Infectious Nature of CWD — How Does It Spread?

Transmission through Direct Contact

Chronic wasting disease (CWD) is primarily transmitted through direct contact with infected cervids. This can occur when an animal comes into close proximity with an infected individual, allowing the exchange of contaminated saliva, urine, or feces. Studies have shown that a single infected animal can contaminate a large area, with one study finding that an infected elk can contaminate up to 1.6 square kilometers of habitat. The risk of transmission increases when multiple animals are present in a small area, such as in deer farms or hunting camps.

Transmission through Contaminated Food and Water

CWD can also spread through contaminated food and water sources. Infected animals can shed prions in their saliva, urine, and feces, which can then be ingested by other animals through contaminated food sources. This can occur when animals feed on plants that have been contaminated with prions from infected animals. Similarly, contaminated water sources, such as streams and rivers, can also pose a risk of transmission. In one study, it was found that prions can survive in water for up to 3 years, highlighting the potential risk of waterborne transmission.

Insect Vectors and Environmental Factors

While the exact role of insect vectors in CWD transmission is not yet fully understood, research suggests that they may play a role in the spread of the disease. Insects such as ticks and flies can potentially come into contact with prions and transport them to other animals. Environmental factors, such as temperature and humidity, can also influence the survival and transmission of CWD prions. For example, studies have shown that prions can survive for longer periods in cooler temperatures and high humidity, increasing the risk of transmission in these environments.