Chronic wasting disease

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Spread of Chronic Wasting Disease 2014

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

history

Chronic wasting disease was first described as a syndrome in a herd of mule deer in Colorado in the late 1960s . In the late 1970s, it was discovered to be a spongiform encephalopathy similar to the long-known scrapie of sheep . Colloquially , the disease is also known by the lurid name of zombie disease, due to the behavior of sick animals, which is reminiscent of zombies .

distribution

Chronic wasting disease occurs naturally in western North America . It affects wild mule deer, white-tailed deer and elk in Wyoming , Colorado , Nebraska , South Dakota and Wisconsin . In captive herds of deer, the disease has also been found in other western states of the United States and in western Canada . The prevalence in infested herds in captivity can be up to 100%; in the wild, prevalences of less than one to over 30 percent are found.

The first known European case was a female reindeer from the Nordfjella population in southern Norway , in which the pathogen was detected in 2016. CWD has also performed in Finland. In South Korea , the disease occurred in a herd of elk deer imported from Canada.

Pathogen

As with the other transmissible spongiform encephalopathies, the pathogen is probably an abnormally folded prion , which, however, has not yet been isolated. The transmission takes place from animal to animal; transmission from the mother to the offspring can occur, but is of no great importance for the transmission. Experimentally, CWD can also be transmitted to cattle, sheep, goats , ferrets , minks , mice , golden hamsters and squirrel monkeys by injecting infectious material directly into the brain .

The natural infection presumably occurs via the oral route; The modified protein is then presumably absorbed by the Peyer's plaques of the intestinal-associated immune system and probably migrates via the vagus nerve into the brain, where it accumulates and gradually leads to the formation of the spongiform brain changes.

It is not known how an infected animal excretes the infectious agent, but excretion in the faeces seems likely. Since prions are very resistant in the environment, it is possible that their accumulation in the environment - especially when kept in a cage - plays an important role in transmission. In the wild, dead deer carcasses are also likely to play a role in transmission.

Symptoms

Deer with CWD are usually older than 16 months. The first symptoms are discrete, at first barely noticeable changes in behavior, followed by weight loss. They are often noticed by nursing staff in captivity. As the disease progresses, there is apathy , somnolence , loss of natural shyness, compulsive walking, increased thirst and increased excitability when touched. In addition, there are often problems with the coordination of movements, which are expressed in ataxia and head tremors . Secondarily, the damage to the nervous system can lead to aspiration pneumonia , as the disease disrupts the swallowing process. During the entire course of the disease, there is also a progressive weight loss, which gave CWD its name.

diagnosis

Histopathological changes in CWD. A: Spongiform change in the root of the vagus nerve in the elongated medulla. B: Immunological staining of PrP surrounded by vacuoles. C: Abnormal PrP deposits. D: Abnormal PrP in the tonsils of a mule deer

The diagnosis is made by microscopic examination of tissue samples from the brain, in which the characteristic spongy changes in the nerve tissue can be detected. There are also routine tests based on an ELISA , which can be based on nerve and lymphoid tissue. In mule and white-tailed deer, the agent accumulates in the retropharyngeal lymph nodes before it reaches the brain, making this tissue the most important tissue for a test. In the brain, the rear end of the fourth cerebral ventricle is best suited for the detection of pathogens. Recent diagnostic developments also use saliva samples for ante mortem tests .

The differential diagnosis should consider rabies , brain abscesses , meningitis , encephalitis , malnutrition, peritonitis, and dental problems.

CWD is a reportable animal disease in both North America and Europe .

Treatment and prevention

There is no effective treatment for chronic wasting disease. Affected animals must be culled . Prevention occurs in captivity through appropriate herd management, which is coordinated by the Canadian and US veterinary offices, which also issue appropriate certificates for deer herds. A herd needs at least five years to achieve the highest certification.

decontamination

The agent is very stable in the environment. It is also not inactivated under all circumstances by most agents otherwise used for disinfection , including alcohol , formalin , hydrogen peroxide , ethylene oxide , chlorine dioxide , potassium permanganate, and phenolic disinfectants. It is extremely resistant to heat as well as UV and ionizing radiation; even after 8 hours in boiling water, it can still be infectious. The effective decontamination techniques for surfaces include exposure to strongly basic solutions (1-2 M NaOH) and those with at least 2% active chlorine (e.g. Javel water) for several hours .

