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Chronic Wasting Disease of deer (Chronic Wasting Disease)

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Definition Signs Causes Transmission Diagnosis Treatment Prevention Complications When to see a vet Prognosis FAQ Sources Affected species

What is it?

Chronic wasting disease, also called chronic wasting disease, is a fatal neurological disease that affects deer, including elk (called moose in North America). \nIt belongs to the family of prion diseases, such as scrapie or mad cow disease. A prion is an abnormal protein that accumulates in the nervous system and gradually damages it. \nThis disease progresses very slowly, over months or even years, before the first signs appear. It is always fatal once declared. \n It has so far never been detected in Tunisia or Africa, this disease being mainly reported in North America, Scandinavia and South Korea, regions where populations of elk or wild and farmed deer live.

Key point

Always fatal disease, without treatment or vaccine, with mandatory monitoring in many countries where it is present.

Commonly observed signs

These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.

Related signs — each one links to its page:

Weight loss Reduction Behaviour change Drinks a lot Urine a lot Excessive salivation Tremors Staggering gait Difficulty swallowing Loss of sight Hiding or withdrawing Lying animal that does not get up

At first, the sick moose often shows no visible signs, with the disease progressing silently for a long time. \nWhen symptoms appear, we mainly observe a progressive and marked weight loss despite a sometimes preserved appetite, hence the name “debilitating” or “wasting” disease. \nThe animal becomes abnormally calm, moves away from the group, and loses its natural distrust of humans or predators. \nOther signs may be added: excessive thirst with copious urine, excessive salivation, tremors, staggering or disorderly gait, lowered head, hanging ears, and difficulty swallowing. \nIn the terminal phase, the elk becomes very thin, weak, unable to get up, and eventually dies, often after a complicating pneumonia.

When to consult without delay

This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.

Causes and risk factors

The disease is caused by a prion, a misfolded and abnormal protein that builds up in the brain and nervous system. \n Unlike a bacterium or a virus, the prion is not a living organism: it acts by modifying the shape of neighboring normal proteins, which also makes them abnormal and non-functional. \nThis progressive accumulation destroys nervous tissue, which explains the neurological disorders and weight loss characteristic of the disease.

Moose living in areas where the disease is already present in other wild cervids (deer, elk, reindeer) are most at risk. \nThe high animal population density, gathering points around food or water points, and the movement of animals between regions favor the spread. \n Breeding in captivity or in enclosures with sustainably contaminated soil is also a significant risk factor.

Transmission

Transmission occurs mainly between deer, through direct contact with an infected animal, or indirectly through the environment contaminated by saliva, urine, feces or carcasses of sick animals. \nPrions are exceptionally resistant and can persist for a very long time in soil and pastures, making eradication very difficult once an area is contaminated. \nThere is currently no evidence of natural transmission to humans, but health authorities recommend as a precaution never consuming the meat of an infected or suspected deer.

Diagnosis and care

Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.

There is no reliable test to diagnose the disease in living animals in routine practice. \nThe definitive diagnosis is based on the examination of the nervous tissue, in particular certain ganglia and the brain stem, carried out after the death of the animal in a specialized laboratory. \nFaced with an elk presenting unexplained progressive weight loss associated with behavioral or gait disorders, the veterinarian will mention this disease especially in regions where it is already known, and will first rule out other more frequent causes.

Treatment

There is no curative treatment. Management is limited to comfort care for the animal in captivity, while awaiting the inevitable progression towards death. \nIn wild or farmed populations, management essentially consists of stamping out affected or suspected animals, in order to limit the spread.

Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.

Prevention

There is no vaccine or preventive treatment against this disease. \nPrevention is mainly based on monitoring wild and farmed populations, with post-mortem tests on animals slaughtered or found dead in risk areas. \nLimitation of the movement of live animals between regions, the ban on artificial feeding which concentrates animals, and careful management of carcasses contribute to limiting the spread. \nIn areas never affected like Tunisia, vigilance focuses mainly on the control of imports of animals or material of deer origin from infected areas.

Possible complications

The progression is always towards extreme weakening, severe weight loss, and death, often precipitated by pneumonia linked to false swallowing or by general exhaustion. \nCollectively, the presence of the disease in a wild population permanently compromises the health of the entire herd and complicates wildlife management in the region.

When to see a veterinarian

A captive moose loses marked weight without an obvious dietary cause.

The animal shows an unusual change in behavior, becoming unusually calm or isolated.

He presents with a staggering gait, tremors or excessive salivation.

He has difficulty swallowing or gradually refuses to eat despite an apparent appetite.

A moose is found dead without apparent cause in an area where the disease has already been reported in deer.

Prognosis

The prognosis is always poor: the disease is invariably fatal once symptoms appear, generally within a few weeks to a few months. \nNo cure is possible at this time.

Frequently asked questions

Can this disease affect humans?

To date, no natural transmission to humans has been proven. As a precaution, it is recommended never to consume the meat of a sick or suspect deer, and to have animals hunted in risk areas tested.

Is the disease present in Tunisia?

No, it has never been detected in Tunisia or elsewhere in Africa. It mainly affects North America, Scandinavia and South Korea.

Can a moose be vaccinated against this disease?

No, there is no vaccine or treatment available. The only possible protection is through monitoring and limiting the spread between animals.

How does a moose get this disease?

By direct contact with an infected animal or by an environment contaminated by its saliva, urine, faeces or carcass. The responsible prion can persist for a very long time in the soil.