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Sheep with clinical Johne’s disease most often look like a poorly fed, unthrifty animal. Although appearing sickly, sheep with Johne’s disease continue eating well. And, in flocks with excellent nutrition and husbandry, even sheep with an advance MAP infection may appear healthy until one day they suddenly get thin.
This photo shows a 4 year-old Royal White/White Dorper cross four months before developing severe clinical signs of Johne’s disease. She is obviously healthy looking and pregnant.
This second photo shows the same animal about the time she was tested for Johne’s disease. This animal was found to be shedding massive numbers of MAP in her feces by PCR on a fecal sample) and was also strongly positive by ELISA (VMRD kit). After necropsy, her intestines and associated lymph nodes were also strongly PCR-positive.
Sheep generally do not develop diarrhea, although the feces may become pasty like dog feces and appear with a “dirty rear end”. Intestinal parasites also can cause weight loss and diarrhea in sheep and should be tested for before considering Johne’s disease. If no parasites are found or animals are on effective parasite control programs, then Johne’s disease is a possible diagnosis and should be tested for, ideally by fecal PCR.
Bottle jaw is the results of malnutrition induced by the MAP infection which leads to low serum protein levels. Serum proteins help animals retain fluid within blood vessels, called oncotic pressure. When serum protein levels get too low, fluid leaks out into the surrounding tissues, called edema. When this edema happens under the jaw it is called submandibular edema – more commonly called “bottle jaw”, as in the sheep pictured to the right. Parasites can also cause bottle jaw and should be ruled out before testing for Johne’s disease.