Johne's Disease in Goats

Johne’s Disease in Goats 3

Johne’s (“YO-knees”) disease is a fatal gastrointestinal Lymphadenitis (CLA) and Caprine Arthritis-Encephalitis Virus Q: Why do goats with clinical signs of Johne’s disease disease of goats and other ruminants (including cattle, (CAEV)—laboratory tests are needed to confirm a diagnosis.lose weight and become weak? sheep, elk, deer, and bison) that is caused by the bacterium Mycobacterium avium subspecies paratuberculosis (MAP). When an animal with signs of Johne’s disease is discovered, it is very likely that other infected animals—even those A: When an animal is infected with MAP, the bacteria reside in Also known as paratuberculosis, this infection is contagious, that still appear healthy— are in the herd. Control of the the last part of the small intestine—the ileum—and the intestinal lymph nodes. At some point, the infection progresses as bacteria multiply and which means it can spread in your herd. infection requires that you and your veterinarian address it in take over more and more of the tissue. The goat’s immune system

The MAP organism is most commonly passed in the ma- the whole herd and not just on an individualresponds to the bacteria with inflammation that thickens the intestinal nure of infected animals. The infection usually spreads from animal basis. wall and prevents it from absorbing nutrients. As a result, a goat in the adult goats to kids and occurs when a young animal swallows When an animal is infected with MAP, the bacteria reside clinically ill stage of Johne’s disease in effect starves to death. At this the organism via water, milk or feed that has been contam- in the last part of the small intestine—the ileum—and the stage the organism may also spread beyond the gastrointestinal tract, inated by manure from infected animals. Most owners are intestinal lymph nodes. At some point, the infection protravelling in the blood to muscles or other major organs such as the liver or lungs. taken by surprise when the infection is diagnosed, and learn gresses as bacteria multiply and take over more and more of too late that the infection has the tissue. The goat’s taken hold in multiple animals immune system rein a herd. sponds to the bacteria

Due to lack of testing and with inflammation that reporting, it is not known how thickens the intestinal widespread Johne’s disease is wall and prevents it in goats in the United States. from absorbing nutriThe infection has been con- ents. As a result, a goat firmed, however, in many goat in the clinically ill stage herds throughout the coun- of Johne’s disease try—in milk, meat, heritage in effect starves to and other breeds—and it death. At this stage is a problem in most other the organism may also goat-rearing countries as well. spread beyond the The costs of this infection Top: Thickened intestinal mucosa caused by Johne’s disease. gastrointestinal tract, range from economic losses— travelling in the blood due to reduced production and Bottom: Thin, pliable, normal intestine to muscles or other increased culling for meat and major organs such as milk animals—to emotional losses—for those whose goats the liver or lungs. are more pets than agricultural investments. Since there is no cure for Johne’s disease, control of the

There is no cure for Johne’s disease, and there is not infection is critical. Control of Johne’s disease takes time and anapproved vaccine for goats in the United States to help a strong commitment to management practices focused on protect them rom infection. Therefore, prevention is the key keeping young animals away from contaminated manure, to control. milk, feed and water. A typical herd clean-up program may

A goat that appears perfectly healthy can be infected take a number of years. The basics of control are simple: new with MAP. Although goats become infected in the first infections must be prevented, and animals with the infection few months of life, many remain free of clinical illness until must be identified and removed from the herd. months or years later. When goats finally do become ill, the Your State Designated Johne’s Coordinator can help you symptoms are vague and similar to other ailments: rapid undertake an on-farm risk assessment that evaluates your weight loss and, in some cases, diarrhea. Despite continuing operation, your resources and your goals. to eat well, infected goat soon become emaciated and weak. The University of Wisconsin School of Veterinary Med-

Since the signs of Johne’s disease are similar to those for icine’s Johne’s disease website—www.johnes.org—adseveral other diseases— parasitism, dental disease, Caseous dresses all aspects of Johne’s disease for multiple species,

including goats. The site has an “Ask An Expert” feature that allows you to submit your own questions and receive a personalized response from an expert. The University of Wisconsin School of Veterinary Medicine also offers a free online course for goat producers. Simply go to www.vetmedce.org, click on “Courses” in the lower left hand corner of the homepage. Once on a new page, click on “Johne’s Disease.” At the next new page, click on “Johne’s Disease Courses for Producers” followed by clicking on “0017—Johne’s Disease for Goat Producers.” To learn more about Johne’s disease in goats, please contact your State animal health regulatory agency or your State Designated Johne’s Coordinator. Contact information for your State’s Johne’s diseas program is available online at www.johnesdisease.org when you click on “State Contacts.”

Additional information and resources available at http://www.johnes.org/. Information reprinted with permission by Michael T. Collins, DVM, PhD, DACVM, Johne’s Testing and Information Center, School of Veterinary Medicine, University of Wisconsin-Madison.

How Do You Control Johne's Disease in a Goat Heard?

The best methods for MAP infection control in your goat herd depend on the resources available, the goals of your enterprise, and the methods you use to take care of your goats. All control methods however rely on two core strategies that must be employed at the same time: Kids must be protected from infection by being born and raised in a clean environment and fed milk and water free of MAP contamination. The primary sources of MAP contamination are manure and/or milk from infected adult animals. Adult animals infected with MAP must be identified and culled managed to ensure no kids are exposed to their milk or manure. Because twins are common for goats, the annual risk of a new case born to an infected doe is believed to be twice the risk seen in species that produce just one offspring a year. No vaccines are available in the United States for Johne’s disease in goats, however, in Spain, Australia and several other countries vaccines are used.

What are the symptoms of Johne's Disease and what causes them?

There really are only two clinical signs of Johne’s disease: rapid weight loss and diarrhea. In goats, diarrhea is less common than in cattle. The MAP infection occurs in kids in the first months of life, but signs of disease usually do not appear until the animals are adults. Despite continuing to eat well, adult goats become emaciated and weak. Since the signs of Johne’s disease are similar to those for several other diseases, laboratory tests are needed to confirm a diagnosis. If a case of Johne’s disease occurs, it is very likely that other MAP-infected goats, that may still appear healthy but are incubating the infection, are in the herd. No one yet understands what causes a clinically normal goat that has been infected by MAP for months or years to suddenly become sick from the infection.We do know that at some point the MAP that have been lying quietly within cells of the last section of the small intestine (called the ileum) start to replicate and take over more and more of the tissue. The animal’s immune system responds to all these organisms with what is called granulomatous inflammation. This inflammation thickens the intestinal wall, preventing it from functioning normally. This, among other factors, means the animal cannot absorb the nutrition it needs and thus begins to lose body condition, milk production drops off, and diarrhea may occur. In effect, an animal with Johne’s disease is starving in spite of having a good appetite and eating well.

How do Goats Get Infected?

Johne’s disease typically enters a herd when a MAP-infected, but healthy-looking, goat is purchased. This infected goat then sheds MAP in its feces onto the premises – perhaps onto pasture or into water shared by its new herdmates. Young animals are far more susceptible to infection than are adults: these kids swallow the organism along with grass or water. Perhaps they are bottle-fed with MAP-contaminated milk collected from the infected but healthy-appearing new arrival. Milk may become contaminated from the environment (manure-stained teats) or, in the advanced stages of the infection, the bacterium is shed directly into the milk. Animals may even have been infected before they are born, called in utero transmission, if the doe is in advanced stages of the MAP infection. Thus the infection spreads insidiously,