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Epidemiologic and experimental studies on transmissible mink encephalopathy
1Department of Animal Health and Biomedical Sciences, University of Wisconsin-Madison 53706.
Abstract:
Transmissible mink encephalopathy (TME) is a rare foodborne disease of ranch-raised mink produced by an as yet unidentified contaminated feed ingredient. Because of the clinicopathologic similarities to scrapie and the indistinguishable physicochemical properties of their transmissible agents, it was initially assumed that TME was caused by feeding mink scrapie-infected sheep. However, subsequent studies testing the oral susceptibility of mink to scrapie were unsuccessful. Epidemiologic investigations of individual incidents of TME have not identified an association between the occurrence of disease and the feeding of any particular ingredient. However, there are two incidents in which the rancher was confident that sheep were not fed. The most recent of these was in Stetsonville, Wisconsin in 1985 where the meat portion of the diet was composed almost exclusively of downer dairy cows. To examine the possibility that cattle may have been the source of infection on the Stetsonville ranch, mink brain was experimentally inoculated intracerebrally into two Holstein steers. Both of these animals developed fatal spongiform encephalopathies 18 and 19 months after inoculation. These findings are compatible with the Stetsonville incident of TME being caused by feeding mink infected cattle tissue and they suggest the presence of an unrecognized BSE-like disease in the United States. Further experimental studies on the Stetsonville source of TME have identified two distinct strains of the transmissible agent in Syrian hamsters. These strains vary in length of incubation period, clinical signs, endstage brain infectivity titre, and pathogenicity for mink.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Transmissible mink encephalopathy (TME) may stem from cattle, not sheep. Experimental inoculation of mink brain into cattle caused fatal spongiform encephalopathies, suggesting an unrecognized BSE-like disease in the US.
Area of Science:
- Veterinary Medicine
- Neuroscience
- Foodborne Illness
Background:
- Transmissible mink encephalopathy (TME) is a rare foodborne disease affecting ranch-raised mink.
- The cause of TME has been elusive, with initial theories pointing to scrapie-infected sheep, but subsequent research has not supported this.
- Epidemiological investigations have failed to link TME outbreaks to specific feed ingredients.
Purpose of the Study:
- To investigate the potential role of cattle as the source of TME in a specific outbreak in Stetsonville, Wisconsin.
- To experimentally determine if cattle can be infected with the TME agent.
- To characterize strains of the TME agent.
Main Methods:
- Experimental intracerebral inoculation of mink brain material into Holstein steers.
- Observation of clinical signs and development of spongiform encephalopathies in inoculated cattle.
- Experimental inoculation of the Stetsonville TME agent into Syrian hamsters to identify and characterize strains.
Main Results:
- Both inoculated Holstein steers developed fatal spongiform encephalopathies 18 and 19 months post-inoculation.
- The findings suggest that cattle infected with a BSE-like disease could be the source of TME.
- Two distinct strains of the TME transmissible agent were identified in Syrian hamsters, differing in incubation period, clinical signs, and pathogenicity.
Conclusions:
- Cattle infected with an unrecognized BSE-like disease may be the source of Transmissible Mink Encephalopathy.
- The study provides evidence for a novel animal prion disease in the United States.
- Further research is needed to understand the prevalence and characteristics of this cattle-associated prion disease.