Evaluation of diagnostic tests for Johne's disease in young cattle

• Published in: Australian veterinary journal Vol. 77; no. 2; pp. 113 - 119
• Main Authors: McDonald, W.L, Ridge, S.E, Hope, A.F, Condron, R.J
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.02.1999
• Subjects: absorbed EIA; Animals; Bacterial Vaccines - immunology; calf; calves; Cattle; Cattle Diseases - diagnosis; Cattle Diseases - prevention & control; culture; culture techniques; diagnostic techniques; enzyme immunoassays; feces; Feces - microbiology; Female; Histocytochemistry; IFN-g EIA; immune response; Immunoenzyme Techniques - veterinary; Interferon-gamma - blood; interferons; Johne's disease; Mycobacterium avium subsp. paratuberculosis; Mycobacterium avium subsp. paratuberculosis - immunology; Mycobacterium paratuberculosis; paratuberculosis; Paratuberculosis - diagnosis; Paratuberculosis - prevention & control; Polymerase Chain Reaction - veterinary; Vaccination - veterinary
• ISSN: 0005-0423; 1751-0813
• DOI: 10.1111/j.1751-0813.1999.tb11679.x

Objective To investigate the development of immune responses in calves experimentally and naturally infected with Mycobacterium paratuberculosis and to evaluate the potential for diagnostic tests to detect infected calves. Design Sequential testing of four treatment groups of calves over a 2 year period. Procedure Twenty‐nine calves were allocated to four groups. Group D calves were orally dosed with M paratuberculosis, group N calves naturally exposed to M paratuberculosis, group V calves vaccinated for M paratuberculosis, and group C were control calves (not infected or vaccinated). Blood and faecal specimens were collected from each calf at monthly intervals to 18 months of age and then every 2 months until they were slaughtered between the ages of 21 and 29 months. Specimens were tested using absorbed EIA, IFN‐g EIA and faecal culture. The infection status of the calves was confirmed by extensive histopathological examination and tissue culture. Results M paratuberculosis infection was confirmed in 10 calves, comprising six of eight orally dosed calves, three of five naturally exposed calves and one of nine vaccinated calves. The six artificially infected calves and one naturally infected calf were detected shedding M paratuberculosisi n their faeces. Results with positive absorbed EIA were obtained from one artificially infected calf, one naturally infected calf and three vaccinated calves. All calves including controls had positive results on at least one occasion using the IFN‐g EIA. In addition, seven calves had positive bovine tuberculosis results using the IFN‐g EIA, even though bovine tuberculosis has been eradicated from Australia. Conclusion Detection of M paratuberculosis infection in young cattle continues to be difficult using current tests.