Dog Articles - Mosquitoes Pose Major Health Risks to Your Dog

Mosquitoes Pose Major Health Risks to Your Dog

I’ve spent the last month in the North Carolina countryside. It was hot and humid and the house was right on the water with a great big marsh. I couldn’t believe how many mosquitoes there were in that part of the state; I felt like they were swarming me all the time!

Mosquitoes aren’t just a biting, buzzing annoyance; they are carriers of a dangerous parasite that has claimed the life of many an unwary dog lover’s pet. Mosquitoes play host to the larval stage of the heartworm--a parasite that can, when transmitted by mosquito via bite, infest your dog. This can lead to intensive, costly treatment or even death.

What is a Heartworm?

Heartworms are parasites (organisms that grow, feed, and find shelter on or in another living being without being of benefit to the host entity) which infect dogs. The early larval stage of this parasite lives in the blood of infected dogs. When a mosquito bites an infected dog, parasites travel into the mosquito and develop for around three weeks. After that period of time, the heartworms are ready to leave the mosquito. They move to the mouthparts of the insect and wait for it to bite a dog. They then travel into the bloodstream and spend the next several months developing in the dog’s tissue before they mature and move to the animal’s heart. They then multiply, their larva circulating in the dog’s bloodstream, waiting to hitch a ride in a mosquito and continue the cycle of infection.

Adult heartworms can grow to 13 inches long. They grow and multiply in the right side of the heart, and in arteries in the lungs; they also lodge in veins entering the heart and veins of the liver. They block the blood supply to vital organs, causing organ failure and eventually death.

Heartworms are found in all 50 US states. They are most prevalent on the Atlantic and Gulf coasts, along river tributaries, and in the south-central and south east parts of the US. As heartworms are spread by mosquitoes, areas with heavy mosquito populations have the highest incidence of heartworms.

Heartworms can be detected with a blood test and adult heartworms can be seen in the heart and lungs in X-rays.


One important fact to remember is that there is a period of six to seven months between infection and the worms’ maturing and moving to the dog’s heart; symptoms may not manifest for up to a year after infection. Having your dog tested for heartworms is the best way to catch the disease before it progresses into a dangerous condition.

The following are symptoms which are exhibited in dogs with heartworm disease: a cough that increases with exercise, syncope (fainting/losing consciousness), tiring easily, weakness and listlessness, weight loss, coughing up blood, breathing difficulties, and finally, liver failure or congestive heart failure.


If you find that your dog has heartworms early enough for him to be treated, it is still a costly and dangerous undertaking. Your best bet as a dog owner is prevention.

There are many heartworm preventative medications available for dogs. Some treat and prevent intestinal parasites as well, and some even protect against fleas and ticks too. Before you put your dog on a heartworm preventative, however, it is important that you have your dog tested for heartworms. Giving your dog a heartworm preventative when he is already infected (even if he isn’t showing symptoms) can be deadly.

One way to help prevent heartworms in not only your dog, but your community as well, is doing your part to control the mosquito population. Mosquitoes lay their eggs, and their larva develops in shallow standing water. Disposing of or dumping-out anything holding standing water makes a huge difference in your local mosquito population. This includes wheelbarrows, tires, hubcaps, pool covers, trash cans, recycle bins, children’s toys, and sheets of plastic. Store anything that might hold rainwater upside down. If your children have a tire swing, drill drainage holes in it. Keep your bird bath mosquito-free by changing the water a few times a week and keeping it clean.

Ornamental ponds are breeding grounds for mosquitoes, but don’t worry, you don’t have to drain your pond to keep your dog safe. There are tablets available at pond and garden stores that nix mosquito larvae but are safe for other aquatic life. You can also stock your pond with varieties of fish that feed on mosquito larvae.

Another easy way to keep mosquitoes away from your dog is to keep him inside during peak mosquito times—dawn and dusk.

I hope everyone has a fantastic weekend and if you’re in a climate like mine, I hope the buzzing buggers don’t carry you away!

Stay tuned for Monday’s tips on dog-rule ideas for kids.

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