Ask the Entomologist Preventing Ticks

Ask the Entomologist: Heartworm

April is Heartworm Awareness Month. Did you know that mosquitoes are the sole cause of heartworm? Preventing your pet’s exposure to mosquitoes can be helpful, but pet owners know that regular treatment for heartworm is vital to maintaining your dog’s or cat’s health.

Dr. Stoops answers a few questions about heartworm causes and effects, that help give us all a better understanding about why preventative treatment is so important. Please visit the American Heartworm Society (AHS) website to for more information on this and other heartworm related topics.

Is heartworm really an actual worm?

Yes. Heartworms are a type of filarial or roundworm that are parasites of animals.

My cat doesn’t go outside at all, and my dog is really only outside to “do his business” and take walks. Why would I need heartworm preventative for either of them?

In this case, prevention is worth a pound of cure. According to the AHS, your indoor cat may spend more time exposed to mosquitoes on a balcony, or near an open window than you realize. Even dogs that only spend brief amounts of time outside can be exposed in the morning and evening when most mosquitoes are biting.

Regardless, there is no heartworm treatment for felines. Though rare, if your cat gets a serious worm infection, it could lead to a bad outcome that could have been prevented. For canines, the treatment is costly, lengthy, and difficult on the dog. Preventing the infection in the first place is easier than trying to cure your dog of heartworm.

I sometimes skip a month or two of treatment, especially when it’s colder out and I know there aren’t mosquitoes in my yard. That’s fine, right?

According to the AHS, skipping even one month of treatment is not recommended. The worms are only susceptible to the worm-killing agent in the preventive treatment before they reach the late immature stages or the adult stage. Once the worms reach these later stages of development, the preventive is less effective and most likely won’t rid the dog of the worm infection. By skipping even one month, you may miss stopping the development of the worms to a stage where more complicated treatment is necessary.

Isn’t heartworm curable if my pet does contract it?

It is, but prevention is much better. According to the AHS, the treatment is “expensive and complex”. The treatment involves a series of injections and regular testing. The animal must limit physical activity to lower the damage done by the worms to the heart and lungs. I highly recommend going to the FAQ section of the AHS website for more details on the treatment and details between the treatment of dogs and cats.

Dr. Craig Stoops LCDR MSC USN (ret.) is a retired U.S. Navy Medical Entomologist who has conducted mosquito control and research in the United States and around the world. Craig wields a B.S. in Biology from Shippensburg University, and both an M.S. and a Ph.D. in Entomology from Clemson University. He is Board Certified by the Entomological Society of America in Medical and Veterinary Entomology.


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