A deadly disease with no known cure is killing deer in dozens of states and multiple provinces.

Chronic wasting disease (CWD) affects the central nervous system of deer and related animals, such as moose and caribou. It is believed to be responsible for population declines among certain deer and elk.

Animals suffering from CWD may develop symptoms including lack of co-ordination, unusual behaviour, excessive production of bodily fluids and severe weight loss. Their bodies continue to deteriorate, and the animals die within weeks or months.

The disease can spread between animals through saliva, feces or urine. In one case, hamsters became infected after consuming plants which grew in CWD-contaminated soil.

No evidence has been found to suggest that affected animals can pass the disease on to humans, although authorities do recommend that humans not consume affected animals as a precaution.

Because of its ability to put deer populations into decline, CWD has been called “one of the biggest issues deer hunters and managers are facing today” by the Quality Deer Management Association.

The magnitude of the threat it represents has led to conservation authorities spending significant time and resources to curtail CWD, despite its slow spread through North America.

The disease was first discovered in 1967 in Colorado. Its presence has grown significantly in the past 15 years. Wild animals have tested positive for the disease in 24 states, as have captive animals. Infection rates in some wild herds have been reported to be as high as one in four.

In Canada, six cases of CWD were found in 2018. Authorities found that the disease had infected three elk herds and one group of deer in Saskatchewan, as well as an elk herd in Alberta.

More concerning was the discovery last September of CWD on a red deer farm in western Quebec, suggesting for the first time that the disease had become a threat to animals in Eastern Canada.

Canadian authorities discover about five infected herds per year, with the vast majority of diagnoses being made in Saskatchewan, where the disease was first spotted in Canadian wildlife in 1996.

Deer populations are tested for the disease in provinces where CWD has yet to be discovered, and some provinces have rules banning the importation of deer carcasses from jurisdictions where CWD is known to occur.

The disease has also been found in Norway, Finland and South Korea.

With files from The Associated Press