housed in two respiration chambers, and their heat production, whole body conductance and lower critical temperatures were measured under a variety of simulated weather patterns. The possums were subjected to ambient temperatures of 30, 20 and 3 degrees C. At 20 and 3 degrees C, the animals were exposed to near still air and light winds (wind speed 0.8 and 6.7 km/h), both with, and without, simulated rain every 8 hours. The lower critical temperature in near still air lies between 7 and 10 degrees C. This temperature increases by about 2, 6 and 8 degrees C respectively for a wind velocity of 6.7 km/h, simulated rain and a combination of the two factors. Weather in New Zealand, especially in the cooler part of the year, will often produce conditions below the lower critical temperature of the thermoneutral zone of possums. This will necessitate significant increases in metabolic rate and hence food consumption or mobilisation of body fat reserves, which if not sustainable will result in the death of possums. Field studies have shown that this is often the case in the wild. It is proposed that this stress may be sufficient to decrease the resistance (especially cell-mediated immunity) of some possums and allow acceleration of the disease process in those infected with Mycobacterium bovis. 相似文献
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AIMS: This study was initiated to investigate aspects of the epidemiology, pathogenesis and transmission of tuberculosis in wild red deer, with the aim of determining whether this species may be considered a reservoir host of Mycobacterium bovis in New Zealand. METHOD: One hundred and six wild red deer (Cervus elaphus) carcasses from the Castlepoint and Hauhungaroa Range areas, which are endemic for bovine tuberculosis, were examined for the presence of M. bovis infection. Samples were also examined from 46 skin test-positive farmed deer killed at two deer slaughter premises. Where possible, a standard set of tissues and excretion site samples was collected for mycobacteriological examination. RESULTS: Fifty-eight infected deer were identified, and of these 28% showed no gross lesions. The prevalence of tuberculosis confirmed by culture in the wild deer was 32%. Only one of 18 deer younger than 1 year was infected. Mature deer (>2 years) were 12 times more likely to be infected than those under 1 year of age. Infected older deer were less likely to show typical gross lesions than younger animals. Mycobacterium bovis was isolated from the oropharyngeal tonsil of 34 of 56 (61%) of the infected deer, and this was the most commonly infected site. Gross lesions were found in 18 of the 34 infected tonsils and only one of these showed a purulent tonsillitis. Mycobacterium bovis was recovered from four of 53 nasopharyngeal tonsils, four of 53 oropharyngeal swabs, one of 53 tracheal and nasal swabs, and one of 46 faecal samples, but not from any urine specimens. CONCLUSION: These findings suggest that significant bacillary excretion from infected deer was uncommon, and is more likely to occur in severely affected animals. This study has confirmed the importance of mucosa-associated lymphoid tissues (MALT), particularly the oropharyngeal tonsil, in the pathogenesis of tuberculosis in deer. The findings justify investigation of the hypotheses that the prevalence of tuberculosis in wild deer in New Zealand is high due to transmission of infection from possums, and that in the absence of an infected possum population, the prevalence of tuberculosis in deer is likely to be low, and spatially patchy. CLINICAL RELEVANCE: The results suggest that about one quarter of infected deer show no detectable gross lesions. This implies that many infected carcasses may enter the food chain unrecognised and that the estimated sensitivity and specificity of diagnostic tests may be erroneous if there is a difference in test performance between those conducted on deer with or without gross lesions. Diagnostic sensitivity following slaughter may be improved by routine culture of oropharyngeal tonsils and careful examination of lungs for adhesions and small subpleural tubercles. 相似文献
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Lugton IW 《Australian veterinary journal》2004,82(8):490-496
Published information on aspects of the epidemiology of paratuberculosis was reviewed to examine the hypothesis that clinical expression of disease may be induced by deficiencies or imbalances of micronutrients. The progression of paratuberculosis and the development of clinical signs, although innately linked with the process of becoming infected with Mycobacterium avium subsp paratuberculosis, are mostly controlled by factors other than those predisposing to the acquisition of the organisms. There is strong evidence in the literature reviewed to suggest that soil acidification, excesses of iron and molybdenum, and deficiencies in copper and selenium and possibly other minerals and trace elements have a role in the disease process. The fact that no single nutritional supplement has been consistently found to produce clinical recovery suggests that the causal role of these factors is complex and may vary depending upon the geochemical environment. Altering the nutritional environment by appropriate trace element supplementation and liming, as well as decreasing the reliance on shallow-rooted pastures needing frequent fertiliser applications may assist in controlling the clinical expression of paratuberculosis. Such measures could produce a significant decrease in the incidence of clinical expression across flocks and herds. 相似文献
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Natural infection of red deer with bovine tuberculosis 总被引：2，自引：2，他引：0
Lugton IW Wilson PR Morris RS Griffin JF de Lisle GW 《New Zealand veterinary journal》1997,45(1):19-26
