Can Johne’s Disease be eliminated from a herd?
Herd owners who work at eradicating Johne’s Disease from their herds often get frustrated. Is it even possible? Is that the goal?
The natural reaction of many to the presence of a transmissible disease, such as Johne’s Disease (JD), within the herd is to want to eliminate it completely. Many have done exactly that with mastitic diseases such as Staph. aureus or Strep. ag. Not only is there the positive feeling of accomplishment and thrill of victory, but there is a real benefit to eliminating a disease and not having to deal with it.
- But can JD be eliminated? Here are the problems that we know of in that battle.
- The limits of current testing methods for JD mean that more than half of the infected animals may go undetected in a single test.
- Because of that, culling alone will never eliminate the disease.
- While we can reduce the likelihood of disease transmission to calves by management practices, it is difficult to completely eliminate this risk. Plus, there is still a risk of in utero transmission from an infected dam.
- Since JD control requires long-term commitment, inconsistency in efforts to reduce the risk of transmission can occur and this can allow calves to become infected.
The experience of herds in the Michigan JD Control Demonstration Project (MJDCDP) is that elimination is very difficult. One farm involved in this project has taken very aggressive steps to eliminate the disease including rapid removal of calves from dams, isolation of calves from older animals and culling of test-positive cows. Their experience, mirrored somewhat by several other herds in the project, was that on some annual herd tests no JD was detected by one of the two methods (fecal culture or serum ELISA), but that the other test done at the same time and subsequent tests in following years showed positive animals. The take home point is that getting to zero infected animals is difficult.
Yet, we remain confident that with time and consistent efforts to reduce the risk of transmission, it is possible to eliminate the disease. For a herd owner to be sure that the disease is not in their herd, we would recommend that all animals test negative for three consecutive tests and that ideally, both fecal and blood or milk testing be done to confirm the absence of the disease.
However, maybe the question should really be, “Is my JD control program effective?” The battle against JD is not an “all or none” fight. There are benefits to be achieved by reducing the prevalence and the new infections within a herd. All of the herd owners and managers who participated in the MJDCDP saw improved calf health and reduced cow culls due to severe illness. They believe that continuing these practices will lead to continued benefits, even if they don’t completely eliminate the disease.
Control measures by a farm should be applied as they make economic sense for a farm, and they should be applied consistently. This is not to imply that anyone should be content with JD in their herd, but that you should have a realistic view that this will be a long battle with ups and downs but a trend toward fewer and fewer positive animals and fewer signs of the disease. Even that can bring the thrill of victory to a farm battling JD!
For more information on the MJDCDP, visit the MSU College of Veterinary Medicine website.