Dairy Event 2009: Better testing for Johnes needed, says vet

Johnes control should no longer rely on testing and culling, but should involve a comprehensive test and management program, said vet Pete Orpin, speaking at a Farm Health Planning Demonstration at this week’s Dairy Event and Livestock Show.

“Half of dairy herds are infected with Johnes within the UK, with 5-10% having a significant problem.”

We need to dispel the myth that disease is something we have to live with, said Ben Bartlett from National Milk Laboratories (NML).

“For many, managing disease involves doing nothing and living with the problem or testing and culling infected animals. The problem with test and cull is it does not deal with prevalence.”

“The question is, how can we tackle disease in a proactive manner?”

We need to establish the risk of disease spread from one farm to another and spread within the herd, said vet, Dick Sibley.

Johnes disease is picked up in young calves, with 80% of infection occurring in the first month. “The key to control is preventing calves from being exposed.”

And when disease status is continually monitored, a farmer will be well equipped to stop disease spread.

Milk should be regularly tested to establish the status of your herd, said Mr Sibley. “Herdwise, from NML, uses a traffic light system to categorise individual animals according to their likelihood of spreading or developing the disease.”

Any red or amber animals can be identified and selected to calve in isolation in a ‘leper colony’, so disease does not enter young calves, Mr Orpin continued.

“Cows should be regularly tested and, if any develop clinical signs of the disease, they should be culled. Also, ensure waste milk from these cows is not fed to calves. This forms the basis of your test-and-manage programme.”

“By intensively managing 10-15% of your herd, you are preventing Johnes from entering young stock,” he said.

Eventually these high-risk cows will die and the herd health status will be restored.