More vigilance needed to monitor spread of prion disease - Booth Descriptions - Brief Article

AORN Journal,  Jan, 2002  

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To better understand how transmissible spongiform encephalopathies (TSEs), such as scrapie and mad cow disease, "jump" and adapt to new species, researchers at the National Institute of Allergy and Infectious Diseases have examined the process by which scrapie transfers from hamsters to mice. According to an Oct 17, 2001, news release from the institute, researchers first inoculated mice with a strain of hamster scrapie, and then closely monitored the mice for several years. This group of mice never became sick, but scientists found that the scrapie agent may have persisted in these mice at levels too low for standard tests to detect.

Researchers found that although the mice did not carry enough of the scrapie agent to be detected on tests, they did carry enough to reinfect hamsters, who were injected with brain extracts from the infected mice. Although these results do not necessarily apply to other TSEs and other species, researchers suggest that TSEs may be more widespread than originally believed. As a result, researchers call for more sensitive diagnostic tests and more vigilance in monitoring the spread of TSEs.

The study also found that, under the right conditions, scrapie gradually adapted to cause illness in mice during a one- to two-year period. In the original group of infected mice, the scrapie agent never caused illness; however, when the agent was transferred from these mice to other groups of mice, the disease grew stronger, making the newly infected group of mice sick, according to the release. Researchers indicate that the scrapie agent replicated faster in additional groups of mice and became more lethal over time. Researchers also noted that scrapie adapted in the mice in different ways. Incubation periods varied widely, and the disease affected different parts of the mice's brains.

Also known as prion diseases, TSEs include chronic wasting disease in deer and elk and Creutzfeldt-Jakob Disease in humans. The hallmark of TSEs is misshapen protein molecules that clump together and accumulate in brain tissue. These abnormal prion proteins are the likely cause of the brain damage that occurs with TSE diseases. According to the release, scientists believe the misshapen prion proteins somehow induce normal prion proteins to form incorrectly and that these abnormal molecules may spread the disease to other individuals.

Study Examines How Prion Disease Adapts to New Species (news release, Washington, DC: National Institutes of Health, National Institute of Allergy and Infectious Disease, Oct 17, 2001) http://www.nih.gov (accessed 18 Oct 2001).

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