AUTHOR: Bronwyn Dawson, D.V.M.
Dr. Domotor's Animal House Veterinary Hospital
FROM: The FerretPaw Print, March/April 2001
Ferrets and Aleutian Disease
Sometimes I think it’s something in the air.
In the last two months I have had several clients ask me about Aleutian disease in ferrets. The ferret folks on the Internet are talking about it the way they talked about ECE years ago, a local pharmacist calls to ask if I know anything about a vaccine, veterinarians who treat ferrets are dusting off their veterinary school notes to review this old but little known disease. Let me state right up front that I’m very skeptical about the supposed widespread prevalence of this disease and I do not think this is the next ferret plague. However, this is a deadly virus with no vaccine and no treatment and I think ferret owners certainly need to know as much about it as possible.
Aleutian disease is caused by a parvovirus, which was first reported in ranch-bred mink in the 1950s. The parvovirus clan is a nasty one; its divers members cause disease in dogs, cats, swine and wild mammals such as raccoons and coyotes. Like all viruses, parvoviruses can mutate into new strains and, if the mutation is great enough, have the potential to jump species lines. Those of us who owned dogs in the late 1970s remember when canine parvovirus suddenly emerged as a new disease: no vaccine, no treatment, dogs developed severe diarrhea and vomiting and usually died. Canine parvovirus, still one of the most feared puppyhood diseases, was a mutated form of feline panleukopenia, caused by the feline parvovirus.
Aleutian disease, although originally a disease of mink, now has at least one strain which is specific to ferrets. Ferrets can also be experimentally infected with the mink strains.
Unlike the acute severe disease caused by the feline and canine parvoviruses, Aleutian disease in ferrets is a chronic wasting disease. Ferrets lose weight, become quite lethargic and weak, sometimes showing neurologic signs (everything from incoordination to outright seizures).
Affected ferrets can become anemic, sometime with dark tarry stools and can develop kidney or liver failure. As stated before, antibiotics and all other treatments tried so far are ineffective. Good nursing care with supplemental fluids, feedings, even transfusions can support a ferret sick with Aleutian disease, but nothing will cure it. "Wait a minute!!" You are saying as you read this. "Neurologic signs? Incoordination? Don’t we see that with insulinomas? Anemia? Dark, tarry, stools? I thought intestinal ulcers caused that! A big liver and spleen? Couldn’t that be lymphoma? Or even heart failure?"
A resounding "yes" to all of the above, astute ferret owners! Not to mention that lethargy goes along with just about any illness that affects ferrets! Deciding that Aleutian disease is actually the cause of illness in a ferret requires some specific diagnostic tests. There are two blood tests for ferrets that look for antibodies to the Aleutian disease virus, the CEP tests used to screen mink and an Immunofluoresecent Antibody test that may be more sensitive. It is crucial to realize that a ferret can test positive on these tests yet be perfectly healthy. In fact, a positive reactor on these tests may never develop clinical disease. In the 1980s, Dr. Susan Brown, a well-known ferret veterinarian, screened over 500 shelter ferrets; 10 percent tested positive on the CEP test. Of these, only two animals subsequently developed disease signs compatible with Aleutian disease.
There is another test that can help confirm whether a sick Aleutian-positive animal is sick due to the virus or due to concurrent disease. Serum plasma electrophoresis is a blood test that separates different protein fractions in the blood according to their molecular weights. Sick ferrets with more than 20 percent of their total proteins represented in the gammaglobulins who have tested positive to Aleutian disease are quite likely to be sick because of the virus. Sick ferrets with a normal electrophoretic pattern are likely to be sick due to some other illness even if they test positive for Aleutian disease. Necropsy with tissue samples submitted to a pathologist familiar with ferret diseases is the gold standard for confirmation of Aleutian disease; however, this is not the way we like to diagnose disease in any pet.
Research is ongoing in the areas of vaccine invention and treatment of Aleutian disease. But right now, ferret owners are restricted to being familiar with the signs of this virus and distinguishing it from other ferret illnesses. The virus is shed in all bodily secretions; any ill ferrets suspected of Aleutian disease should obviously be kept separate from other ferrets.
It is believed that asymptomatic carrier ferrets do not shed virus, but even this has not been proved beyond a doubt. What is very difficult for ferret owners is the long incubation period possible with this virus and the problem of what to do with asymptomatic Aleutian positive ferrets. Mink owners cull their animals, but these are livestock to them. I would never recommend euthanasia for a healthy Aleutian positive ferret; however, I would have to caution the owner against bringing that ferret into contact with Aleutian negative ferrets. In some ways, we in California are at less risk than ferret owners in the "Free States". Because we cannot openly parade our ferrets at shows, run large-scale ferret shelters or large-scale breeding operations, we are much less likely to bring the disease home to our pets. California ferrets do not get out much, but are kept at home, for obvious reasons! This makes any hypothetical epidemic of Aleutian disease much less likely. I will not be writing any thank-you letters to California Fish and Game over this, but it is a tiny silver sliver on the cloud of ferret illegality in the Golden State.
I am glad Aleutian disease is being discussed; it is a poorly understood virus that has been completely unknown to most ferret owners. However, I caution ferret owners not to assume that any sick ferret with signs compatible with Aleutian disease actually has the disease. Lymphoma, insulinoma, eosinophilic enteritis, cardiomyopathy are all far more common among American ferrets than Aleutian disease. Remember, in our country, if we hear hoofbeats it is much more likely to be a herd of horses than a herd of zebras. A sick ferret is much more likely to have one of the common metabolic diseases than the relatively rare parvovirus.