Chronic Wasting Disease

Author: Mariano Carossino, DVM, Ph.D., DACVP, DACVM, Assistant Professor of Veterinary Pathology

Overview

Chronic Wasting Disease (CWD) is a contagious and fatal neurological disease that affects white-tailed deer and other members of the deer family, including mule deer, elk, reindeer, muntjac and moose. It belongs to a group of disorders known as transmissible spongiform encephalopathies (TSEs), which are caused by abnormal, misfolded natural proteins known as prions. These prion proteins gradually accumulate in the nervous system, leading to the slow development of clinical signs.

Clinical signs

Infected deer may appear healthy for months or years after infection. As the disease progresses, they begin to show clinical signs, including:

• Noticeable weight loss (“wasting”)
• Drooling or excessive salivation
• Drooping ears and a lowered head
• Frequent urination
• Difficulty swallowing, which can lead to aspiration pneumonia
• Unusual behavior such as lack of fear of humans, confusion, or listlessness
• Poor coordination and staggering movements

This disease is fatal, and infected animals eventually become weak and die.

Exposure, Transmission and Incubation

CWD spreads through direct contact between animals and indirectly through contaminated items in the environment such as soil, dust, or forages. Infected deer shed infectious prions into the environment through their saliva, urine, and feces, and also from infected body tissues. Infectious prions can remain in soil, plants, and water for years, which makes controlling the disease very challenging. Because of this long environmental persistence, once CWD becomes established in an area, it is extremely difficult to eliminate.

CWD enters the body either orally and/or intranasally and infectious prions amplify initially in lymph nodes and other lymphoid tissues before they reach the brain. Infected animals can appear healthy for months or years. During this 'silent' incubation period, infected animals can shed prions in their excreta and transmit the disease to other animals. How fast CWD progresses depends on the species and the animal's genetics.

Geographic Distribution and Impact

CWD has been detected in both wild and captive deer populations across many parts of the United States and Canada. CWD has been detected in 36 U.S. states. In Louisiana, CWD was detected for the first time in wild deer in 2022 in Tensas Parish, and additional positive detections were identified in Catahoula Parish in 2025. The Louisiana Department of Wildlife and Fisheries (LDWF), as many other wildlife agencies across the country, actively monitor deer herds through surveillance programs.

CWD poses a serious threat to deer populations, hunting traditions, and the health of natural ecosystems. Maintaining healthy deer herds is important for biodiversity, recreation, and local economies.

Impact to Human Health

There is currently no evidence that CWD can infect humans. However, as a precaution, the Centers for Disease Control and Prevention (CDC) recommends that people do not consume meat from animals that test positive for CWD. Hunters should have their deer tested in areas where the disease is known to occur and wear gloves when field dressing or processing animals.

Prevention and Reporting

There is no cure or vaccine against CWD. For these reasons, early detection and control are key to preventing further spread. The public can help by:

• Reporting sick or unusually behaving deer to local wildlife authorities
• Following state guidelines for carcass transport and disposal
• Participating in deer testing programs when hunting
• Avoiding practices that concentrate deer unnaturally, such as feeding or baiting

By staying informed and working together, hunters, landowners, and wildlife managers can help protect white-tailed deer and ensure healthy wildlife populations for future generations.

Testing at the Louisiana Animal Disease Diagnostic Laboratory (LADDL)

As a member of the National Animal Health Laboratory Network (NAHLN), LADDL is an approved laboratory for CWD testing using the immunohistochemistry test approved by the National Veterinary Services Laboratories (NVSL), United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS).

Testing can be performed from nervous tissue (obex) and retropharyngeal lymph nodes or tonsil from hunter-harvested deer heads.

To submit a head for CWD testing:

1. Fill our submission form and include the GPS location of where the deer was harvested.
2. Please indicate in the form whether the deer had any evidence of disease (see clinical signs section above for reference).
3. Remove the deer head 5 inches below the ear (deer heads may be caped, with antlers and skull cap removed), place heads on ice in an ice chest or refrigerated and submit to the laboratory. DO NOT FREEZE.