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Experimental infection model for Johne's disease in sheep
D J Begg1, R O'brien, C G Mackintosh
1Department of Microbiology and Immunology, University of Otago, P. O. Box 56, Dunedin, New Zealand.
Infection and Immunity
|August 23, 2005
Summary
Researchers identified optimal conditions for inducing Johne
Area of Science:
- Veterinary Microbiology
- Ruminant Pathology
Background:
- Johne's disease causes chronic enteritis in ruminants.
- It is caused by Mycobacterium avium subsp. paratuberculosis (MAP).
Purpose of the Study:
- To determine optimal conditions for inducing Johne's disease in sheep.
- To establish predictable infection levels, gut lesions, and clinical signs post-challenge.
Main Methods:
- Two MAP strains (JD3 and W) were tested with varying doses and routes.
- Sheep were orally or intratonsillar challenged with different MAP preparations.
- Infection rates, gut histopathology, and clinical signs were monitored.
Main Results:
- A primary tissue homogenate of MAP strain JD3 yielded high infection rates (90%).
- Oral inoculation of 3-month-old lambs with four doses (5 x 10^8 CFU) of JD3 was optimal.
- Consistent gut histopathology occurred at 9 months, with clinical disease by 11 months post-challenge.
Conclusions:
- Oral challenge with a specific MAP isolate and dosage effectively models Johne's disease in sheep.
- This model allows for predictable study of disease progression and intervention strategies.