Deborah Cottrell, DVM
Although it’s important to be familiar with the common health problems in ferrets, you also need some knowledge of the uncommon ones. This is by no means a comprehensive list, but the ailments mentioned are those I consider to be the 10 uncommon health problems of ferrets that are encountered most frequently.
1. Prolapsed Rectum
A new ferret owner gets a kit (baby ferret) only to find it has diarrhea and, within a few days, a prolapsed rectum. This is caused by a condition known as proliferative colitis and is due to a bacterial infection often contracted when ferrets are only a few weeks old. Some people might suspect the epizootic catarrhal enteritis (ECE) virus because it causes diarrhea, but it is not usually the culprit in rectal prolapse.
It causes severe inflammation of the lower intestinal tract and can even cause death if untreated. It is also possibly related to the stress factors young ferrets experience when they are de-scented, thus making the rectal area more susceptible to infection. The incisions that result from de-scenting may predispose the rectum to prolapse.
The bacterium Lawsoni intracellularis causes a similar condition in many different species, including foals and baby pigs. It’s unclear if the organism can pass between species, but it seems doubtful. It can cause long-term damage to the lining of the intestine, just as the ECE virus can. It is possible for an individual to be infected with both the bacteria and the virus at the same time.
If a young ferret is having diarrhea and is straining to pass stool, the bacterium L. intracellularis may be to blame. It can sometimes be difficult to distinguish this from other diarrheas, but the characteristic straining is what can cause the rectum to prolapse.
When this occurs, the prolapse itself must be treated surgically and the infection treated. Several antibiotics can be effective against this organism, but chloramphenicol is generally considered the best.
2. Aleutian Disease Virus (ADV)
I have included ADV in the list of uncommon diseases because, even though it’s fairly well-known and scary, it is not currently present in high numbers in the pet ferret population. There have been spikes of the disease in groups of ferrets for the last 20 years, but the overall incidence appears to be low. Outbreaks appear to occur every few years, followed by long periods of little to no activity.
ADV is part of the parvovirus family, but is not at all like parvo in dogs. The closest analogy is probably the feline immunodeficiency virus of cats. The virus suppresses the immune system and causes the animal to be susceptible to many other diseases and syndromes. Ferrets with active ADV infections may die of kidney or liver failure.
The virus is spread by direct contact with bodily fluids and can be elusive to diagnose because the virus may be dormant for very long periods of time. Testing is problematic, because many ferrets with ADV will test negative. Even if a ferret tests positive, there’s no way to predict whether a specific ferret will ever actually get sick due to ADV.
The only way to be sure your ferret is never exposed to ADV is to never let him play with ferrets he does not live with and never take him anywhere he may encounter other ferrets. Although this is medically sound advice, it’s not very practical. It would eliminate the ferret shows, gatherings and events that are a big part of the ferret “fun” factor.
3. Canine Distemper
Canine distemper is a virus of the morbillivirus family. It is a highly infectious, airborne disease that has an extremely high mortality rate and can affect any species of canine; mustelids, like ferrets, weasels and otters; procyonids, such as raccoons and coatimundis; and certain bears, such as pandas.
In ferrets, the disease follows a very predictable course and the outcome is always certain death. All ferrets should be vaccinated against canine distemper. There are currently a couple of long-term duration-of-immunity studies under way to give us good data on how frequently we need to vaccinate, but I believe there is no question all ferrets should receive multiple sets of vaccines as kits, and at least one booster in their adult life. I currently recommend boosters every other year unless the ferret is vaccine-reactive.
The only USDA-approved vaccine for ferrets is Merial’s Ferret Distemper vaccine. It is a recombinant type of vaccine, which is a relatively new technology. It is not possible for a recombinant to cause disease, and it is not associated with any of the immune-related conditions sometimes blamed on modified-live vaccines.
I believe the trend not to vaccinate ferrets may be paving the way for a major outbreak of distemper sometime in the future, turning it from a rare disease into a common one. If this happens, it may be potentially devastating for populations of raccoons, skunks, foxes and wolves, as well as domestic animals.
A small number of individuals can remain unvaccinated and still be protected by the “herd health” effect. This means that when the animals around an unvaccinated individual are vaccinated, the unvaccinated animal is insulated against infection. The more animals that go unvaccinated, the smaller the circle of protection becomes, until it eventually collapses and large numbers of animals are infected.
In the first week of clinical symptoms, distemper can be impossible to distinguish from influenza virus. Thick, yellow-green discharge from the eyes and nose are characteristic of both. In the second week, however, ferrets with influenza will begin to get better, and those with distemper will get worse. The virus invades the nervous system, causing intractable seizures, and death follows within the second week.
4. Acetaminophen Toxicosis
This is not as rare a problem as we would like it to be. The most common scenario in ferrets is when people use a medication like liquid children’s Tylenol, which contains acetaminophen, on a ferret that has sniffles, allergies or suspected flu. One single, small, oral dose of acetaminophen or one pill will kill a ferret.
Acetaminophen toxicity works in two ways. It can bind with red blood cells in place of hemoglobin, producing a condition known as methemoglobinemia, where the red blood cells can no longer carry oxygen. Most ferrets will die from this condition without ever getting to the second stage of poisoning, in which the liver completely shuts down.
In one case, the owner of two young, healthy ferrets lost them to liver failure within 48 hours of them eating a pill containing acetaminophen that was unknowingly dropped on the floor.
5. Heartworm Disease
Ferrets are not a natural host for heartworms, but they can contract them from mosquito bites. We encourage ferret owners to use heartworm preventive even though most ferrets live indoors. In any area of the country where heartworm disease is common in dogs, it also occurs in ferrets. In laboratory tests, ferrets have been shown to be more susceptible than cats to infection with heartworms.
