MONDAY, May 23 (HealthDay News) -- U.S. researchers have new information about how humans are exposed to "prion" diseases, which are rare, progressive conditions that affect brain function, such as variant Creutzfeldt-Jakob disease, chronic wasting disease and bovine spongiform encephalopathy, commonly known as "mad cow disease."

The study, published in the June issue of the Journal of the American Dietetic Association, found that eating wild deer meat (venison) is one of the most common ways people are exposed to these serious, debilitating diseases.

"While prion diseases are rare, they are generally fatal for anyone who becomes infected. More than anything else, the results of this study support the need for continued surveillance of prion diseases," the study's lead investigator Joseph Y. Abrams, of the National Center for Emerging and Zoonotic Infectious Diseases at the U.S. Centers for Disease Control and Prevention, said in a journal news release.

"But it's also important that people know the facts about these diseases, especially since this study shows that a good number of people have participated in activities that may expose them to infection-causing agents," Abrams added.

In examining the results of a 2006-2007 population survey conducted by the Foodborne Diseases Active Surveillance Network (FoodNet), CDC researchers were able to track how participants may have been exposed to prion diseases, including:

• Travel to countries where bovine spongiform encephalopathy ("mad cow") is known to be widespread, including the United Kingdom, Republic of Ireland, France, Portugal, Switzerland, Italy, the Netherlands, Germany and Spain.
• Hunting for deer or elk -- especially in regions where chronic wasting disease is considered common (northeastern Colorado, southeastern Wyoming and southwestern Nebraska).
• The consumption of venison -- particularly deer meat obtained in the wild.

The investigators found that 29.5 percent of those polled traveled to at least one of the nine countries where bovine spongiform encephalopathy was widespread, with the United Kingdom being the most common destination (19.4 percent of survey participants). Travelers to the United Kingdom were also more likely to stay longer. In fact, nearly one-quarter remained in the country for at least a month.

Moreover, 18.5 percent of those polled hunted for deer and 1.2 percent hunted for elk in regions known for chronic wasting disease. Venison was eaten by 67.4 percent of those surveyed. Of those who ate deer meat, 88.6 percent got it from the wild.

Based on these findings, the CDC researchers concluded that hunters in these areas should protect themselves from exposure to chronic wasting disease by taking the following steps: do not eat meat from sickly deer or elk; don't eat brain or spinal cord tissues; minimize the handling of brain and spinal cord tissues; and wear gloves when field-dressing carcasses.

"The 2006-2007 FoodNet population survey provides useful information should foodborne prion infection become an increasing public health concern in the future. The data presented describe the prevalence of important behaviors and their associations with demographic characteristics. Surveillance of bovine spongiform encephalopathy, chronic wasting disease and human prion diseases are critical aspects of addressing the burden of these diseases in animal populations and how that may relate to human health," Abrams concluded.

More information

The U.S. Centers for Disease Control and Prevention offers detailed information on prion diseases.