Johne’s disease: A common problem in ruminants

News News | Mar 13, 2021

Johne's disease (pronounced "yo-knees") is a disease problem most producers don't think about much, don't worry about much, because they don't recognize it much. Producers see it a lot more than they recognize it. It is a contagious and eventually fatal disese that presents as a "chronic poor doer." All ruminants are affected by Johne's. The cause is Mycobacterium avium subspecies paratuberculosis, which is a very hardy bacteria that unfortunately persists in the environment for a long time. If you have animals infected with Johne's and they begin to shed the bacteria in their stool, you can expect to have problems long after the shedding animal dies or is removed.

While there is little reliable information on the incidence of Johne's disease in beef cattle, sheep and goat herds, a national study of U.S. dairies found approximately 22% of U.S. dairy farms have at least 10% of the herd infected with Johne's disease. I find that to be a shockingly high incidence of infection, and suggests producers should be aware of and on guard against Johne's disease infection in their herds.

Animals with Johne's disease show weight loss and a normal appetite. Cattle will often present with a persistent diarrhea in the later stages of the disease. Animals with Johne's may exhibit "bottle jaw," or a soft swelling under the jaw, due to protein loss. If the weight loss is very rapid and relatively sudden, affected animals may only survive a short time, a few weeks at best. Even in the advanced stages of Johne's disease, animals may still exhibit a normal appetite, and little or no fever. Diarrhea, though common in cattle in the latter stages of the disease, is not common in sheep or goats.

Usually, infection with Johne's disease occurs fairly early in life. Young animals are considered more susceptible to infection than older, more mature animals. Newborns often become infected with Johne's disease by ingesting small amounts of infected manure from the birthing environment, or from the teats and udder of the dam. It is possible for newborns to be infected while still in the uterus if the dam is infected, or by consuming mycobacterium passed in the colostrum and milk.

Animals infected very early in life with Johne's disease will usually show clinical signs of the disease earlier in life than animals infected later in life. It is thought that the animals that are exposed to and ingest a very large amount of the mycobacterium will show clinical signs earlier than animals that have ingested smaller infective doses.

The economic losses due to Johne's disease can be (and are) very significant. Seed stock producers that sell animals that develop Johne's disease will suffer loss of reputation, and loss of demand for their animals. Commercial producers will suffer losses in production and loss of animals as they lose weight, lose value and die.

Avoid losses due to Johne's by being aware of the clinical signs described above, and investigating the cause of animal loss that exhibits dramatic, unexplained weight loss and a normal appetite. Consult with your veterinarian to determine what is going on, and consider testing to see if you have the problem.

A good testing program for Johne's will use one of the two available tests for detection of the disease. One test uses blood (serum) samples to measure the animal's reaction to the infection; the other test uses a stool sample to detect the organism in the infected animal's feces. Since it is common for affected animals to not mount a detectable response until very late in the progression of the disease, false negatives are common with the blood test. And because infected animals shed the bacteria late in the progression of the disease, and even then only intermittently, false negatives are again common. However, if you test an animal with or without clinical signs of the disease, and the test comes back positive, that would be very significant.

I recommend that if you suspect you have Johne's disease in your herd, either because you have seen the clinical signs or because you have had an animal diagnosed with the disease, you initiate a herd testing program. The goal of such a program is to detect and remove infected animals prior to the animal becoming emaciated, dying and most importantly, before they start shedding the Johne's disease agent in your pastures and lots. Over time, the organism responsible will degenerate and your pastures and lots will "clean up" and your herd will not be exposed to the disease causing agent. Consult with your veterinarian to get started. I find the blood test to be the most informative and less expensive, but both tests can be useful. Again, consult with your vet.

To avoid Johne's in your herd, kids, lambs, and calves should be born in an environment as clean as possible. Avoid contamination of feed and hay with manure by feeding in clean bunks, and not on the ground. Test your herd. Older animals are more likely to test positive than younger animals, so orient testing to older animals.

If you identify positive animals in your herd, you know you have a problem, especially if you raised and did not buy the positive animals. You badly need to get ahead of the problem as soon as possible. Because Johne's infected animals eventually will start shedding mycobacterium in their stool (and in massive amounts), it is absolutely essential to identify and remove those infected animals before they start contaminating the environment, and infecting your future stock.

Johne's disease is much more common than most producers think. If you suspect you have a problem, contact your vet, set up a testing program, and deal with it as soon as possible to avoid future losses.

– The above article provided by Dr. Don Coover, DVM. Along with Dr. Clem Neely, they own and operate SEK Genetics, a cattle and small ruminant reproductive technologies company in Galesburg, Kan., that provides lab services, embryo transfer services, herd health services, and artificial insemination training, services, supplies and semen. Reach them at (620) 763-2211, or at sekgenetics.com.

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