By Bruce H. Williams, DVM, DACVP
Posted: December 1, 2010, 5 a.m. EST
Courtesy of Jackie Gross
If you've got the sniffles, don't handle your ferret unless necessary.
A zoonotic disease is defined as an infectious disease that can be transferred between humans and animals. If you look online for information on zoonotic diseases of ferrets, the vast majority of diseases listed are those that are carried by ferrets and in truth, only rarely transmitted to humans. There is a significant difference between potential zoonotic disease and real zoonotic disease. The majority of discussions of zoonotic disease concern potential transfer of disease and are, in truth, cautionary — based on a perceived threat and often without actual basis in truth.
For a change, I would like to look at the flip side of zoonotic disease. Let’s see how many diseases are transmitted from humans to ferrets, and possibly dispel a few myths and misinformation in the process.
Assessing The Risk To Your Ferret
The last thing that any ferret owner wants to do is make their ferret sick. Many owners now look for the best diet, the best lifestyle, and the best way to give their ferret a stress-free and long life. When we get sick, the last thing we want to do is to pass it on to our pets. So when are they at risk?
Ferrets and humans share quite a few infectious agents, but almost never directly. For example, both ferrets and humans can be infected by Mycobacterium bovis, one of the bacteria that cause the human disease tuberculosis. However, there are no documented cases of infected humans ever transmitting tuberculosis to ferrets. The story is the same for rabies, salmonellosis, and ringworm, all diseases that both humans and ferrets can contract, but which simply don’t travel from humans to their pets.
There is a lot of misinformation out there, on both sides, from well-meaning people warning about diseases you can get from your ferret, and well-meaning ferret owners who warn of potential dangers to your ferret. But in the majority of cases, the real danger is largely imaginary.
Ferrets And The Flu
Let’s start with a real and relatively common danger — the flu. Influenza is a disease (and in truth, probably the only one) that is commonly transmitted from humans to ferrets. The ferret is one of the most susceptible animals to influenza, being able to contract every type of influenza — the old one, the new one and the one that we will have five years from now.
So it is very susceptible to your regular, everyday case of the flu. We all want to be cheered up by our pets when we are feeling sick, but a sneeze in the face of your furball during the acute phase (that first day of the flu when you are feverish, achy and have a watery discharge from your nose), and your ferret will soon join you in your sickbed.
What does flu look like in ferrets? A lot like it does in you — watery eyes, runny nose, sneezing, not wanting to eat and malaise. What is "malaise” in a ferret? Malaise means your friend is not coming out of its cage, not bouncing around the room and just basically acting "un-ferretlike.”
The biggest difference between flu in ferrets and flu in humans is the duration. We are sick for three to five days, but ferrets are sick for two to three weeks. But it is basically the same disease in both species. In ferrets, it lasts longer — imagine having the flu for three weeks! But the flu is not life-threatening in ferrets, unless their owners choose to share their over-the-counter meds with their sick little friends. Human flu medicine contains some ingredients that are toxic for ferrets, especially those containing acetaminophen, such as Tylenol. Even a small dose of acetaminophen will cause fatal liver damage in ferrets.
The best treatment for the flu is actually the best prevention — stay away from your fuzzies when you feel like you are coming down with something, and wash your hands carefully when you aren’t feeling well.
Transmission Of Other Potential Ailments
In reality, influenza is the most common potential disease that you can give to your ferret, and all other infectious diseases fall into the realm of” possible but highly unlikely.” There are a number of infectious agents that can cause disease in both humans and ferrets, but very specific requirements for transmission would have to be met. Usually, one or both of the parties would have to be immunosuppressed and ripe for infectious disease. We see immunosuppression in the very old and very young of both species, and in humans that are deliberately immunosuppressed following organ transplants, during chemotherapy or AIDS patients. In ferrets, immunosuppression may be seen in animals that are on high doses of steroids to combat insulinoma or immune-mediated diseases.
The transmission route of an infectious disease is also important. When considering infectious agents with the potential to infect both humans and ferrets, agents of the respiratory tract are those that are the most likely to jump from owner to pet (usually via coughs or sneezes, which expel viruses or bacteria). The possibility of transmission of GI infections is more remote and potential circumstances of their transmission (usually through feces) would obviously be uncommon. Finally, transmission of blood-borne agents would be the most remote as the contact of pets with their owner’s blood is highly unlikely under any realistic circumstance.
Ferrets And MRSA
At this point, a brief mention of MRSA (short for methicillin-resistant Staphylococcus aureus) should be mentioned, as it is often of concern to ferret owners. MRSA is becoming a serious health problem in humans, resulting in skin infections that are resistant to most known antibiotics. Today’s MRSA is a result of the relatively liberal use of antibiotics by MDs and DVMs in past decades, as well as this bacterium’s amazing ability to generate resistance to antibiotics over relatively short periods of time. In humans, skin infections are most common, but if the bacteria gain a foothold to the systemic circulation, life-threatening disease can result.
Ferrets (especially those kept outdoors or in unsanitary conditions) do get Staphylococcal infections, which can result in abscesses (usually skin), mastitis, and rarely systemic infections, but so far MRSA does not appear to be a problem. There are no reports in the current veterinary medicine about MRSA infection in ferrets. MRSA is most commonly a problem of humans who congregate in hospitals ("healthcare-associated MRSA”) or places where skin-to-skin contact facilitates its transmission — sports facilities, child care centers and crowded living spaces. As the primary sign of MRSA infection is a painful cutaneous boil, I’ll just leave you with the following recommendation which I think is pretty easy to follow and will keep MRSA away from your ferret in most instances: Don’t let ferrets around your painful skin boils. For now, case closed!
Ferrets And C. Difficile
There has also been a bit of discussion in ferret circles recently about a particular bacterium that affects both humans and ferrets, which goes by the name of Clostridium difficile. C. difficile is a ubiquitous bacterium that lives in small numbers in the gastrointestinal tract of most mammalian species. It is an innocuous inhabitant when the normal bacterial flora is in appropriate proportion, but may grow unimpeded if the normal "healthy” bacteria are killed off. This most commonly occurs when antibiotics are prescribed either for excessive duration, in excessive doses or both. In large numbers, C. difficile can produce enough toxin to kill off the cells of the intestinal lining, and may even be fatal. In rabbits and guinea pigs, even a single dose of some antibiotics may be enough to start this chain of events, but in carnivores, it is a fairly rare event. It is occasionally seen in humans, especially following surgery or after severe bacterial infections when high doses of antibiotics are required. Clostridiosis, however, is not a transmissible disease, and pops up only when the bacterial flora of almost any mammal is seriously "out of whack.”
This year, a lot of talk about C. difficile infection occurred following the identification of C. difficile toxin in the feces of ferrets that died from diarrheal disease. However, as everyone (humans and ferrets, and many other species) has this bacterium normally in the GI tract, very sensitive tests can often pick up levels of toxin far below that which causes problems. The diagnosis of C. difficile in animals involves not only finding the toxin in intestinal contents, but identifying the characteristic lesion it creates in the intestinal wall in autopsy samples. A positive diagnosis is achieved only when both criteria are met. In the cases this year, the toxin was identified, but the lesion was not; the final diagnosis in this series of cases was severe coccidiosis, not clostridiosis
People can make ferrets sick in a number of ways — poor nutrition, poor breeding practices, lack of exercise, and even in some cases, withholding proper veterinary care such as not vaccinating. Transmission of human diseases to our pets, however, falls far down this list. If you can remember to keep your ferrets at arm’s length when you have the sniffles, then you’ve probably covered your bases with your infectious disease.