Surprise diagnosis

A hobby farmer cared for a "closed flock" of 15 ewes. The only herd addition was made 2 years earlier when she bought a ram from a large show flock.

A 2 year old Clun Forest ewe had not been doing well for about 3 months. Her dam and her own lamb were also thin. She had been losing weight, suffered periodic bouts of diarrhea but her appetite was good and she did not have a fever. The farmer was concerned about parasites - in fact "stomach worms" were diagnosed and treated but she did not improve. A fecal culture for M. paratuberculosis was negative. The ewe was segregated from the flock and was euthanized shortly thereafter when she became too weak to stand.

Upon necropsy (term for an autopsy on animals) the Johne's disease diagnosis was confirmed. Pathologic lesions consistent with M. paratuberculosis were found throughout the gastrointestinal tract and the organism was isolated from numerous tissue sites. An AGID test was weakly positive.

The owner slaughtered the dam, ram and lamb. She tested her entire flock by fecal culture - no isolations of M. paratuberculosis were made. No further cases of Johne's disease have appeared in the last 4 years.

Case lessons:

1. In some situations, the source of the infection will never be determined.
2. A negative test result (fecal culture) may not mean that the animal is free of infection.
3. Other health problems may exist in addition to Johne's disease (e.g. parasites).
4. An aggressive test-and-cull approach can control the spread of the infection.