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Coronavirus Infection In Your Ferret

Ron Hines DVM PhD

FERRET CORONAVIRUS CANNOT GIVE YOU HUMAN CORONAVIRUS COVID-19.

One thing you can count on when dealing with any coronavirus is that the problems they cause will be ever-changing. That is because coronavirus are experts in their abilities to mutate, recombine, jump from one species to another and redirect the cell types that they attack. (ref1, ref2

In March of 1993, pet ferrets and those in breeding farms and shelters along the United States East Coast developed foul-smelling, watery or mucous diarrhea. The stool they passed had a greenish color and contained grainy material that some thought resembled birdseed (actually it was shreds of intestinal lining). The disease appeared to be highly contagious. Some referred to it as “green slime disease”.

This disease had probably been brewing in domestic ferrets for quite some time before the 1993 epidemic. But the number of ferrets affected then led researches to delve more deeply into the cause. In 2000, researches reported that a coronavirus appeared to be the underlying pathogen and gave the disease the name epizootic catarrhal enteritis (ECG). Others refer to it as Ferret Enteric Coronavirus or FRECV. 

This wasn’t the first time a disease like this had occurred. Mink ranches in Scandinavia, North America, the USSR and China had been dealing with an almost identical coronavirus diarrhea problem since at least 1975. (ref)  If and when the coronavirus jumped from mink to ferrets is something we still do not know. However ferrets and mink are so similar biologically that all it would have taken was co-mingling the two species at some breeding facility.

Ferrets that develop ECG/FRECV show little interest in food or activity. A period of vomiting and diarrhea were the prominent signs – with a steady recovery over a week or two. The disease was more likely to occur in multi-ferret households, breeding facilities pet shops and ferret rescue facilities because virus transmission there was easier and stress on the animals greater. In those situations, it was not uncommon for most or all of the ferrets to become ill. But only a tiny number of ferrets died. The few that did were generally older ferrets in which it was never confirmed that ECG was the primary cause of their death.

But then in 2004, a remarkable and worrisome thing happened. A number of ferrets began exhibiting symptoms quite similar to those seen in feline infectious peritonitis (FIP) in cats. When ferrets developed this new disease it was always fatal. FIP is an always-fatal disease of cats and it too is caused by a coronavirus. Suspiciously, it is also caused by a mutation of a feline intestinal coronavirus that causes transient mild symptoms if any at all in cats. Five of the affected ferrets were females and four were males. Eight had been purchased at pet stores. Three were bred in New Zealand, one in the Netherlands and one in Spain. This new disease was given the name of Ferret Systemic Coronavirus (FRSCV) because the whole body system of the ferret was affected – not just its intestines. (ref) The average age of the ferrets that develop this disease is about 11 month.

It is apparent that a lot of healthy ferrets carry coronavirus as well as a ferret hepatic virus that has not yet been linked to any disease. (ref

Are These One Or Two Different Virus?

They are obviously different in their construction in certain ways since they affect ferrets differently. But since it is the interplay of the ferret’s own immune system that is doing most of the damage when it responds to the virus, it could well be that certain ferrets are more prone to this damaging response than others. We veterinarians just don’t know.

One study found the more pathogenic form of ferret coronavirus was more similar to the coronavirus of mink than it was to the less pathogenic coronavirus of ferrets. (ref Deciding when a virus has changed enough to becomes a “new” virus is always debatable. (ref)

What Are The Symptoms Of The Rarely-Fatal Intestinal Form Of Coronavirus (FRECV / ECE) That I Might See In My Ferret?

The common story goes like this: A young ferret that appears healthy is introduced into an existing group of ferrets. A few days to two weeks later one or more of the older ferrets looses interest in its food, probably vomits and begins producing greenish foul smelling diarrhea. With time, it becomes dehydrated (water is lost in the diarrhea and the ferret has no interest in drinking). It looses weight. Over a month or so, it slowly recovers. Cases very greatly in their severity. Some ferrets recover much more rapidly than others. The severer cases represent the “green slime disease” that ferret clubs talk about. When a ferret does not recover from this disease, it is generally because it has other underlying health or nutritional issues and/or bacteria have taken advantage of its weakened condition.

What Might Be My Veterinarian’s Findings In This Milder Form Of Ferret Coronavirus Disease?

There are no specific laboratory tests that confirm ECE in ferrets that I know of. I suppose that some larger laboratories could identify the coronavirus in your ferret’s stool. But I already mentioned that a lot of healthy ferrets carry this virus as well.

