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JOHNE'S INFORMATION CENTER - University of Wisconsin Ñ School of Veterinary Medicine

Thursday, May 17, 2018
Johne's disease control: a challenging yet achievable goal.

This commentary summarizes the article by Gavin et al. regarding successful eradication of Johne’s disease from a goat herd, mentioned previously on this website. The author, Sam Strain, highlights these key strategies:

Biosecurity Reducing the risk of infection introduction Avoid animal introductions; if introducing animals, ensure the vendor herd has a high Johne’s disease health status; and avoid the introduction of faeces from adults or faecal contaminated materials.

Biocontainment: Reducing the risk of infection spread within the infected herd Identify and remove all ‘high risk’ animals from maternity and young stock areas; ensure colostrum/milk from positive animals is not fed to animals that will be retained for breeding purposes; ensure excellent hygiene standards in maternity areas; prevent cross suckling or consumption of colostrum/milk from multiple dams; and as far as possible keep young stock separate from all adult animals and their faeces.

Testing: Use tests as a management tool to identify higher risk animals; test all adult animals by ELISA (blood or milk), poor sensitivity can, to some extent, be overcome by repeated testing (in general, higher ELISA readings are suggestive of higher risk animals); ELISA test specificity of 98 to 99 per cent will mean that false-positive results will occur; cull or manage high risk animals to avoid infection transmission to young livestock; faecal culture or PCR are useful ancillary tests to confirm infection and to identify higher shedding animals. Animals living in an infected environment can ingest Map or Map DNA without becoming infected – this ‘pass-through’ can be detected in faeces; therefore, care should be exercised in interpreting faecal test results in the absence of ELISA testing.

Comment: In the experience of the author of this website, PCR on fecal samples is superior to ELISA on blood samples, provided the herd infection rate is low. And for herd surveillance, when the infection rate is very low or zero, PCR on fecal samples pooled by age (5/pool) at the testing laboratory is the most cost-effective diagnostic tool.

Two page commentary in Veterinary Record