Johne’s Disease: Cattle

Testing

Because Johne's disease is a hidden disease, testing can be a useful part of a management plan. Testing alone, however, is not enough to control or eliminate Johne's; you need management, too. Consult your herd veterinarian to develop a herd testing strategy that is right for you BEFORE you test and then follow your plan.
A few reasons to consider testing:

• Management benefits – By knowing an animal’s test status, you can minimize exposure of susceptible animals.
• Economic benefits – Knowing the test status of herds from which you purchase reduces your risk of buying Johne’s disease. If you sell cattle and your herd is test-negative for Johne’s disease, you may be able to market animals for a premium.
• Legal benefits - You may be liable if you sell an infected or exposed animal as if it were healthy.

Types of Tests

No single test is sufficient for all purposes, but reasonably accurate and cost-effective tests are available for different diagnostic and control needs. Johne’s disease tests are divided into two main types of tests: those that detect antibodies that an animal makes in response to infection (e.g. serum or milk ELISA) and those that detect the bacteria that causes Johne’s disease (e.g. culture or PCR (DNA probe)). Current tests do not identify animals at early stages of infection reliably; therefore, repeated testing is recommended.

Individual animals are tested with any of the options noted above. Producers may also elect to test environmental samples or pool individual samples using the tests that detect bacteria. Both of these testing strategies are effective in determining if the bacteria causing Johne’s is present in a herd. Submitting individually collected samples for the lab to pool may also be a cost effective way to use test results for making management decisions if the herd is not heavily infected.

Test Frequency

This will depend on each herd’s goals and resources. In general, annual testing is recommended, but some herds may wish to test more frequently (eradication) and some herds may elect not to test at all.

Testing for Herd Classification

Some producers may choose to classify their herd, especially if the herd is a low risk for Johne's disease or they are selling animals to other producers.  For more information, see Herd Classification Program.  

Submitting Laboratory Samples 

Your veterinarian can submit samples to any laboratory approved for the Johne’s disease test elected. A list of approved laboratories for specific tests can be found at: http://www.aphis.usda.gov/animal_health/lab_info_services/approved_labs.shtml

It is very important that samples are correctly collected and submitted, with completed paperwork. For producers participating in the Herd Classification Program this is especially important to ensure the herd is appropriately classified.