These ferrets will be dehydrated if diarrhea and vomiting is severe. That in itself will change many of your ferret’s labwork values because as the ferret’s blood becomes more concentrated and its blood acid to base balance changes. Blood results change. But that occurs in every disease that causes vomiting and diarrhea.

X-rays when these pets are significantly ill might show mild to moderate ileus. X-rays might also show hazy definition of the shadows of your ferret’s abdominal organs due to edema fluids generated by inflammation.

So your veterinarian will probably make his or her diagnosis based on excluding other possible causes. That is, your vet will attempt to eliminate the other possible causes of diarrhea and vomiting in ferrets: ingestion of foreign objects or toxins, IBD, intestinal lymphoma, campylobacter, helicobacter , salmonella, parasites, etc. Read more about those issues here.  

It is quite unlikely that your veterinarian would attempt to do this because of the risk, specialized apparatus required and small size of ferrets; but should one peer at the lining of your ferrets intestine he/she would notice that the intestinal lining was reddened and inflamed. Should a small snippet of that intestinal tissue be examined under a microscope, lymphocytes numbers would probably be found in excess and intestinal villi blunted. (ref

How Might My Veterinarian Treat This Milder Form Of Coronavirus Disease?

The most helpful treatment to aid your ferret in getting well is subcutaneous fluid therapy and medications that line and sooth the intestinal lining such as kaolin-pectin or sucralfate. Antibiotics are also indicated to prevent secondary bacterial infections. (ref

What Are The Symptoms Of The Usually Fatal Systemic Form Of Coronavirus (FRSCV) That I Might See In My Ferret?

The much more serious systemic form of Coronavirus disease often begins much the same as the less serious intestinal (enteric) form. Greenish diarrhea is common. But it often progresses to contain visual or hidden blood (hematochezia). That is accompanied by a lack of appetite, major weight loss and dehydration. There is a lot of abdominal pain associated with this disease. It is not uncommon for these ferrets to grind their teeth. One can often feel (palpate) lumps in these ferrets’ abdomens. One might mistake those lumps for objects the ferret swallowed (in reality they are granulomas) – clumps of immune system cells attacking ferret cells that were damaged by the virus. It is not unusual for these ferrets to have pale gums since many become anemic. These ferrets will occasionally have enlarged superficial lymph nodes (just under their skin) but that is quite uncommon. Lymphoma is the most common cause of enlarged lymph nodes in ferrets. A few infected ferrets exhibit signs of brain or nerve damage as well. The average survival time after symptoms first begin is ~2.5 months.

There is a subset of ferrets that are brought to veterinarians because their owners noticed an eye problem. The cornea of one or both of the ferret’s eyes is seen to have milk-like spots. That problem that might simply be brushed off as a scratched cornea resulting in a corneal ulcer. Perhaps overgrown toenails? But generally in their discussions with their veterinarian it becomes apparent that the pet has other health issues as well. Some of these eye problems have turned out to be a manifestation of the systemic form of coronavirus disease. (ref) Eye problems in ferrets have many causes. Your veterinarian will be ruling out things like corneal scratches, misplaced eyelash hairs (distichiasis), sensitivity to the ferret bedding you use or diseases such as canine distemper  or human influenza.

What Tests Might My Veterinarian Run And What Might Be The Results In The Much Worse Systemic (FRSCV) Form Of Coronavirus Infection?

Because so many organ systems are affected by the systemic form of coronavirus disease, laboratory and in-office blood analysis from these ferrets show many abnormalities. The stress of the disease causes some ferrets blood sugar levels to be high (hyperglycemia). Liver enzyme levels tend to be higher than normal as well (elevated AP, ALT, GGT). It is not unusual for the pet’s CK level to be elevated – evidence of muscle damage. Failure to eat often causes their blood albumin protein level to be low. Systemic inflammation causes their blood globulin level to be high. Some affected ferrets have lower than normal blood calcium levels as well. The majority are also anemic. Some have elevated white blood cell counts.

