Possible Causes of Chronic Wasting Disease Discovered

According to this story, Dr. Janne Drisko, a physician, treated a patient with a fatal human brain degeneration that’s closely related to the mysterious mad-cow and chronic wasting diseases.

Her patient died in 2000. But the woman’s life had been prolonged by heavy doses of antioxidants – vitamins that reduce inflammation. Drisko didn’t know why, and she worried about the unknowns.

“Until these diseases are fully understood, there’s no telling what is going to happen,” Drisko said. “If you’re not looking for the true causative agent, then it’s a missed opportunity to stop and eradicate the disease.”

Her search for clues led to the Spiroplasma bacterium. Spiroplasma is a corkscrewing filament with no cell wall. But it has a tough cholesterol coating and the ability to survive extreme conditions that kill other bacteria.

Her patient died from Creutzfeldt-Jakob disease, and she found the characteristics of Spiroplasma parallel the characteristics of that disease.

The bacterium’s toughness and tendencies, she said, also make it a candidate for causing other transmissible spongiform encephalopathies such as mad cow in cattle, scrapie in sheep, and chronic wasting disease (CWD) in deer and elk.

So Drisko joined forces with Frank O. Bastian, a Tulane University neuropathologist who has repeatedly linked the bacterium to the diseases. Over the last year, Drisko arranged for brain samples from elk and deer with chronic wasting disease to be sent to Tulane.

In July, Drisko veered from a family vacation to visit a Colorado elk ranch infected with chronic wasting. She’s collecting feed samples and planning to collect insects for Bastian to test for Spiroplasma.

Chronic wasting is not thought to afflict humans. But science once thought the same about the mad-cow disease outbreak in Britain, which killed more than 100 people in 2001 and hammered the nation’s beef industry.

Confusion about the disease causes Spiroplasma to be overlooked as a possible cause, Drisko said. The bacterium, which causes corn stunt and other plant diseases, wasn’t identified by science until the early 1970s.

In the late 70s, Bastian used an electron microscope and found Spiroplasma in brain tissue from a Creutzfeldt-Jakob patient. Later he injected the bacterium into mice and produced a spongiform disease. Research involving proteins and antibodies showed other links.

In recent years, Bastian found Spiroplasma DNA in diseased brain tissue. But he did not find any in disease-free controls. Last year he published the work in a peer-reviewed medical journal.

“If I’m able to show Spiroplasma consistently in these diseases and not in the controls,” Bastian said, “its presence would be a useful marker for the disease.”

But his work remains unknown outside microbiology circles.

Another theory has landed all the publicity and most of the research dollars since the mid-1980s. That theory is that cellular proteins called prions mutate into abnormal forms, killing tissues. This is thought to occur without the direction of a genetic code. Prion theory replaced an earlier leading theory that viruses slow to emerge caused the spongiform diseases. But prion research has not found cures or definitive proof that they cause the diseases.

Drisko and Bastian believe that abnormal prions exist with the diseases. But they think Spiroplasma is triggering the abnormal prion changes as a way to hide in cells from the body’s immune system.

The bacterium’s toughness might allow it to survive in cattle or wildlife feeds that include high-protein supplements made from rendered animals, Drisko said. That is how many experts think the diseases have spread.

Prion research can provide some tests and treatments, Drisko said, because some infective agent is present in prions. But, if the agent is present but has not yet produced prions or other signs, the diseases can avoid detection. Spongiform diseases can take years to develop after exposure, experts say.

Bastian has a $125,000 grant from the National Institutes of Health for his DNA work, and he’s planning to expand. The Department of Agriculture is giving him scrapie samples for research.

Experts say what Bastian needs to prove is that Spiroplasma is present as a cause and not as a result of the infection.

“It’s up to them to produce the data that are strong enough so others follow their lead,” said Janice Miller, a chronic wasting research director at the agency’s veterinary laboratory in Ames, Iowa.

Drisko said Bastian was close. “I can’t tell you how many things in science that were originally met with scorn and derision later turned out to be right,” she said.

 

Adapted from an article by Bill Graham in the Kansas City Star, Sept. 9, 2002.

Rich Forrest of the CWD Foundation has been working with Dr. Bastian by providing him with positive CWD samples and helping raise additional research funds. If prion type diseases are caused by this bacterium, this would also explain why Italian scientists, as reported in our August 2002 issue, found antibiotics significantly slowed progress of the disease.