Chronic wasting disease or CWD is a contagious disease of the brain and central nervous system that is always fatal to deer, elk, moose, caribou and other members of the deer family. It is one of the most serious wildlife diseases facing state wildlife agencies such as the FWC because it could substantially reduce infected deer populations. CWD has been detected in Florida and the FWC is working with the Florida Department of Agriculture and Consumer Services, hunters, captive cervid owners, landowners, and the public to reduce the risk of CWD spreading in Florida.
Why CWD is a concern
CWD is one of the most serious wildlife diseases facing state wildlife agencies such as the FWC. This disease could substantially reduce infected deer populations by lowering adult survival rates and destabilizing long-term population dynamics.
Can CWD impact people?
Currently, there is no scientific evidence that CWD can be transmitted to humans under natural conditions. However, the Centers for Disease Control and Prevention do not recommend consuming meat from animals that test positive for CWD or from any sick animal. The FWC provides information about precautions people should take when pursuing or handling deer that may have been exposed to CWD.
What causes CWD?
CWD is believed to be caused by a naturally occurring protein called a prion that becomes misfolded and resists being broken down by the body the way normal proteins are. When these misfolded proteins are introduced into a healthy member of the deer family, they multiply and begin accumulating in and damaging the animal’s brain and central nervous system.
Is CWD treatable?
There is no known cure for prion diseases and vaccines have been ineffective. Since the prion is so persistent and stable, treatment or decontaminating the environment is extremely difficult and largely ineffective.
Signs of the disease
Signs of the disease usually appear 1 1/2 to 3 years after initial exposure so deer can be infected and shedding prions (infectious to others) but look normal. Typically, CWD is characterized by extreme weight loss and abnormal behaviors such as listlessness, lowering of the head, inattentiveness toward people, walking in circles, staggering, and standing with a wide stance. Death usually occurs within 4 months of the onset of clinical signs, although some animals may survive for up to a year. CWD is always fatal once a member of the deer family is infected.
How CWD is transmitted
The abnormal proteins or prions that cause CWD can be transmitted through direct animal-to-animal contact. Members of the deer family can also become infected through contact with the saliva, urine, feces, blood and carcass parts of an infected animal. It can even spread through soil. Leaving CWD infected carcasses or carcass parts on the land can contaminate the soil and the CWD prions are capable of infecting other deer for years.
Locally, and even regionally, the disease appears to spread naturally through the movement and dispersal of deer and other cervids with CWD. Transporting hunter-killed carcasses with CWD also may spread the disease. Moving infected captive deer, elk, moose and caribou is believed to be one of the primary ways CWD is spread over long distances in North America. Importing live deer, elk, moose, caribou, and other members of the deer family into Florida was banned in 2013.
See this infographic about how CWD is transmitted.
Where CWD has been detected
CWD has been found in captive and/or free-ranging members of the deer family in 31 states in the U.S.
CWD also has been detected in the Canadian provinces of Alberta, Manitoba, Quebec, and Saskatchewan as well as Finland, Norway, Sweden, and South Korea.
Can CWD be controlled or eradicated?
Once CWD has been established, it is difficult to control the spread of CWD and virtually impossible to eradicate. Because prions shed by infected deer persist in the environment, the best chance for managing CWD is acting quickly after it’s been detected to prevent more animals from becoming infected. CWD can be transmitted directly - from animal to animal - or indirectly from the environment. Higher concentrations of deer increase the likelihood of transmission. Since CWD has been detected FWC is using multiple management strategies to control the spread of the disease, including purposefully lowering the deer population in the infected area.
How do epizootic hemorrhagic disease (EHD) and bluetongue virus (BTV) compare to CWD?
The impact of EHD and BTV on deer populations can be periodic, localized outbreaks that are highly visible. However, large mortality events caused by these viruses are not common in Florida. When they do occur, deer numbers eventually rebound. While the impacts of CWD are less immediately apparent than EHD outbreaks, CWD is a greater and more long-term threat to Florida’s deer population. To learn more about this topic, read “Yes, EHD is Bad. But CWD is Worse.”