Safe methods for the decontamination of rooms, buildings or open spaces are not yet known. Infected carcasses should be cremated in a facility set up for this purpose.

This makes it extremely difficult to control the CWD in the wild. Corresponding programs use a well-developed monitoring and surveillance system, hunting bans , population reductions and the capture of affected animals.

Danger to humans

The risk to humans appears to be minimal. CWD has been common in deer populations that are regularly hunted for at least 30 years. Even so, not a single case of the disease has been diagnosed in humans. As a precautionary measure, it is recommended not to shoot any obviously sick animals for consumption in the enzooty areas , to wear latex gloves when eviscerating , to avoid contact with nerve and lymphatic tissue, to disinfect all knives and other devices used to cut the prey in 50% Javel water and that Have the animal tested for CWD. These safety measures are confirmed from the results of epidemiological studies.

Individual evidence

  1. ↑ Volker Blasek: Zombie disease is spreading rapidly - first infections already confirmed in Europe. In: heilpraxis.de. February 19, 2019, accessed February 19, 2019 .
  2. ↑ (red): Deadly "zombie" disease has broken out - people also endangered. In: Westdeutsche Zeitung. February 18, 2019, accessed February 19, 2019 .
  3. ↑ First case of Chronic Wasting Disease confirmed in Europe! In: Hunter magazine. Year Top Spezial Verlag, accessed on April 19, 2016 .
  4. ↑ SL Benestad, G. Mitchell, M. Simmons, B. Ytrehus, T. Vikøren: First case of chronic wasting disease in Europe in a Norwegian free-ranging reindeer. In: Vet Res. 47 (1), Sep 15, 2016, p. 88. PMID 27641251
  5. ↑ Brent Race, Katie Williams, Christina D. Orrú, Andrew G. Hughson, Lori Lubke, Bruce Chesebro: Lack of Transmission of Chronic Wasting Disease to Cynomolgus Macaques . In: Julie K. Pfeiffer (Ed.): Journal of Virology . American Society for Microbiology, April 25, 2018, doi : 10.1128 / JVI.00550-18 (English, Journal of Virology [accessed February 17, 2019]).
  6. ↑ YH Lee, HJ Sohn, MJ Kim, HJ Kim, WY Lee, EI Yun, DS Tark, IS Cho, A. Balachandran: Strain characterization of the Korean CWD cases in 2001 and 2004. In: J Vet Med Sci. 75 (1), Jan 31, 2013, pp. 95-98. PMID 22972463
  7. ↑ T. Blasche, EV Schenck, A. Balachandran, MW Miller, J. Langenberg, K. Frölich, F. Steinbach: Rapid detection of CWD PrP: comparison of tests designed for the detection of BSE or scrapie. In: Transbound Emerg Dis. 59 (5), Oct 2012, pp. 405-415. PMID 22212828
  8. ↑ DM Henderson, M. Manca, NJ Haley, ND Denkers, AV Nalls, CK Mathiason, B. Caughey, EA Hoover: Rapid antemortem detection of CWD prions in deer saliva. In: PLoS One. 8 (9), Sep 11, 2013, p. E74377. PMID 24040235
  9. ↑ Chronic Wasting Disease (pdf) of the Canadian Food Inspection Agency .
  10. ↑ compare literature reports on CHEMICAL INACTIVATION for Prion Protein and PHYSICAL SUSCEPTIBILITY for Prion Protein .
  11. ↑ L. Waddell, J. Greig, M. Mascarenhas, A. Otten, T. Corrin, K. Hierlihy: Current evidence on the transmissibility of chronic wasting disease prions to humans-A systematic review. Review. In: Transbound Emerg Dis. Jan 30, 2017. PMID 28139079

literature

  • Chronic wasting disease. In: The Merck Veterinary Manual. 9th edition. Whitehouse Station, NJ, USA, 2005, ISBN 0-911910-50-6 , pp. 993 ff.

Web links

Commons : Chronic Wasting Disease  - collection of pictures, videos and audio files