Three assays for the specific detection of Mycobacterium paratuberculosis by dot spot hybridization of polymerase chain reaction products were applied to fecal samples of dairy cattle. The first two tests used polymerase chain reaction primers and a DNA probe derived from M. paratuberculosis-specific sequences of the 16S rRNA gene and insertion element IS900, respectively. These two tests were carried out on spiked fecal samples to determine the detection limits. The 16S rRNA test was able to detect 107 bacteria per g of feces, and the IS900 test detected 104 to 105 per g of feces. Next, we studied the usefulness of these tests in a control program for paratuberculosis. Therefore, the tests and a third, commercially available, test (IDEXX Corp.) were used twice with an interval of 3 months on fecal samples of 87 cows from two dairy herds with a history of Johne's disease. We compared the results of these tests with those of culturing. This showed that the tests are specific but that the sensitivity ranged from 3 to 23%. Further improvement of the sensitivity is needed before the tests can be used in a control program to eradicate Johne's disease. Mycobactenum paratuberculosis is the etiologic agent of Johne's disease, a chronic inflammatory bowel syndrome in ruminants. The disease has been known for almost 100
Paratuberculosis was diagnosed in one 18-month-old and two 30-month-old hinds in a herd of 70 red deer (Cervus elaphus) in Ireland. Loss of condition and intermittent diarrhoea were the main clinical findings. Clumps of acid-fast organisms were found in the faeces of the three deer. Post mortem examination of one deer showed a slight swelling and pallor of the intestinal tract and associated lymph nodes. Histopathology showed a severe, granulomatous enteritis and lymphadenitis, with extensive cellular infiltration, notably with epithelioid macrophages containing numerous acid-fast organisms. Mycobacterium paratuberculosis was isolated from intestinal and lymph node samples. Paratuberculosis was also confirmed in one of nine clinically normal, yearling stags, sampled at slaughter. Complement fixation tests and enzyme-linked immunosorbent assays gave higher readings for clinically affected deer than healthy ones. Acid soil on the farm was believed to be a contributory cause.
The three Apx toxins of Actinobacillus pleuropneumoniae have potential value for use in vaccines and diagnostic tests which will be species specific instead of serotype specific, provided that the Apx toxins are species specific and all field strains produce these toxins. We examined 114 A. pleuropneumoniae field strains and found that they secreted either ApxI, ApxII, ApxI and ApxII, or ApxII and ApxIII and secreted no other cytolytic activities. However, proteins similar to ApxI and ApxII were also produced by Actinobacillus suis.
Mycobacterium avium was isolated from 82 of 11,664 birds submitted for necropsy in The Netherlands. All isolated M. avium strains belonged to serotype 1, 2 or 3. The greatest number M. avium were from buzzards and falcons. The prevalence of tuberculosis in gulls is extremely low.
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