Chronic Wasting Disease

The Chronic Wasting Disease (CWD; German Chronic wasting disease literally ) is an infectious disease of the central nervous system in deer, the spongiform encephalopathies is expected to. It is similar to bovine spongiform encephalopathy ( BSE) in cattle and Creutzfeldt -Jakob disease in humans.

History

The Chronic Wasting Disease was first described in the late 1960s in a herd of mule deer in Colorado as a syndrome. In the late 1970s, it was found that this is similar to the long-known scrapie of sheep to a spongiform encephalopathy.

Dissemination

Chronic Wasting Disease is in the western part of North America before, of course. It affects wild mule deer, white-tailed deer and elk in Wyoming, Colorado, Nebraska, South Dakota and Wisconsin. In captive deer herds, the disease was also found in other western United States and in western Canada. The prevalence can be up to 100 % in affected herds in captivity; in the wild prevalences of be found under one to over 30 percent.

The disease has been diagnosed only once outside of North America, in South Korea in a herd of elk imported from Canada.

Pathogen

As with the other transmissible spongiform encephalopathies is the causative agent believed to be an abnormally folded prion, which however has not yet been isolated. The transmission from animal to animal; a transmission from mother to offspring may occur, but has no great significance for the transmission. Experimental CWD can be transmitted directly into the brain on cattle, sheep, goats, ferrets, mink, mice, golden hamsters and squirrel monkeys by injection of infectious material.

The natural infection is suspected by the oral route; the modified protein is then probably taken up by the Peyer's patches of the gut-associated immune system and travels well through the vagus nerve to the brain where it accumulates and gradually leads to the formation of spongiform changes in the brain.

It is unknown in what way, an infected animal excretes the infectious agent again, but excretion via the faeces seems likely. Since prions are very resistant in the environment, it is possible that the accumulation in the environment - especially with enclosure attitude - plays an important role in the transmission. In the wild, probably also play the carcasses of dead deer a role in the transmission.

Symptoms

Contracted CWD deer are usually older than 16 months. The first symptoms are discrete, first barely perceptible changes in behavior, followed by weight loss. They fall into captivity often on the nursing staff. With progression of the disease leads to apathy, somnolence, loss of natural shyness, compulsive walking, increased thirst and increased irritability when touched. This often problems come in the coordination of movements, which are manifested in ataxia and head tremor. Secondarily it can also lead to aspiration pneumonia because of the damage to the nervous system, because the disease interferes with the swallowing process. Throughout the course of the disease, it also leads to a progressive loss of weight, from which the name for CWD.

Diagnosis

Diagnosis is made by microscopic examination of tissue samples from the brain, in which the characteristic changes of the sponge-like nerve tissue can be detected. There are also routine testing on the basis of ELISA may be based on neural and lymphoid tissue. In mule and white -tailed deer, the agent accumulates in the Retropharyngeallymphknoten even before it reaches the brain, so this fabric for a test is most important. In the brain, the rear end of the fourth Hirnventrikels is best suited for the detection of pathogens.

The differential diagnosis should rabies, brain abscess, meningitis, encephalitis, malnutrition, peritonitis, and dental problems are considered.

CWD is a notifiable disease in both North America and Europe.

Treatment and prevention

There is no effective treatment for chronic wasting disease. Affected animals have to be culled. The prevention happens in captivity have appropriate herd management, which is coordinated by the Canadian and American Veterinary which also awarded appropriate certificates for deer herds. To achieve the highest certification a herd requires at least five years.

The agent is very stable in the environment. It can disable it for 30-60 minutes so far only by disinfection with 50 % Javelle water. Infected carcasses should be incinerated in a facility equipped for that purpose.

The control of CWD is designed to be extremely difficult in the wild. Such programs use a strong Monitoring and Surveillance System, hunting bans, population reductions, as well as trapping of affected animals.

Risk to humans

The risk to humans appears to be minimal. CWD is at least 30 years spread in deer populations that are hunted regularly. Nevertheless, so far not a single case of the disease has been diagnosed in humans. When precautions are recommended not obviously sick animals to shoot in the Enzootiegebieten for consumption to wear latex gloves when gutting, to avoid contact with nervous and lymphatic tissues, disinfect all knives used for breaking down the prey and other devices in 50 % Javelle water and the to get tested animal for CWD.