The bad news: Heartworm disease can be fatal to dogs, cats, & ferrets. The good news: You can protect your pet from this disease.
âItâs a preventable disease, which is why itâs so frustrating as a practitioner when you see a case,â says Melanie McLean, D.V.M., a veterinarian at the U.S. Food & Drug Administration (FDA). Treatment can be hard on animals, & McLean says itâs much easier & healthier for the pet to prevent the disease in the first place.
Heartworms are carried by infected mosquitoes that transmit parasitic worms that grow in the arteries of the lungs and heart of dogs, cats, & other species of mammals, including ferrets. The heartworm larvae enter the bite wound & move through the pet’s body. They can grow up to 12 inches long.
The disease is not contagious from one pet to another, and heartworms in humans are very rare.
Use Heartworm Prevention Medication Year-Round
The FDA has approved several heartworm prevention medications for dogs & cats, but only one, to date, for ferrets. Treatment can vary, as oral, injectable or topical, depending on the animal species, but they all target heartworm larvae, not adults.
Thatâs one reason veterinarians often recommend that pets receive heartworm prevention medication all year long. Although there are a fewer number of mosquitoes in the winter, there is still a risk that an animal could contract heartworms if the owner stops giving medication during this season.
âYou never know when the first mosquito is going to come out, or when the last mosquito is going to die. Heartworms have been reported in dogs in all 50 states, & just because you live in a state with a colder climate doesnât mean that your animal is safe,â McLean warns. Animal owners who stop giving heartworm prevention medication during the winter run the risk of their animal contracting heartworms. If the animal becomes infected & you later resume giving the heartworm prevention medication without testing, you may be putting your pet in danger. The preventive medication can kill so many microfilariae (the offspring of adult, female heartworms) at once that it could shock the animalâs system, with potentially fatal results. Also, the prevention medication will not kill adult heartworms, which will continue to reproduce.
Testing for Heartworms is Important
Be sure to have your veterinarian test your dog before you start using a heartworm prevention medication. (Prevention medications for dogs come in all three forms: oral, topical, & injectable. Talk to your veterinarian about which is best for your dog.) Dogs that have heartworms may not show symptoms right away, & your veterinarian can easily test your dog with a simple blood test.
& even if youâve kept your dog on a steady regimen of preventive medication, your veterinarian should test for heartworms on a yearly basis. No drug is 100 percent effective, & you want to make sure the drug is working. Moreover, owners often forget to give the prevention medication for a month or longer.
Cats & Ferrets: Indoor Pets Need Heartworm Prevention Medication, Too
Even if your pet rarely or never goes outside, she should still take a heartworm prevention medication. Mosquitoes that transmit heartworms can easily access the indoor environment (& therefore your pet) through open doors & windows.
Heartworms donât survive as well in cats as they do in dogs, but cats are still at risk for heartworm disease. However, diagnosing heartworms in cats is not as easy, & testing is not as simple, or accurate, as in dogs. In addition to blood work, testing in cats can include X-rays and ultrasounds.
Unlike for heartworm disease in dogs, there is no FDA-approved treatment for killing adult heartworms in cats. Because of the additional complications associated with diagnosing and treating cats, prevention becomes the best weapon against heartworms in cats. Itâs best to place both indoor & outdoor cats on a year-round, FDA-approved medication to prevent heartworms. For cats, there are both topical & oral prevention medications.
Testing for heartworms in ferrets is also not as easy, simple, or as reliable as in dogs. No drugs are FDA-approved to treat heartworm disease in ferrets, so prevention is critical. There is one drug (Advantage Multi for Cats) approved to prevent heartworms in ferrets. Itâs a topical medication, & is also useful for killing adult fleas.
Useful Tips About Heartworms & Your Pet
- Talk to your veterinarian about when and how often to test your pet for heartworms.
- Talk to your veterinarian about which type of heartworm prevention medication is best for your pet. For example, pet owners with children should pay particular attention when using topical treatments, which are applied to the skin, & follow the directions carefully to minimize the childâs exposure.
- Heartworm prevention medications are by prescription onlyâso beware of an internet site or store that will dispense medicine without a prescription.
- FDA monitors approved heartworm prevention medications for problems that may occur with use, such as unexpected side effects. Pet owners are encouraged to report any side effects to their veterinarian & the drug company that manufactured the prevention medication.
Updated: June 7, 2018