Long-term strategy: the best way to control Johne’s Disease

Farmers with potential high-risk areas, such as acidic, wet and boggy patches, should fence them off to avoid cattle coming into contact with them.

A three year study into the control of Johne’s, a major wasting disease of cattle, shows it is possible to significantly reduce on farm infection, but often requires a long term, strategic approach to disease control and the commitment of the farmer and his vet.

The findings of the PARABAN project, which involved nine volunteer livestock farms experiencing Johne’s Disease problems, were explained during a final on farm meeting at Glenbervie, Aberdeenshire on Wednesday 3 July.

During the project researchers took 13,000 blood samples, analysed soil and abattoir material and studied farm management systems to discover their role in disease spread. The research was funded by the Scottish Funding Council, in partnership with Scottish Government and industry.

Specialists from the James Hutton Institute, Scotland’s Rural College and the Universities of Glasgow and Edinburgh took part on the project, while industry contributions – some of it in kind – were coordinated by Quality Meat Scotland (QMS). The partners worked with volunteer beef or dairy farmers and their vets, from across Scotland and into Cumbria.

All the herds had suffered problems with Johne’s, which is caused by Mycobacterium avium ssp. paratuberculosis (also known as MAP). Cattle with it develop a thickening of the small intestine and, while apparently eating normally have severe diarrhoea, lose weight and become very thin. Calves become infected by ingesting bacteria from surfaces contaminated with infected dung but the disease has a long incubation period so it is usually several years before the disease takes hold.

“In the three years the number of blood tests showing positive for Johne’s infection dropped by 65%,” said Inverness based Dr Selene Huntley, from SRUC, which led the PARABAN programme. “That is real progress but no-one should believe there is a simple, single solution to tackling this disease. Control frequently requires long term thinking, strategic planning and the determination to carry it through.”

Dr Rupert Hough, research leader in environment, risk and health at the James Hutton Institute, who was also involved in the project, said there was an environmental link to Johne's as the organism can survive in soil which is acidic, has a low organic matter and high levels of iron.

The team from the James Hutton Institute developed a test for viable MAP in soil and sampled high and low risk areas on the PARABAN farms. “We found the organism on 75% of the farms and we also found it where the soil conditions suggested we would. Considering we were looking for a needle in a haystack, these results have given us confidence in the environmental link theory.”

As the farm environment is so varied, the team from the James Hutton Institute also carried out controlled experiments in the laboratory with soils to which MAP was added. These soils were limed to different levels and incubated at 10^oC. Speaking about these results, Dr Hough said: “The initial results from these experiments suggest that on more acidic soils liming reduces the lifespan of MAP, but could cause initial increases of MAP before die-off occurs so cattle clear periods would be required. My advice to farmers with potential high-risk areas, such as acidic, wet and boggy patches, would be to fence them off to avoid cattle coming into contact with them.”

Dr Huntley added: “What is very clear is the need for farmers to gain as much knowledge as they can about Johne’s and potential control measures. We have held a series of roadshow events throughout the programme and 45% of those farmers who attended declared they would change their approach to Johne’s. Reducing infection in the national herd will depend on farmer awareness. We hope the Glenbervie meeting has been another step in that direction.”

Watch the video about the PARABAN project.