‘Disease from outer space’ States confront the spread of CWD in deer

In March, 1996, the UK government confirmed what had been known for years: bovine spongiform encephalopathy (or mad cow disease) was killing humans in the UK.

The various forms of transmissible encephalopathies have different names according to the species – scrapie in sheep, feline spongiform encephalopathy in cats, Creutzfeldt-Jacob disease in humans, chronic wasting disease in deer and elk.

But they’re all the same affliction, caused by infectious proteins, or prions.

I haven’t been following the CWD outbreak in deer, but it seems to be where BSE was about 1993: There’s this mysterious new disease no one ever thoughts would cross over to humans, but now, maybe?

Jim Robbins of the New York Times writes that, as darkness closed in, one hunter after another stopped at this newly opened game check station, deer carcasses loaded in the beds of their pickups.

They had been given licenses for a special hunt, and others would follow. Jessica Goosmann, a wildlife technician with Montana’s Fish, Wildlife & Parks Department, stepped outside to greet them, reaching for the neck of each freshly killed deer to cut an incision and remove a lymph node for testing.

On the edge of this south-central Montana village, where deer hunting is a way of life, the game check station has become the front line of the state’s efforts to stop the spread of a deadly infection known as chronic wasting disease.

It has ravaged deer herds throughout the United States and Canada and forced the killing of thousands of infected animals in 24 states and three Canadian provinces. It has also been found in Norway and South Korea. With the disease widespread in Wyoming, the Dakotas and the province of Alberta, Montana officials had been bracing for its emergence.

So in November, when biologists discovered it in six deer in this part of Montana and in another near the Canadian border, officials began setting up special hunts and stations for testing.

“It wasn’t a surprise that we found it,” said John Vore, game management bureau chief for the Montana Department of Fish, Wildlife & Parks. “It was a disappointment, but not a surprise.”

On Friday, the department announced that two more deer from this region, taken early in the special hunt, tested positive for the disease. Other test results are pending.

Chronic wasting disease is a contagious neurological disease that infects elk, deer, moose and caribou, and reduces their brains to a spongy consistency. Animals become emaciated, behave strangely and eventually die. It’s not known to be transferred to humans. Neither is it known to be spread from wild to domestic animals. There is no treatment, although a vaccine has been successful in tests in wild deer.

It is among a class of diseases known as transmissible spongiform encephalopathy, or TSE. Most experts believe the infectious agent is something called a prion, a misfolded cellular protein found in the nervous system and lymph tissue. The disease was first noted in captive deer in Colorado in the 1960s. The most closely related animal disease is scrapie in sheep.

“It’s a very unusual disease,” said Matthew Dunfee, an expert at the Wildlife Management Institute in Fort Collins, Co. and project director for the Chronic Wasting Disease Alliance. “Some experts say it’s a disease from outer space.”

 

Wow: Grass plants can transport infectious prions

Grass plants can bind, uptake and transport infectious prions, according to researchers at The University of Texas Health Science Center at Houston (UTHealth). The research was published online in the latest issue of Cell Reports.

prion.plants.may.15Prions are the protein-based infectious agents responsible for a group of diseases called transmissible spongiform encephalopathy, which includes bovine spongiform encephalopathy (mad cow disease) in cattle, scrapie in sheep, variant Creutzfeldt-Jakob disease in humans and chronic wasting disease (CWD) in deer, elk and moose. All are fatal brain diseases with incubation periods that last years.

CWD, first diagnosed in mule deer in Colorado in the late 1960s, has spread across the country into 22 states, according to the Centers for Disease Control and Prevention (CDC), including the counties of El Paso and Hudspeth in Texas. In northeastern Colorado and southeastern Wyoming, the disease is endemic. Soto’s team sought to find out why.

“There is no proof of transmission from wild animals and plants to humans,” said lead author Claudio Soto, Ph.D., professor of neurology at UTHealth Medical School and director of the UTHealth George and Cynthia W. Mitchell Center for Alzheimer’s Disease and Other Brain Related Illnesses. “But it’s a possibility that needs to be explored and people need to be aware of it. Prions have a long incubation period.”

Soto’s team analyzed the retention of infectious prion protein and infectivity in wheat grass roots and leaves incubated with prion-contaminated brain material and discovered that even highly diluted amounts can bind to the roots and leaves. When the wheat grass was consumed by hamsters, the animals were infected with the disease. The team also learned that infectious prion proteins could be detected in plants exposed to urine and feces from prion-infected hamsters and deer.

