Heartworm in Ferrets

How real are the risks of a ferret catching heartworm?

Ferrets are funny creatures on so many levels. The antics of these fur-friends can amuse and entertain for hours; playful and friendly they are arguably a much under-rated pet. But they’re also funny in the ‘peculiar’ sense of the word, because of their health conditions they’re susceptible to.

For example, just like dogs, ferrets are vulnerable to distemper. And just like dogs…and cats…they can acquire heartworm. Indeed, ferrets are just one of 30 animal species who are susceptible to heartworm infections.

The Risk to Indoor Pets

Many owners of indoor pets (be they ferrets or cats) can be lulled into a false sense of security with regards to heartworm. The argument goes that since they are indoors, the risk of exposure to infection is low. However, this is flawed logic when it comes to heartworm.

Heartworm is spread via mosquito bites. Anyone who has ever been annoyed by a buzzing mosquito at night will know that insects can and do get indoors, no matter the lengths to stop them. Proof of this is the heartworm infection rate in indoor cats, which is estimated to be as high as 25% in some areas.

To state the facts baldly, keeping an indoor pet is not protection enough against heartworm.

How Do Ferrets Catch Heartworm?

Heartworm is a parasitic worm that is spread from host to host via feeding mosquitoes. In simple terms, a mosquito feeds on infected blood and ingests the larval form of heartworm. This is then transferred to the next animal the mosquito feeds on.

Once the larval stage enters the bloodstream, it uses blood vessels as a superhighway and migrates to the lungs and heart. Over several months the larvae mature into adult worms. These then cause a physical blockage that clogs the heart and major blood vessels, sending the host into circulatory failure.

The Big Picture: Heartworm in Ferrets

Heartworm infection has different characteristics in different species. For example, dogs tend to host high numbers of adult worms, whilst in cats, it may be just a handful. Ferrets sit somewhere in between with around 14 – 15 adult worms being typical, which unfortunately is more than enough to damage the heart and circulation.

Signs to be Alert For

• Poor appetite
• Lack of energy
• Coughing
• Breathing difficulties
• Weight loss
• Vomiting
• Blue gums
• Swollen belly
• Noticeably yellow-orange urine
• Loss of use of backend

Blood tests to diagnose heartworm infection look for markers linked to the presence of adult worms. This test is relatively reliable in ferrets and gives fewer false results than in cats. In addition, the vet may want to ultrasound a ferret which tests positive, to assess how many worms are present and the amount of damage already done to the heart.

However, once the problem is diagnosed, treatment can be tricky.

Treatment Ferrets with Heartworm

Treatment is difficult because the main drug (Melarsomine) used in dogs is not safe for ferrets. Yes, the drug will get rid of the adult worms, but there’s also a danger to the ferret…talk about throwing the baby out with the bath water!

Instead, the vet may opt to stabilize the ferret and support his organ function. This can include drugs such as:

• Diuretics: To shift fluid retained in the chest and belly
• Pimobendan: To help the heart pump more effectively
• ACE inhibitors: To make it easier for blood to flow in the vessels
• Steroids: To reduce lung damage due to the migration of larvae
• Antibiotics: To fight complications such as pneumonia, caused by dying larvae.

Once the patient is in the best health possible under the circumstances, the vet may suggest trying to get rid of the adult worms. Unfortunately, there are no products licensed for this purpose in ferrets, which means all treatments are a calculated risk. Those therapies that ferret-vets find to be most safe and effective include the use of ivermectin or moxidectin based products.

Therefore taking everything into account, much like for cats, prevention of heartworm infection in ferrets is essential. But were you even aware there was such a thing for ferrets?

Prevention of Heartworm in Ferrets

As a responsible ferret owner who wants to protect their pet, you do have options.

In terms of preventative products, speak to your vet about what they recommend. The likely options include using a cat heartworm preventative with the dose scaled down to ferret size or monthly oral treatments with ivermectin in products such as Advocate for kittens. Whichever option you choose, be sure to apply it monthly (or as directed) so there’s no gap in protection.

Don’t overlook the risk of pet to pet (via mosquitoes) spread, since an infected dog in the home could be a hazard to the ferret. Thus treating all the pets in the household gives more global protection.

Also important is to reduce the access of mosquitoes in and around your home. This means checking the yard and surrounding areas and removing sources of stagnant water that could provide mosquito breeding grounds. By getting rid of perfect mosquito habitats you lower the burden of insects in your local area and reduce the numbers posing a risk to your ferret.

However, this isn’t the whole story as mosquitoes are so light they can be blown considerable distances. With this in mind consider attaching mosquito netting over your ferret’s housing and run, so there’s a physical defense against those pesky mosquitoes.

All of which brings us back to prevention, so do your ferret a favor and discuss options with your vet today.

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