Heartworm (Dirofilaria immitis) is a parasite that affects several types of animals, most commonly cats, dogs, and ferrets. This parasite is transmitted when an infected mosquito bites your pet. Unfortunately, prevention of this issue in ferrets has long been overlooked. However, each year, several cases in cats and dogs test positive in the greater Montreal area and Montérégie. Studies indicate that ferrets have infection rates similar to those of dogs, and even higher than those of cats. It is believed that adult heartworms can live in a ferret's heart for up to two years. Due to the small size of a ferret's heart, just one or two worms can be catastrophic (see data below). Both indoor and outdoor ferrets are at risk. Be aware that more than twenty different mosquito species can carry heartworms, and several of them can develop inside our homes.
Data from a recent heartworm conference at Cornell in the United States:
- If you feed 100 Dirofilaria larvae (called L3) to 10 dogs, you will have 10 dogs with 70-80 adult heartworms in six months.
- If you feed 100 larvae to 10 cats, you will have 7-8 cats with less than 10 adult heartworms.
- Finally, if you feed 10 ferrets 25 L3 larvae, 50% of the ferrets will die quickly.
This is simply to illustrate to you that ferrets are very sensitive to this parasite and that we cannot take it lightly.
What are the symptoms of an infected ferret?
The signs vary greatly depending on the degree of infection: loss of appetite, difficult or rapid breathing, abnormal lung sounds, cough, weakness, ascites (accumulation of fluid in the abdomen), pleural effusion (accumulation of fluid in the chest), heart murmur or other heart problem, and sometimes even death.
What tests are available?
A blood test performed at our hospital is available and can diagnose the majority of cases. Sometimes a chest X-ray or cardiac ultrasound can also help.
How do we prevent heartworms in ferrets?
First, you need to make sure that the ferret is not a carrier of heartworm using a blood test (“Snap Elisa test”). When the negative result is confirmed, a preventive medication is used for 6 months (starting around mid-May until mid-October).
The protocol we use is as follows: a clinical test is carried out the first year, then it is carried out every two years. There are two conditions required to take the test every two years. First, you must have given all doses of the medication to be sure that your ferret has not been infected with Dirofilaria. Second, your ferret must be up to date with the annual review. If these two conditions are not met, then it is best to retest the following year.
Why is prevention important?
The reason is simply that prevention is much simpler and less dangerous than treatment. Unfortunately, heartworm treatment is problematic because the mortality rate is relatively high compared to cats and dogs.
What medicine is used to treat heartworms?
Selamectin (Revolution) is the most commonly used medication at AnimaPlus. It is both safe and effective in ferrets. Other alternatives exist but they are less effective.
If you would like more details, do not hesitate to consult one of our technicians or one of our veterinarians.