How To Reduce Your Dog’s Risk Of Heartworm

You’re outside playing fetch with your favorite canine fetcher and you hear a familiar and unwelcome buzzing in your ear. Mosquitoes. They can quickly ruin a pleasant evening and cut fetch time short with all that swatting and slapping.

Most people are probably aware that certain types of these pesky insects can transmit diseases to people (like Zika virus, West Nile virus and dengue). Mosquitoes are also the transmitters of heartworm in dogs, which is a potentially deadly disease. The good news is that there are very effective preventives available for reducing the risk of a heartworm infection in your dog.

Mosquitoes and Heartworm Go Hand in Stinger

First, a scary fact: one bite from an infected female mosquito is all that’s needed to cause heartworm in dogs. Eeek! Another fact that is a little more reassuring for pet owners is that heartworm is only transmitted by mosquitoes; it is not spread from dog to dog, dog to cat or from dogs to people. So if your dog does become infected, they can’t spread heartworm to other members of your family (fur family included).

Let’s learn more from the American Heartworm Society about these vicious vectors and how they transmit heartworm to dogs. The mission of the American Heartworm Society is to lead the veterinary profession and the public in the understanding of heartworm disease.

Dogs are the natural hosts of heartworm; the heartworms mature into adults, reproduce and have offspring while living inside the dog. Heartworms live in, and can cause long-lasting damage to, the heart, lungs and pulmonary arteries. Mosquitos are an essential part of the heartworm life cycle as this is where the baby worms (larvae) develop and mature into their infective stage. The life cycle of heartworm in dogs and mosquitoes is outlined below.

Mosquitoes Are Everywhere

When you think about mosquitoes, you probably think of hot, humid climates with plenty of water. While these are certainly areas where mosquitos are common, it’s also possible for mosquitoes to live in drier and colder areas of the country. This means that for most people, no matter where you live, it’s possible for your dog to become infected with heartworm. Wildlife like coyotes, wolves and foxes can be carriers of heartworm and also introduce heartworm into your area.

A 2019 survey by the American Heartworm Society showed that even though the most prevalent number of cases reported per clinic was in the southeastern United States, heartworm infections were diagnosed in all 50 states. The survey is conducted every three years to understand the impact of heartworm across the nation and in specific regions.

Mosquitoes can also live year-round in many parts of the country. Just a few days above 57 °F will allow heartworm larvae to develop into the infective stage within the mosquito, ready to be transferred to a dog in a single bite. Winter doesn’t mean bye-bye mosquitoes — they could be hiding inside your nice warm house ready to bite.

Make Your Home Less Inviting for Mosquitoes

You can help reduce the risk of your dog being bitten by a mosquito by keeping them inside when mosquitoes are most active (dusk and dawn). It’s also a good idea to make sure there are no items in your yard that have standing water in them as these are perfect places for mosquitoes to lay eggs.

The American Heartworm Society explains that some mosquitoes do breed and hatch in response to rainfall but others prefer objects like old tin cans, tires and even bird baths. In urban areas, mosquitoes will even breed in watered lawns, garden features and underground storm systems. Keeping standing water out of your yard will help prevent you from unintentionally creating a mosquito breeding ground.

While removing standing water can help reduce mosquito activity around your home, the chance of you protecting your dog from being bitten by a mosquito their whole life is virtually zero. This is why year-round medication that prevents heartworm infection is so important for your dog — particularly when just one bite from an infected mosquito is all it takes for your dog to become infected.

Heartworm Prevention Is Key!

Heartworm prevention is easy, effective and a lot less expensive than treating your dog for heartworm disease. Trying to treat your dog after heartworm infection has occurred is risky to their health, particularly if the infection is advanced. Year-round heartworm prevention medication is the most effective step you can take to reduce the risk to your dog’s health.

Preventive heartworm medications are available as monthly oral tablets or chews and monthly topical skin applications. There is also an injection that is administered every 6 or 12 months. The American Heartworm Society has a list of heartworm preventives currently approved by the U.S. Food and Drug Administration (FDA). All of these medications are only available by prescription from your veterinarian. Some of the heartworm medications also include preventives for fleas, ticks, intestinal parasites or mites.

Testing for Heartworm in Dogs

Because there are few (if any) signs of early heartworm infection, the American Heartworm Society recommends the following heartworm testing protocols. Puppies under 7 months can start heartworm preventives at any time without a test but should be tested in 6 months, tested again 6 months later and then yearly. Dogs 7 months or older who have never been administered a preventative, or have missed or been late on a preventive dose, should be tested for heartworm before they start (or re-start) their medication and be tested again 6 months later and then yearly.

An article by the FDA explains that it’s very important to know if dogs have a heartworm infection before starting preventive medication. Preventives won’t kill adult heartworm, and if the dog is infected with the adult worms, it’s possible for microfilariae to be in the bloodstream. The preventives could kill the microfilariae, which could trigger a shock-like reaction in the dog that could be fatal.

The FDA article describes two types of heartworm tests available for dogs that are performed using a blood sample. The antigen test looks for proteins (antigens) in the dog’s bloodstream that were released by adult female heartworms. The earliest the antigens can be detected is around five months after the dog was bitten by the infected mosquito. The other test detects microfilariae in the blood, which indicates that the dog is infected with adult heartworms. This is because only adults can reproduce and release microfilariae.

Heartworm in dogs is a scary disease but also very preventable with annual testing and year-round preventive medication. And it’s a good idea to try to keep those pesky ’skeeters away from your dog, too!

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