EVALUATION OF AN AGAR-GEL IMMUNODIFFUSION TEST KIT FOR DETECTION OF ANTIBODIES TO MYCOBACTERIUM-PARATUBERCULOSIS IN SHEEP

Objective-To determine whether a commercially available agar gel immun odiffusion test approved for detecting antibodies to Mycobacterium par atuberculosis in cattle could be used for sheep. Design-Experimental t rial. Sample Population-Serum samples from 27 sheep confirmed to have paratuberculosis by means of acid-fast staining of smears of ileal muc osa, histologic examination of tissues, or bacteriologic culture; 7 sh eep with clinical signs of paratuberculosis; and 55 sheep from 5 uninf ected flocks. Procedure-Serum samples were tested concurrently with th e commercially available test and with a previously validated agar gel immunodiffusion lest. Multiple samples collected from 13 infected she ep over a period of 6 years were also tested so that each test's abili ty to detect onset of seropositivity could be compared. Results-For bo th tests, results for samples from all 55 uninfected sheep were negati ve, results for samples from 32 of the 34 sheep with paratuberculosis were positive, and results for the remaining 2 sheep with paratubercul osis were negative. Results of both tests were in agreement for 50 of 54 samples obtained from 13 infected sheep over time. The 4 samples fo r which results of the 2 tests disagreed were the fourth, eighth, and ninth of 10 samples from 1 sheep and the first of 6 samples from a sec ond sheep. For all 4 samples, he commercially available assay yielded a weak-positive result, but the previously described test yielded a ne gative result. Clinical Implications-The commercially available agar g el immunodiffusion test approved for use in cattle may be useful in th e differential diagnosis of paratuberculosis in sheep.