Johne's Disease Information
DISEASE AGENT AND TRANSMISSION: Johne's Disease is caused by the bacterial agent, Mycobacterium avium subs. paratuberculosis. This is a hardy organism which survives long term in the environment and has a very long incubation period in the animal before producing clinical disease (2-4 years). An infected animal may not test positive until it has been shedding large numbers of organisms into the environment for quite some time. The bacterial agent is spread primarily through manure, milk and colostrum. This is especially important since young stock (less than 6 months of age) are much more susceptible than older animals.
CLINICAL SIGNS: The agent resides in and invades the intestinal tract and the lymph nodes associated with it. This results in clinical signs of disease related to the intestinal tract, including chronic diarrhea (sometimes severe), wasting of body condition, edema (fluid collection), reduced production and intestinal thickening. These symptoms may only be evident in advanced stages of the disease.
INTERPRETATION OF TEST RESULTS: If all 30 of the cows are negative to the test, the producer can be 85% certain that his herd is free of JD. If some of the tests from the 30 cows are positive, it is quite likely that JD is present in the herd. However, it is recommended that fecal samples be collected, for culture of the JD organism, from those cows testing positive on the serum test. The cows are not considered positive until the organism is grown from the feces (organism detection test). This culture testing would take an additional four months to complete and would currently be done at the producer's initiative and expense.
SUGGESTED MANAGEMENT CHANGES
Don't pool colostrum for calf feeding.
Don't feed milk or waste milk to calves (unless it is pasteurized) - use milk replacer.
Use a different tractor bucket for moving feed than is used to move manure.
Clean off vehicle tires, etc. to prevent contamination of feed with manure.
Don't apply to hay or pasture that will be harvested or grazed that year.
Apply manure to cropland that will be plowed, etc.
Minimize exposure of calves to manure from adult animals.
Separate calves from dams as soon as possible (2-4 hours).
Obtain replacements from a negative herd or a herd classed the same as your herd.
Control access of outside animals, people and vehicles to the farm (biosecurity).
Apply permanent ID to every animal in your herd.
Don't co-mingle with other herds.
Clean out water troughs on a regular basis (depending on contamination rate).
Don't walk in the feedbunk or allow other people or animals to do so.
Don't give feed bunk cleanings from adult cattle to heifers (could give it to feeder steers).
Grazing - don?t follow adults with young stock. Put them in a separate pasture system.