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Description and Distribution
In 1917 a disease known as Tyzzer's Disease was described in laboratory mice. In 1946 Errington's Disease was characterized in muskrats in Iowa. In 1971, after considerable experimentation and re-examination, Tyzzer's Disease and Errington's Disease were classified as identical diseases, and because of its earlier description, the disease was called Tyzzer's Disease.
Tyzzer's Disease is a bacterial disease of wildlife and laboratory animals caused by the organism Clostridium piliforme. Tyzzer's Disease has been identified from muskrats in Ontario, Connecticut, British Columbia, Saskatchewan, Iowa, Maryland, Michigan, Wisconsin, Ohio, Oregon, Montana, Idaho, Wyoming and Manitoba; from cottontail rabbits in Maryland; and from numerous types of laboratory animals (rabbits, rats, cats, gerbils, hamsters and rhesus monkeys) worldwide. The disease causes a hemorrhagic cecitis and focal liver necrosis. The causative organism is a pleomorphic, Gram- negative, spore-forming, rod-shaped bacterium.
Transmission and Development
The actual means of transmission has not been determined, but organisms or spores are probably shed in the feces of infected animals. Natural transmission likely occurs through the ingestion of these spores by susceptible individuals from contaminated housing, bedding or feed. The gregarious behavior of muskrats and rabbits increases the likelihood of infection by exposing these species to infected areas. An area which has infected animals present remains contaminated for a considerable length of time.
In muskrats it is believed that the intestinal lesions and death seen with this hemorrhagic disease can occur in 5-10 days following ingestion of contaminated material. Transmission by cannibalism and transplacental infection have been documented in experimental animals. Tyzzer's Disease usually affects young and weanling animals but all ages can be involved. Any stressful factor may predispose the animals to the disease.
Clinical Signs and Pathology
Clinical signs of Tyzzer's Disease are usually few in number because of the acute characteristics of the disease. Signs that may be seen are a profuse diarrhea, melena (the passage of dark-colored, tarry stools due to the presence of blood altered by intestinal secretions), anal bleeding, depression, anorexia and a rough hair coat.
Gross pathological changes include an ulcerative necrotizing colitis and cecitis with extensive hemorrhage and edema, discrete white or yellowish 1-3mm diameter necrotic foci on and in the liver, white streaks within the myocardium, lung congestion, pneumonia and edematous, enlarged mesenteric lymph nodes. The cecum and colon may contain brown fluid fecal material and the cecum may appear dark red-black in color.
Histologically there is epithelial cell necrosis and ulceration in the intestinal tract with necrosis, hemorrhage and edema in the underlying tissues. Liver lesions consist of areas of coagulative necrosis with no inflammatory response. Organisms may be seen in viable hepatocytes along the margin of acute lesions in the liver but these are usually few in number in the muskrat.
Definitive diagnosis of Tyzzer's Disease depends on the histologic demonstration of C. piliforme in the cytoplasm of host cells at the periphery of the necrotic foci on the liver and intestinal tissue. Giemsa, Gomori's methenamine silver and methylene blue stains are the stains of choice. Routine hematoxylin and eosin stain and Gram's stain are of no diagnostic value.
The organism can be cultivated in the yolk sac of embryonated eggs. Fluorescent antibody techniques have also been developed for the diagnosis of Tyzzer's Disease in laboratory animals.
Treatment and Control
Antibiotic sensitivity of the causative organism of Tyzzer's Disease has been highly variable but tetracycline drugs appear to be an effective means of treatment.
No suitable measures exist for the control of Tyzzer's Disease in wildlife species except to remove and dilute the source of infection. This consists of removing lodges and carcasses of dead animals.
Tyzzer's Disease is a potentially significant influencing factor on muskrat and rabbit populations. There have been several die-offs of muskrats in Michigan. It is more significant in younger than in adult animals, and during long periods of stress, mortality is at its highest. Die-offs may occur in either the spring or the fall.
Tyzzer's Disease is not of human health significance.
For questions about wildlife diseases, please contact the Michigan DNR Wildlife Disease Laboratory.
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