While x-rays of the abdomens of ferrets suffering from the milder intestinal (enteric) form of coronavirus disease show signs of intestinal inflammation, x-rays from this much more serious form often show an enlarged spleen, as well as abnormal tissue masses scattered throughout the abdominal cavity and the organs that occupy that space (liver, kidneys, lymph nodes, mesenteries). These masses are lumps and clumps of immune system cells (pyogranulomatous inflammation). (ref) Autieri2015.pdf These are the same lesions seen in the “Wet” form of coronavirus FIP in cats. However ferrets rarely if ever produce the free fluid that bloats feline abdomens in FIP disease. When a ferret with this severe form of coronavirus disease (FRSCV) is autopsied there is really no other disease one could confuse it with. The closes thing I have seen to is disseminated tuberculosis in monkeys.

What Kind Of Treatment Can My Veterinarian Offer My Ferret For This Severe Disease?

When I have satisfied myself that your ferret is suffering from the severe form of coronavirus disease, I encourage my clients to let me euthanize the pet. I believe that that is the kindest thing you and your veterinarian can do for the pet you love. But when I am not certain of the diagnosis – just quite suspicious – I usually suggest a week or two of supportive care to see how things develop.

Many of these ferrets come in dehydrated. After your veterinarian gives them subcutaneous and intravenous fluids, many will perk up temporarily. Most veterinarians will place them on antibiotics as well. They know that antibiotics are not going to cure viruses, but they do give protection against bacteria that might be taking advantage of the ferret’s weakened situation. Prednisone (corticosteroids) tends to perk these ferrets up too. It might even get them interested in food – particularly when it is a meat-based treat and warm. But both effects are temporary. Sucralfate might help coat and sooth inflamed intestines. Other vets give Tagamet® or Zantac®. Some give Cerenia® or Reglan® to control vomiting. Others give blood transfusions. Some give probiotics such as Fortiflora®. Some give vitamin B12 or B complex injections. Some vets give them injections of immunostimulants. I have no faith in them but some veterinarians do. Other vets go the opposite direction and give the ferrets immunosuppressants (I mentioned prednisone, a corticosteroid). That is because immune system over-reaction to the organ damage coronavirus causes in cats is thought by some to account for much of the later organ damage).

These ferrets can be tube fed and their blood electrolyte imbalances (eg low blood potassium, low blood calcium) can be corrected. The average survival time when these heroic treatments are administered is about 2 months. I personally see doing these things as quite cruel. If your ferret could talk to you I think it would agree. In systemic coronavirus disease, I believe that these treatments simply insure a lingering death at the expense of the ferret and its owner.

Might There Have Been A Recent Treatment Breakthrough?

I have an acquaintance, Dr. Niels Pedersen. We are of the same vintage. Dr. Pedersen did pioneering work in the discovery of the feline immunodeficiency virus of cats as well as the cat form of coronavirus disease when the virus mutates to cause feline infectious peritonitis (FIP) – a disease that mimics the severe form of coronavirus disease in ferrets. Dr. Pedersen teamed up with virologists at Kansas State University who already knew that certain protease inhibiting drugs screened for their effects against Ebola virus also inhibited coronavirus. They found that two of these drugs “cured” a number of cats suffering from FIP coronavirus – a previously incurable disease.

In 2018 it was reported that these same compounds (protease inhibitors) are effective against the coronavirus of ferrets too. (ref)  Read about those anti-viral medications here and here. You would have to contact them directly to learn if those compounds are available to you. Those that offer the most hope for cats are not readily available. However cat owns have found ways to obtain them. If you go down that road let me know and I will post your experiences on this webpage.

Are There Steps I Can Take To Protect My Ferret From Coronavirus In Both Its Forms?

Ferrets are always safer when they are kept isolated from other ferrets or only exposed to an isolated and stable home ferret group. Avoid ferret meetups, shows, pet stores, etc. When you obtain a new ferret, don’t introduce it to the other ferrets you already have for 4 weeks. During that period of isolation check its general health and weight regularly. A veterinary exam that finds no evidence of ill health is not a substitute for a period of isolation after purchase. It is quite rare that a veterinarian would identify an exposed pet during the disease’s incubation period or its first day or two of virus shedding.

Buy your ferrets from reputable sources. A medium size breeding operation can mean more opportunities for disease transmission. The most conscientious ferret sources are often the small ones and the very large ones.

There are polymerase reaction (PCR) tests that are highly sensitive in detecting coronavirus in your ferret. A 2017 article found that the coronavirus causing the milder intestinal form of disease (the FRECV coronavirus) was present in 84% of the ferrets tested while the systemic FRSCV form with the potential to kill was present in 23.8% of what appeared to be healthy ferrets. I listed that article before but you can read it here too. 

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