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Study: Deer May Spread Brain Disease Through Feces

Posted on: Thursday, 10 September 2009, 07:38 CDT

According to a study published on Wednesday, it appears that a variety of prion disease found in deer may be spread through the fecal matter of infected animals even when they exhibit no symptoms of the illness. 

Researchers say that their finds on the deadly brain disorder known as chronic wasting disease (CWD)—a close cousin of the infamous mad-cow disease—may have significant ramifications for farmers.

The research was led by Nobel laureate Stanley Prusiner at the University of California, whose previous award-winning work elucidated how the disease is brought on by mis-folded proteins which eventually lead to degenerate neural tissue.

Other well-known varieties of prion disease include the bovine spongiform encephalopathy (BSE) in cattle, scrapie in goats and sheep, and Creutzfeldt-Jakob disease (CJD) in humans.

It has been well-known for years that the deer-related version, CWD, is inherited by offspring from their mother.  But Prusiner’s research, published in the most recent edition of Nature, has shown that deer may also be able to contract the disease by consuming remnants of feces in the soil when they graze.

Prusiner’s research team started their study by orally infecting five mule deer with CWD prions.  Samples were then regularly taken from the animals until they either died or were euthanized after developing symptoms of the disease.

Researchers then irradiated samples of feces from the deer—a process that destroys bacteria and viruses but leaves the defective proteins unaffected—and injected them directly into the brains of lab mice.

Control samples taken from the deer before they were infected produced no observable changes in the mice, while more than 90 percent of the samples taken from the deer after infection caused the mice to develop CWD-like symptoms.

Prusiner’s team say that their results clearly point to a “horizontal” pathway of infection that may also hold true for scrapie, the closely-related sheep and goat version of the disease.

A 1994 study conducted in Iceland first lent credibility to the “fecal-oral route” theory, when a group of scientists held a flock of scrapie-infected sheep in a field and then later introduced a scrapie-free flock, which eventually developed the disease without coming into direct contact with the first flock.

Scientists have as yet, however, been unable to figure out just how long the prion pathogens can survive in the soil before they’re degraded by harsh weather and bacteria in the soil.

There is currently no known relationship between CWD and any other forms of transmissible spongiform encephalopathy (TSE) such as BSE, which unleashed the mad-cow disease scare in the late 1990s.  Although there have been media reports of humans being infected with CWD, a 2004 study conducted by the U.S. Centers for Disease Control and Prevention found no connection between the two diseases.

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On the Net:

• University of California
• Nature

Source: RedOrbit Staff & Wire Reports

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