August 9, 2002 Rocky Mountain News (Denver, CO) by Todd Hartman
|Neurologists in Denver want to examine hunters from northeastern Colorado
showing early signs of dementia to assess whether they could have contracted
human cases of chronic wasting disease.
The research, to be overseen by University of Colorado Health Sciences Center doctors, comes as the state health department plans to review decades' worth of death rec-
ords to see if deaths related to brain diseases are uncommonly high in Colorado's CWD endemic area.
Patrick Bosque, a neurologist at Denver Health Medical Center, said it's time to look more directly for patterns linking CWD with human deaths, because experimental models designed to answer the question of human susceptibility aren't working well enough.
"The only way we're going to know is if we see an outbreak (of dementia-like brain disease in humans) that can be tied back to deer and elk consumption," said Bosque, whose mice experiments relating to human risk of CWD are inconclusive. Looking for cases in the northeastern Colorado endemic area is the obvious way to go, he said.
"A lot of science comes down to common sense," Bosque said. "If (CWD) is transmissible, that's where we're going to see it first."
Bosque said the study involving living hunters and perhaps others who consumed venison frequently would likely involve mailing letters to neurologists and primary care clinics, who would refer dementia patients from northeastern Colorado for a formal evaluation at CU Health Sciences Center.
Among things neurologists would look for: A pattern of deterioration similar to other prion diseases. Prions are rogue proteins believed to be at the root of CWD, mad cow disease, and a related human disease called Creutzfeldt-Jakob, or CJD.
"We'd want to see something that's getting worse," Bosque said. "Prion diseases progress fairly rapidly; they're not something that progresses over a 10-year period, something on the order of a month-
to-month, steady worsening."
The long incubation period of prion diseases could make the assessment more difficult, Bosque said. Someone could have stopped eating venison decades ago and, in theory at least, show symptoms far later.
Citing a related degenerative disease, called kuru, that struck tissue-
eating cannibals in New Guinea, Bosque said scientists discovered incubation periods of 30 to 40 years.
The Colorado Department of Public Health and Environment, meanwhile, is contracting with statisticians at the CU Health Sciences Center to crunch death records for diagnoses of dementia-like diseases such as Alzheimer's, Creutzfeldt-Jakob and senility to see if unusually high numbers of those causes of death appear in northeastern Colorado compared with rates elsewhere in the state.
State epidemiologist John Pape actually sought the $22,000 study a year ago, but was initially turned down for funding by the Centers for Disease Control. Now, with money in hand, he hopes to see the work completed by early next year.
"It wouldn't tell us, if we saw higher rates (of brain diseases), that it was CWD," Pape said. "But it would be a roadmap, telling us maybe we ought to look at this more, or look at some of these cases to see what occurred there."
Pape said health officials in Great Britain conducted a similar analysis - seeking 30 to 40 diagnoses for deaths linked to neurological diseases - prior to the outbreak of the human form of mad cow disease, when they were still only wondering if the disease could make the jump from animals to people. Since then, 135 cases have been documented in humans. Even so, the early statistical analysis failed to pick out any glaring patterns.
If the Colorado study did show unusually high death rates from brain maladies in the endemic area, health officials would have to take additional steps, including looking at old medical records and talking to surviving family members.
"It's kind of a crude measure," Pape said. "What I think it will show is nothing, that people who hunt in those counties probably don't die of a lot of strange neurological diseases any more than people in the southern and western part of the state, where CWD hasn't occurred."