LABORATORY DIAGNOSIS OF BOVINE TUBERCULOSIS

Lesions of suspected bovine tuberculosis were examined by culture, histopathology and auramine-O (AO) stained smears and the findings correlated with field aspects of the disease. Of 642 lesions considered to be tuberculous, 62.0% yielded M. bovis and 4.5% other mycobacteria (OM). M. bovis and OM were recovered also from 0.6% and 3.6% respectively of 165 cattle which gave tuberculin reactions but had no visible lesions at slaughter. Of 262 lesions in which a histopathological diagnosis other than tuberculosis was made, 1.5% and 3.0% yielded M. bovis and OM respectively. All OM isolates tested belonged to the Mycobacterium-avium-intracellulare-scrofulaceum (MAIS) complex with a predominance of serotype 2. A good relationship was found between the recovery of mycobacteria and histopathology but examination of smears revealed 22.0% apparent false negatives. Apparent false negative culture results were also reported for 35.8% of lesions positive on histopathology and smear examination. The majority of herds yielding M. bovis contained reactors to the tuberculin test and many of these had lesions of tuberculosis. In contrast, herds yielding OM seldom contained reactors to the tuberculin test and rarely reactors with tuberculous lesions. The thoracic cavity was the main site of lesions from infections by M. bovis and OM.     

SEROLOGICAL RESPONSES IN EXPERIMENTAL BOVINE TUBERCULOSIS

Five two-year-old heifers were each inoculated intravenously with 0.02 mg M. bovis strain AN5. Clinical, haematological and microbiological observations were made during the course of the experiment and antibody levels were measured before and after infection by means of the indirect immunofluorescent antibody (IFA) and bentonite flocculation tests. All cattle developed M. bovis infection varying in severity from peracute tuberculous pneumonia resulting in death within 33 days to chronic progressive generalised tuberculosis. Only cattle developing peracute or acute forms of tuberculosis showed marked haematological changes characterised by leucopenia with lymphopenia. Bacteraemia was detected in the two cattle with peracute tuberculosis 22 days after infection. Anti-mycobacterial antibody was detected after infection in all cattle but fluctuated markedly during the course of the disease. Of a total of 61 serum samples examined from all cattle after inoculation with M. bovis, only 38 were positive to the IFA test and 30 to the bentonite flocculation test. Only 18 were positive to both tests at any one time. IgM was the predominant type of anti-mycobacterial antibody detected by the IFA test and this was found to cross-react with M. avium in almost every sample.     

THE USE OF BOVINE PPD TUBERCULIN IN THE SINGLE CAUDAL FOLD TEST TO DETECT TUBERCULOSIS IN BEEF CATTLE

SUMMARY The efficiency of 2 different doses of bovine PPD tuberculin was compared using the caudal fold test for the detection of tuberculosis in beef cattle. Two matched groups of 98 cattle were selected on the basis of their reactivity to HCSM tuberculin. Cattle in each group were tested with a single 0.1 ml dose of bovine PPD tuberculin containing either 0.1 mg or 0.2 mg bovine PPD respectively. Two further groups of 100 young stock from a herd with an incidence of tuberculosis of less than 0.1% were selected as controls. Tests were interpreted subjectively by palpation and observation and objectively by caliper measurement at 48, 72 and 96 h. All cattle were examined post mortem for the presence of visible lesions.     

双抗夹心—ELISA诊断牛隐孢子虫病

为了建立双抗体夹心—ＥＬＩＳＡ检测牛粪便中隐孢子虫卵囊抗原的方法。采用抗小球隐孢子虫（Ｃ．ｐａｒｖｕｍ）卵囊壁单克隆抗体,经对６０头份牛粪便样本分别进行抗酸染色和双抗夹心—ＥＬＩＳＡ检测,结果抗酸染色法检出１２头份有隐孢子虫卵囊,而ＥＬＩＳＡ除对抗酸染色阳性的１２份粪样判为阳性外,还对抗酸染色阴性的４份粪样判为阳性,且不与牛球虫、牛结肠小袋纤毛虫发生类属反应。此外,本试验在稀释液中加入ＥＤＴＡ,并增加了反应温度,使得试验在抗体包被板并封闭后３０ｍｉｎ结束整个检测过程。结果表明,双抗体夹心—ＥＬＩＳＡ是敏感性高、特异性强的诊断牛隐孢子虫病的方法。