As CWD spreads in cervids, states also monitor humans

As a fatal, infectious neurologic disease has spread in deer and elk, researchers want to make sure it can't affect humans.

Dr. Jennifer House, Colorado's state public health veterinarian, said chronic wasting disease has no known link to disease in humans. But public health authorities are performing surveillance in three states—Colorado, Wisconsin, and Wyoming—to watch for ailments and deaths that could be connected with the prion disease.

Dr. House, in a presentation at AVMA Convention 2018, July 13-17 in Denver, said the evidence so far suggests hunters and people who eat meat from deer and elk are at no increased risk of developing the disease. But she noted that, in one of two studies, some macaques fed prion-contaminated meat developed the disease.

The National Prion Disease Pathology Surveillance Center at Case Western Reserve University, the Centers for Disease Control and Prevention, and state health departments have collaborated to watch for potential human infections in areas where CWD is endemic, university information states.

In her presentation, Dr. House described the history of prion disease discovery, the prion diseases affecting humans, and their causes. She said about one person in a million will develop Creutzfeldt-Jakob disease, a sporadic, fatal neurodegenerative disorder caused by a genetic mutation that causes a chain reaction of misfolded prion proteins.

Sporadic mutations account for 90 percent of CJD cases, she said, and inherited mutations account for about 10 percent.

A few hundred people have developed variant CJD, typically from eating meat contaminated with the prion that causes bovine spongiform encephalopathy, she said. But she said those cases have drawn public attention to prion diseases.

As for CWD, the disease kills deer, elk, reindeer, and moose. Misfolded prion proteins can spread among cervids through saliva and excrement, and they may remain viable in environments for decades.

Clinical signs of CWD include confusion, weight loss, increased thirst and urination, and drooling.

The disease was discovered in the late 1960s in captive deer in Colorado, and by 1981 it had spread to wild deer, according to the CDC and the U.S. Geological Survey. The disease spread among herds in Colorado and Wyoming by the 1990s and since has been found in more than 20 other states.

Related JAVMA content:

Chronic wasting disease continues to spread (Aug. 15, 2017)