Six bovine tuberculosis-free red deer hinds were introduced in October 1993 to a 1.8 ha enclosure, within a larger field study site known to contain tuberculous possums, and kept there for 9 months. A Mycobacterium bovis-infected possum was found in the vicinity of the deer enclosure 3 weeks after the introduction. Subsequently, a further eleven infected possums were found in the area. The deer were monitored by repeated composite antibody detection ELISA and lymphocyte transformation assays for tuberculosis, interpreted in parallel, by skin testing and by routine culturing of samples collected from potential excretion sites. Lymphocyte transformation assay evidence of M. bovis infection in four hinds was first observed 4 months after introduction. One other hind became bovine tuberculin lymphocyte transformation assay positive in the 5th month. Positive or equivocal bovine reactivity remained evident at most test episodes. A comparative cervical skin test performed in July 1994, shortly before slaughter, was positive in these five hinds. Mycobacterium bovis was recovered off swabs from the oropharyngeal tonsils of two hinds during routine sampling. Detailed necropsy of the six deer revealed a single typical tuberculous lesion in only one, but culturing of various tissue specimens ascertained that the five blood test and comparative cervical skin test-positive animals were all infected. Mycobacterium bovis was cultured from the oropharyngeal tonsils of four and medial retropharyngeal lymph nodes of two of the deer with no typical gross lesions. Six additional tuberculosis-free hinds were introduced to the enclosure in April 1994 and kept there for 12 months. Four of these animals showed a positive lymphocyte transformation assay response to M. bovis after 9 weeks, but no significant reactivity thereafter. Concurrent observational studies suggest that five of the first six deer probably became infected through close inspection and investigation of the tuberculous possums, although the possibility of deer-to-deer transmission cannot be totally excluded. The likely deer-possum contact, and thus exposure to M. bovis, was related to the curiosity and social ranking of the hinds. The second group appear to have had transient exposure to M. bovis, possibly caused by direct contact with the infected hinds introduced earlier. This group never showed any curiosity toward, or interaction with, possums during the periods of observation. 相似文献
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Lugton IW 《Australian veterinary journal》2004,82(6):355-365
OBJECTIVE: To explore the environmental and management risk factors that promote the clinical expression of ovine Johne's disease on farms in New South Wales. DESIGN: Cross-sectional study. PROCEDURE: A questionnaire about the farm, flock and their management was mailed to all farmers known to keep infected sheep in the area zoned residual for ovine Johne's disease in New South Wales. The resultant data were analysed by multivariate statistical methods, specifically examining the factors associated with farmers reporting some mortality due to ovine Johne's disease; the reported annual incidence of ovine Johne's disease-associated mortality; the youngest age at which sheep die from ovine Johne's disease; whether scouring was a feature of the disease; and the season of peak mortality from ovine Johne's disease. RESULTS: Fine wool Merino sheep were more likely to die from ovine Johne's disease than other sheep types. Mortality was higher on farms with light sandy soils and those with a high proportion of improved pastures containing subterranean clover. Winter shearing was also associated with clinical expression. The time that the infection had been present on a farm was not strongly associated with mortality. Higher stocking density, high rainfall and access to open water, factors that are believed to aid transmission, were not found to be influential. CONCLUSION: Clinical expression appears to be principally associated with light infertile soils and their associated pastures and pasture improvement practices which may lead to micronutrient deficiencies or imbalances. Genetic effects are also important and are likely to be exacerbated by physiological stressors, such as winter shearing. 相似文献
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Cattle deaths in two contemporaneous incidents were attributed to acute intoxication with Persicaria lapathifolia and P. orientalis when the plants were under heat and moisture stress. To our knowledge this is the first confirmed report of acute, fatal hepatic necrosis associated with ingestion of these plants. 相似文献
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J Christensen-Dalsgaard W Dappen SV Ajukov ER Anderson HM Antia S Basu VA Baturin G Berthomieu B Chaboyer SM Chitre AN Cox P Demarque J Donatowicz WA Dziembowski M Gabriel DO Gough DB Guenther JA Guzik JW Harvey F Hill G Houdek CA Iglesias AG Kosovichev JW Leibacher P Morel CR Proffitt J Provost J Reiter EJ Rhodes FJ Rogers IW Roxburgh MJ Thompson RK Ulrich 《Science (New York, N.Y.)》1996,272(5266):1286-1292
Data from the Global Oscillation Network Group (GONG) project and other helioseismic experiments provide a test for models of stellar interiors and for the thermodynamic and radiative properties, on which the models depend, of matter under the extreme conditions found in the sun. Current models are in agreement with the helioseismic inferences, which suggests, for example, that the disagreement between the predicted and observed fluxes of neutrinos from the sun is not caused by errors in the models. However, the GONG data reveal subtle errors in the models, such as an excess in sound speed just beneath the convection zone. These discrepancies indicate effects that have so far not been correctly accounted for; for example, it is plausible that the sound-speed differences reflect weak mixing in stellar interiors, of potential importance to the overall evolution of stars and ultimately to estimates of the age of the galaxy based on stellar evolution calculations. 相似文献
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IW Caple 《Australian veterinary journal》2011,89(8):282-288
World Veterinary Year in 2011 celebrates the 250th anniversary of the establishment of the first modern veterinary school at Lyon in France. To put veterinary education in Australia in its historical context, the veterinary school at Lyon was established nine years before the British had discovered the east coast of Australia in 1770, and 27 years before a shipment of convicts transported from overcrowded gaols in England had arrived in Sydney in 1788. This paper discusses the development of veterinary education in Australia from that time to the present day. 相似文献
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