New Strategies for Johne's Disease Testing
1. What test do I choose for direct detection of the causative agent of Johne's disease?
WADDL recommends Mycobacterium avium subsp. paratuberculosis (MAP) detection be performed using polymerase chain reaction (PCR). A major advantage of the PCR test is that results will usually be available in a week or less compared to months for culture.
2. What samples do I need for PCR?
Feces or intestine should be collected and shipped chilled with a frozen gel pack. PCR has not been validated on other tissues and may be cultured by special request.
3. What other test options are available for Johne’s Disease?
Serology currently plays a role in the control strategies outlined in the USDA's Uniform Methods and Rules ( Cattle Disease Information/Johne's Disease Info) or other published control programs (Collins MT, et al. Consensus recommendations on diagnostic testing for the detection of paratuberculosis in cattle in the United States. JAVMA, 229(12):1912-1919, 2006).
4. What samples do I need for Serology?
- Whole blood in a red top or similar tube
- Whole blood in a serum separator tube.
- Milk - Cattle only.
5. Should I choose PCR or Serology?
The decision to choose PCR or Serology or both is dependent on herd prevalence, biosecurity goals and financial factors. It can be complicated. We recommend you consult with a veterinarian and/or veterinary microbiologist or pathologist for aid in decision making. The following resources may provide helpful background in Johne’s diagnostic approaches.
6. What about testing in sheep and goats?
Johne's disease can be a problem in sheep ( Johne's Sheep FAQ's). Sheep have unique ovine strains which are harder to grow and take much longer – negative results are reported for sheep only after 6 months. Therefore, the direct fecal PCR test significantly reduces time for detection of MAP in sheep. Serology is another option for sheep and would be used similarly to cattle.
Johne's disease can be a problem in goats ( Johne's Goats FAQ's ). The MAP strains in goats may be either the cattle-type strains or the sheep-like strains. When testing strategies include detection of the organism in feces, PCR testing will work well. Again, serology is available for testing in goats.
Please note, sheep and goats tend to shed less organisms than cattle, so that even greater care is needed when interpreting PCR tests and follow-up testing may be needed to determine infection status.
Links to WADDL Johne's tests:
- Collins MT, et al. Consensus recommendations on diagnostic testing for the detection of paratuberculosis in cattle in the United States. JAVMA, 229(12):1912-1919, 2006
Page revised September 2019