Researchers also found that plants can uptake prions from contaminated soil and transport them to different parts of the plant, which can act as a carrier of infectivity. This suggests that plants may play an important role in environmental prion contamination and the horizontal transmission of the disease.

To minimize the risk of exposure to CWD, the CDC recommends that people avoid eating meat from deer and elk that look sick or test positive for CWD. Hunters who field-dress deer in an affected area should wear gloves and minimize handling of the brain and spinal cord tissues.

“This research was done in experimental conditions in the lab,” Soto said of the next step. “We’re moving the research into environmental contamination now.”

First author of the paper, “Grass Plants Bind, Retain, Uptake and Transport Infectious Prions,” is post-doctoral researcher Sandra Pritzkow, Ph.D. Co-authors from UTHealth are Rodrigo Morales, Ph.D.; Fabio Moda, Ph.D.; and Uffaf Khan. Co-authors from the Prion Research Center at the College of Veterinary Medicine and Biomedical Sciences, Colorado State University, are Glenn C. Telling, Ph.D.; and Edward Hoover, D.V.M., Ph.D.

First successful vaccination against ‘mad cow’-like wasting disease in deer

Researchers at NYU Langone Medical Center and elsewhere say that a vaccination they have developed to fight a brain-based, wasting syndrome among deer and other animals may hold promise on two additional fronts: Protecting U.S. livestock from contracting the disease, and preventing similar brain infections in humans.

deerThe study, to be published in Vaccine online Dec. 21, documents a scientific milestone: The first successful vaccination of deer against chronic wasting disease (CWD), a fatal brain disorder caused by unusual infectious proteins known as prions. Prions propagate by converting otherwise healthy proteins into a disease state.

Equally important, the researchers say, this study may hold promise against human diseases suspected to be caused by prion infections, such as Creutzfeldt-Jakob disease, kuru, familial insomnia, and variably protease-sensitive prionopathy. Some studies also have associated prion-like infections with Alzheimer’s disease.

“Now that we have found that preventing prion infection is possible in animals, it’s likely feasible in humans as well,” says senior study investigator and neurologist Thomas Wisniewski, MD, a professor at NYU Langone.

CWD afflicts as much as 100 percent of North America’s captive deer population, as well as large numbers of other cervids that populate the plains and forests of the Northern Hemisphere, including wild deer, elk, caribou and moose. There is growing concern among scientists that CWD could possibly spread to livestock in the same regions, especially cattle, a major life stream for the U.S. economy, in much the same manner that bovine spongiform encephalopathy, or Mad Cow Disease, another prion-based infection, spread through the United Kingdom almost two decades ago.

According to Dr. Wisniewski and his research team, if further vaccine experiments prove successful, a relatively small number of animals (as few as 10 percent) could be inoculated to induce herd immunity, in which disease transmission is essentially stopped in a much larger group.

For the study, five deer were given the vaccine; another six were given a placebo. All of the deer were exposed to prion-infected brain tissue; they also were housed together, engaging in group activities similar to those in the wild. Scientists say this kept them in constant exposure to the infectious prions. The animals receiving the vaccine were given eight boosters over 11 months until key immune antibodies were detectable in blood, saliva, and feces. The deer also were monitored daily for signs of illness, and investigators performed biopsies of the animals’ tonsils and gut tissue every three months to search for signs of CWD infection.

Within two years, all of the deer given the placebo developed CWD. Four deer given the real vaccine took significantly longer to develop infection—and the fifth one continues to remain infection free.

Wisniewski and his team made the vaccine using Salmonella bacteria, which easily enters the gut, to mirror the most common mode of natural infection—ingestion of prion-contaminated food or feces. To prepare the vaccine, the team inserted a prion-like protein into the genome of an attenuated, or no longer dangerous, Salmonella bacterium. This engineered the Salmonella to induce an immune response in the gut, producing anti-prion antibodies.

“Although our anti-prion vaccine experiments have so far been successful on mice and deer, we predict that the method and concept could become a widespread technique for not only preventing, but potentially treating many prion diseases,” says lead study investigator Fernando Goni, PhD, an associate professor at NYU Langone.