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HISTORY
JOHNE'S INFORMATION CENTER - University of Wisconsin Ñ School of Veterinary Medicine

TRUE CASES & STORIES
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A pygmy goat herd had been managed as the only hoofstock at a farm for 5 years. Kids were born and raised on the premises. Additions to the herd were made from outside sources as well.

Several goats in the herd were thin and diarrhea was noted in these animals on occasion by the owner. One goat was sufficiently debilitated to warrant humane euthanasia. This animal was diagnosed with Johne's disease by histopathology (acid-fast organisms were observed in lesions consistent with M. paratuberculosis infection) and the organism was isolated through culture in a number of the goat's tissues.

As part of a research project, the adult goats in this herd were tested by two Johne's disease tests: fecal culture and the ELISA blood test. At the initial testing screen, positive results were obtained for 12 of 30 goats (40%) from either serum antibody, fecal culture or both assays. Four of these 12 goats produced positive results on both tests and 3 of these animals died within four months of the tests. Johne's disease was confirmed as the cause of death at necropsy for all three.

Of the 18 goats with negative results on both tests, 12 were test-positive by either fecal culture or antibody ELISA for M. paratuberculosis when tested again within 8 months of the initial testing screen. Of the 30 animals therefore, 24 (80%) were test-positive for M. paratuberculosis infection during a one year assessment period.

Case lessons:

1. Pygmy goats are susceptible to infection by M. paratuberculosis.
   
  2. Blood and fecal culture diagnostic assays can effectively be used to determine the prevalence of this disease in a herd.
   
  3. For goat herds with an extensively established infection such as this one, complete depopulation may be the only effective method of eradicating the infection.
   
  4. Efforts to keep this infection out of your herd are much less costly than attempts to control it once it is introduced.


The owners of a conservancy farm (Bull Thistle Farm, WI*) bought three adult Tennessee fainting goats (one buck and two does). They were kept in a pasture with other goats plus another heritage breed (e.g. Jacob sheep) and shared a barn with 60 ewes. The adjoining pen held Highland cattle.

The buck began to lose weight after being on-site for about 18 months. He was wormed for coccidiosis and Parelaphostrongylus tenuis [meningeal worm] infection several times with no response. He developed a rough coat and became increasingly debilitated although his appetite remained good. No diarrhea was observed. The protein in the buck's blood was abnormally low (hypoproteinemia) and when a blood test for Johne's disease was completed (AGID), the result was positive. At necropsy, it was confirmed that the animal was infected by the organism causing Johne's disease (i.e. lesions consistent with the infection were found, an acid-fast staining organism was detected in the tissues and M. paratuberculosis was isolated from multiple tissues through the culture method).

The owners purchased more goats from a different source after they had negative test results by AGID. They kept the kids in the herd which soon grew to 40 animals. Two years later however, the herd was down to four animals. The adults had tested positive by AGID for Johne's disease and were culled along with their offspring. (The owner later learned that, despite her instructions to the auction house that the animals were to be sold for slaughter, they were sold to other breeders).

The owners had tested the adults twice a year to make sure they detected goats as soon as they began to produce antibody to the infection. They no longer keep goats. The sheep flock and the Highland cattle are also tested annually and have remained test negative. These herds are now managed on a "closed" basis.

Case lessons:

1. Tennessee fainting goats can get Johne's disease.
  2. Symptoms of the infection are often thought to be due to parasites.
  3. Diarrhea is not always a symptom of Johne's disease in goats.
  4. You never know what infections may accompany an animal purchased at auction.
  5. This infection can be spread from one species (in this case, goats) to other ruminant species (cattle, sheep). Fortunately, in this case, cross-species transfer did not occur.
  6. It can be years before you learn whether kids/calves/lambs born to infected dams were infected since the infection takes so long to develop. In this case, the owners took the conservative step of culling the offspring of test-positive animals to ensure that the infection was controlled.

*Note: This case has been reported with permission of the owners who encourage all heritage breed managers to be aware of Johne's disease as a possible threat to the health of their animals.