If you live in the southeastern United States, which is considered to be Heartworm Central, your ferret should be on preventive year-round. Bear in mind that a mosquito has a travel range of about five miles, so if there are any dogs, coyotes, wolves or foxes within five miles of your ferret, one mosquito bite can transmit enough heartworm larvae to kill a ferret.
Heartworm prevention can be provided in several forms. The ideal situation would be to use a preventive like Advantage Multi, because it provides protection against other parasites as well and has been tested for use in ferrets. However, in households where there are more than three ferrets, that can get expensive, so a tried-and-true method I use is a diluted form of liquid ivermectin. Consult with your veterinarian if you wish to use this method, as dilution must be exact and a specific chemical must be used.
>Ferrets have an extremely wide range of susceptibility to flu viruses. For example, they are susceptible to human influenza A, but several other types of human flu have very little effect. Several strains of avian flu can cause severe disease and even death, but several others have no effect. We have little data on swine flu, but what we know suggests that although only about 10 percent of exposed ferrets will actually get it, it can be very serious in those that do.
We know swine flu and human flu are both becoming fairly common in the United States, and it may be that avian flu is not far behind.
TamiFlu is a well-tested treatment for flu, but it is not effective on all strains. To complicate matters, it can be very difficult to acquire. If your ferret gets the flu, TamiFlu is the best choice to treat it, if you can get it through your veterinarian to know the proper use and dosage.
If you come down with the flu, have your ferret stay with a friend for the first few days while you recover. As a general rule, you can infect others for the first five days that you show symptoms.
This is a term combining the two words “pyo” meaning “pus” and “thorax” meaning chest. It literally means a pus-producing infection in the chest. It is unusual, but can happen to ferrets because they eat so many strange objects.
In many cases, pyothorax develops when a sharp edge of something (like a ragged piece of hard rubber) punctures a hole in the esophagus as it makes its way to the stomach; or, it can get stuck in the esophagus and sit there until it wears a hole in the tissue. Once that happens, infection begins to leak into the chest cavity and can build up until the ferret is very, very sick.
In the early stages, symptoms can mimic heartworm disease or a tumor of the thymus in the chest cavity.
In one case, a ferret was presented barely able to breathe, and died shortly after arrival to the hospital. When we did the postmortem exam, we found the entire chest cavity full of pus due to a small piece of toothpick he had eaten, which then lodged in the esophagus and eventually punctured it.
8. Non-Adrenal Bladder Infections
Most everyone with any experience in adrenal gland disease knows that male ferrets with the disease can have serious prostate problems. The prostate responds to the high hormone levels by swelling up and producing large amounts of fluid. In some cases, the prostate can become so large it looks like a second urinary bladder and can put enough pressure on the urethra to prevent the ferret from urinating. This can cause a ruptured bladder or the ferret can die of renal failure. There may or may not be a bacterial infection associated with it.
In female ferrets, a similar process occurs. When adrenal sex hormones cause enlargement of the nipples, labia and cervix, this allows bacteria to ascend up the urethra to the bladder, thus causing infections. This rarely happens in ferrets without adrenal disease.
In my experience, bladder infections in ferrets of either gender that are not related to adrenal tumors are unusual. If your ferret is diagnosed with a bladder infection, it should be a huge red flag that adrenal disease is probably present.
Epizootic catarrhal enteritis, known as ECE or Green Slime Disease, was first diagnosed in approximately 1993 (per Dr. Bruce Williams). It is caused by a virus from the coronavirus family and is thought to have originated in mink farms.
It marched its way across America causing severe disease and death, especially in older ferrets that were first exposed to it. Once a ferret has survived ECE, he can shed the virus for at least six months and possibly longer. Once the virus has invaded the intestines, it can result in permanent damage that can leave the ferret susceptible to other intestinal problems that may lead to diarrhea later.
ECE could actually be included in both lists of “common” and “uncommon” diseases. It is now so commonly present in every ferret breeding facility that almost every pet ferret sold has been exposed before arriving at a pet store or shelter. Most young ferrets have already fought off the virus and appear healthy by the time they are purchased. Occasionally, we will see kits come from the pet store still experiencing diarrhea and loss of appetite, but most of them respond to minimal treatment.
For the most part, the days are gone when a new, apparently healthy ferret is brought into a household and the older ferrets immediately fall seriously ill. This is because the virus has now been around so long that almost all living ferrets have already been exposed in their early lifetimes. The worst cases we usually see now are ferrets that have recurrences of diarrhea that may last a week or two. This may be related to damage done early on by ECE, or it may be due to a number of other causes. If your ferret has diarrhea for more than three days, make an appointment with your veterinarian.
Worldwide, dogs are far and away the leading carriers of the strain of rabies virus that infects people. In the United States, the very few people who have died of rabies have mostly contracted it from bats. However, the wild raccoon and coyote populations of the United States have a very high percentage of animals infected with rabies. Only about 0.5 percent of bats are estimated to have it, where up to 20 percent of raccoons in some areas have it. Fortunately, only about 10 cases of rabies in ferrets have been reported in the last 50 years.
Up until 1991, if your ferret bit someone in the United States, it would have to be killed and tested for rabies, because there was not a recognized vaccine nor was there an accepted quarantine period. Many ferret owners still remember those days and how many innocent ferrets were killed, and none of us want to go back to those days. In 1991, Merial introduced the first (and still only) approved rabies vaccine for ferrets. Rabies vaccination for ferrets is now required in virtually every state.
This article originally appeared in the Ferrets USA 2010 annual magazine. Dr. Cottrell founded West End Animal Hospital in Newberry, Florida.