Post by AnnB (NE) on May 15, 2010 0:03:07 GMT -5
Johne’s Disease
Ann B. Bledsoe
Arrowhead Ridge Miniature Jerseys
Ann B. Bledsoe
Arrowhead Ridge Miniature Jerseys
Johne’s (yo-nees) Disease, Mycobacterium Avium Paratuberculosis, most folks have never heard of it. This chronic mycobacterial infection, principally affects the lower small intestine of ruminants. Cattle, sheep, and goats, and less frequently deer, llama, bison, and other ruminants, are all susceptible to the disease.
Left to it’s own devices, this insidious bacterial infectious disease can be widespread in a herd before any animals show clinical signs. Anyone selling breeding stock, be it commercial replacement females, registered seedstock, or recipient females, faces increased liability. Recent court cases underscore the fact that sellers shoulder the responsibility for knowing the Johne’s status of any cattle they sell.
Not seeing symptoms does not mean that animals in your herd don’t have it, it’s easy to miss signs of the disease, unless you investigate whether it’s there, specifically.
Johne’s is usually imported into a herd with an infected animal that is not yet showing signs of the disease. Due to the long incubation (2-10 years), signs of Johne’s Disease typically develop in animals one at a time over a period of years. Cows infected with Johne’s may show no signs of the disease until years after the initial infection. But most will eventually exhibit chronic diarrhea and weight loss while maintaining a good appetite, a decline in milk production is also common. Animals shed the organism and are infective to others before they show the signs of chronic diarrhea and weight loss, while they still appear completely healthy. Most animals first show signs after the stress of calving, with most animals showing signs at 5-7 years of age.
Most animals are infected as calves, soon after birth, by ingesting colostrum from their infected dam or by ingesting manure from an infected animal, either from the dam’s udder or from the environment. Preventing the calves from becoming infected is most important. Manure management also plays a large role in the control and eradication of Johne’s Disease.
There are tests available for Johne’s, but none are foolproof. The antibody tests show both false positives and false negatives. The fecal culture takes a long time and doesn’t detect all animals that are shedding. The fecal PCR is the most accurate at detecting shedding animals, testing for the DNA of the organism, but cannot detect an animal that is not yet shedding the organism. No test will detect an animal that is not yet shedding the organism. It takes several years of testing to be assured that a herd is free of Johne’s Disease.
Due to the limitations of current testing methods, it is much more important to purchase replacement animal from herds that are test-negative, than it is to have a single negative test on any particular animal.
While Johne’s can be widespread before being detected, it can be eradicated. The most important thing a producer can do is to learn more about the disease, how it can impact their individual operation, and how they can reduce risk of infection. The longer a producer waits to identify Johne’s in the herd, the more opportunity it has to spread.
For further information on Johne’s Disease visit www.Johnes.org. Contact your vet for information on Johne’s testing as well as Johne’s Risk Assessment and Johne’s Prevention Protocols that will work for your farm.