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Aleutian Disease in Ferrets

A Complex and Devastating Disease

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Aleutian disease (AD) is not a new disease in ferrets, but it is getting more attention recently. Currently there is no treatment or prevention for this viral disease, and the progression of the disease and the biology of the virus that causes the disease is rather poorly understood. Hopefully, the recent increase in awareness of this disease will help lead to more research and perhaps an effective treatment.

The virus (ADV), which is a type of parvovirus, got it's name from the strain of mink (Aleutian) in which the virus was first detected (AD is also sometimes called Aleutian mink disease). There are several strains of AVD, and it is believed that the different strains of virus may vary in the severity of disease that they cause.

Transmission can be direct via feces, urine, saliva or blood, and also through the placenta from a jill to her kits. Transmission through the air is also possible, as is transmission through contact with contaminated surfaces (dishes, clothes, etc.). Because it is a parvovirus, the virus can survive for long periods of time in the environment.

Ferrets can carry the virus without showing symptoms (it is believed this is fairly common), but they can still transmit the virus to other ferrets. However, little is understood about under what conditions or how often virus shedding occurs and how long ferrets remain aymptomatic carriers.

The Disease

The virus is unusual in that it elicits a strong immune response (production of antibodies) from the ferret, but the antibodies produced do not neutralize the virus. Instead, antibodies are produced (sometimes in massive amounts), which can form complexes that are deposited in tissues, producing inflammation that is ultimately responsible for the progression of the disease. In addition, certain immune system cells (plasmacytes and lymphocytes) accumulate in tissues. It is actually the immune response to the virus that causes the symptoms rather than the virus directly. This is why vaccination isn't feasible at this point, because it could elicit a similar immune response. Infection with the ADV also appears to depress the immune system so that it is unable to respond effectively to other conditions so the ferrets are more susceptible to a host of other diseases as well.

AD is has often been described as a "wasting disease" characterized by chronic (long term) weight loss. A common manifestation is weakness or paralysis due to spinal cord damage, which progresses from the hind end up to the front legs. Other signs include lethargy, tarry stools (due to blood in the stool), and tremors. Occasionally the disease may cause sudden death. Organs commonly affected include the kidneys and liver.

Diagnosis

Diagnosis of AD is a challenge. A blood test called protein electrophoresis which tests for the marked increase in gammaglobulins (due to the immune response) that is sometimes seen with ADV infection, but this is not specific for ADV. Counterimmune electrophoresis (CEP or CIEP) is more specific in that it tests for antibodies to ADV, but not all ferrets that are infected will show clinical signs. In a ferret with symptoms consistent with AD and a positive blood test, AD is suspected but thorough diagnostic testing should be carried out to rule out other common ferret diseases before making a diagnosis. An ELISA test for anitbodies to ADV is now available from Avecon Diagnositics, which is said to be very sensitive and specific for ADV in ferrets. Diagnosis can also be accomplished by microscopic examination of the ferrets tissues on post mortem exam.

If a ferret with no symptoms tests positive for antibodies to ADV, it is not possible to predict if or when the ferret may exhibit signs of AD.

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