Lymphocyte transformation: an aid in the diagnosis of paratuberculosis
Buergelt, C.D.; Hall, C.E.; Merkal, R.S.; Whitlock, R.H.; Duncan, J.R.
American Journal of Veterinary Research 38(11): 1709-1715
1977
ISSN/ISBN: 0002-9645 PMID: 412443 Document Number: 111504
An evaluation was made of the lymphocyte-transformation test in comparison with currently utilized diagnostic procedures for paratuberculosis, such as direct fecal culture, complement fixation and agar gel immunodiffusion. The lymphocyte-transformation test was conducted with whole blood and with johnin purified protein derivative (PPD), mammalian PPD and avian PPD as antigens. Criterion for a positive test was a stimulation index of .gtoreq. 2.0 to johnin or avian PPD (or both) and exceeding that to mammalian PPD. Ninety animals from 2 bovine herds with paratuberculosis were subjected to the diagnostic tests and later followed to slaughter. Of the 90 animals, 65 were proved infected by results from histopathologic examination or culture of tissue (or both). The direct fecal culture method detected 29% infected slaughtered animals; there were no false-positive, but 44% false-negative results. The complement-fixation test gave 12% true-positive, 2% false-positive and 61% false-negative results, confirming the limitation of this test. The immunodiffusion test yielded 13% true-positive and 60% false-negative, but no false-positive results. The lymphocyte-transformation test accurately confirmed 56% of the animals as positive and gave 16% false-negative and 10% false-positive results, respectively. Using a higher stimulation index decreased the percentage of false-negative reactions, but also the number of the true-positive animals. Positive stimulation indices were seen throughout the spectrum of Mycobacterium paratuberculosis infection. Of animals with advanced clinical paratuberculosis, 3% did not respond on lymphocyte-transformation test. The specificity of immunostimulation in paratuberculosis and other mycobacterial diseases, its diagnostic importance and various factors of interference are discussed.