Photo © Sam Stukel

CWD Definitions

Several terms frequently pop up when discussing CWD.  In order to help better understand CWD and the language surrounding CWD this list of common terms will help you speak the language and better understand the information presented.


The active and efficient cause of a disease; usually refers to a germ such as a virus, bacteria, or prion. 

Bovine spongiform encephalopathy (BSE)

A transmissible spongiform encephalopathy (see below) affecting cattle, caused by a prion.  Transmission between cattle normally takes place when cattle are fed meat and bone meal originating from cattle that were affected by BSE.

Captive cervid herd

A herd of deer or elk that is confined and managed as a herd of domestic animals would be.

Central nervous system

The brain and spinal cord. 

Cervidae, Cervids

A mammal of the family Cervidae, which includes white-tailed deer, mule deer and elk.

Clinical signs

Something abnormal, relevant to disease in an animal, detected and possibly measured by an observer.  Animals are considered to have clinical signs instead of “symptoms.”


The designation for an animal that has been determined to have been infected with the CWD prion.


                Removing cuts of meat from the attached bone. 

Disease distribution

The patterns in which cases of disease are found, e.g., geographically, over certain time periods, gender or age of diseased animals, etc.

Endemic area

A geographic area in which animals affected with a certain disease would normally be expected to be found.


Being subjected to an infectious agent.

Hunter-harvest survey

A surveillance method in which hunters voluntarily submit their harvested deer or elk for CWD-testing. 

Lymphoid tissue

Portions of the body that house lymphocytes (certain cells involved in the immune response).  Lymphoid tissue can be diffuse in nature, as in certain parts of the intestine; or it can be focused in small organs distributed throughout the body called lymph nodes.


Pertaining to the function of the brain, spinal cord, and nerves.


A germ capable of creating damage to a body function or organ, resulting in illness or disease.

Population dynamics

A branch of knowledge concerned with the sizes of populations and the factors involved in their maintenance, decline, or expansion.


The documentation of CWD in a given population or hunting unit.

Prevalence/Prevalence rate

The percentage of cervids in a population or hunting unit that are infected with CWD.


A form of a protein molecule that is closely associated with cells in the nervous system and in lymphoid tissue.  When abnormal prions come in contact with normal cellular proteins, they can convert them to the abnormal form.  Prions are the smallest and most basic of all infectious agents.  They are very resistant to enzymes, chemicals, heat, and normal disinfecting procedures. 

Retropharyngeal lymph nodes

Lymph nodes (see above) located in the back of the upper throat of the animal.  In harvested deer, they are frequently used as a sample for CWD testing.


A transmissible spongiform encephalopathy that exclusively affects sheep and goats. 


The regular monitoring of an animal population for the presence of disease.

Transmissible spongiform encephalopathies (TSE’s)

Diseases that are caused by abnormal forms of prions that convert normal cellular proteins to more abnormal prions.  The net effect of this conversion is the formation of plaques of protein in nervous or lymphoid tissue (usually the brain), which eventually create spaces or “holes” in that tissue.  “Spongiform” refers to the sponge-like appearance of this tissue under a microscope, while “encephalopathy” refers to the resulting abnormal function of the brain.


Describes a disease that can be transmitted from animals to people under natural conditions.