BJD Testing

Animals are tested in two stages - screening tests of large numbers and follow-up tests of reactors. Tests detect the bacteria itself or the body's response to its presence.

There are two types of screening test available to test for BJD in live animals.

1. Antibody tests (blood tests)

The main antibody test (serological or blood test) for BJD is the absorbed ELISA test in cattle. There is also a Gel or AGID test used for goats. In the Market Assurance Program the number of animals sampled is determined by the size of the herd. Blood samples are collected from all animals, or an appropriate sample of animals within a herd. The blood test detects antibodies to the Johne's disease bacteria and results are reported relatively quickly (one or two weeks).

2. Faecal culture

Dung or faecal samples collected from individual animals are cultured for the bacteria. This is more expensive and slower than serology, taking from two to five months, depending on the culture method used.

As there are no serological tests approved for alpaca and deer, faecal culture is the test of choice in these species. It is also used as a definitive test to confirm infection in cattle that react to the ELISA and can be used together with serology in cattle herds to increase the chance of detecting infected animals.

Follow-up Tests

Any animals or groups of animals that test positive to an antibody-screening test are tested again with a definitive test to confirm the result. For instance, ELISA reactors are tested by individual faecal culture or by a post-mortem examination, microscopic examination of the gut tissue and possibly culture of gut tissue. These tests detect the bacteria itself or the characteristic microscopic lesions that it causes.

Page Updated: 1 July 2005