The Hidden Dangers of Mosquitos for Your Beloved Pet

As the warm weather rolls in, so do the dreaded mosquitos. While they are notorious for spreading diseases like malaria and West Nile virus to humans, it’s important to remember that our furry friends are not exempt from their harm. Mosquitos can infect animals with diseases, including heartworm, posing a serious threat to their health and well-being.

Heartworm Disease: A Silent Threat

Heartworm disease is a grave condition that can lead to severe lung disease, heart failure, and damage to other vital organs. It primarily affects dogs, cats, and ferrets. When an infected mosquito bites an animal, it ingests microscopic heartworm larvae. As the mosquito moves on to its next victim, it deposits these larvae, continuing the vicious cycle.

It takes approximately 6 to 7 months for the larvae to mature into adult heartworms. Once they reach adulthood, the female heartworms release their offspring into the infected animal’s bloodstream. Adult heartworms resemble cooked spaghetti, with males reaching 4 to 6 inches in length and females growing up to 10 to 12 inches.

Heartworm Disease in Dogs


Symptoms of heartworm disease in dogs may vary depending on the number of worms present, also known as the “worm burden.” Dogs with a low worm burden, recent infections, or a less active lifestyle may not show obvious symptoms. However, those with a heavy worm burden, long-standing infections, or high activity levels are more likely to display noticeable signs.

Typical symptoms include a mild persistent cough, reluctance to exercise, fatigue after moderate activity, decreased appetite, and weight loss. The severity of the disease is influenced by the dog’s activity level and the stage of heartworm disease it has reached.

Stages of Heartworm Disease

  • Stage 1: No symptoms or occasional cough.
  • Stage 2: Mild to moderate symptoms, such as occasional cough and tiredness after moderate activity.
  • Stage 3: More severe symptoms, including a sickly appearance, persistent cough, tiredness after mild activity, trouble breathing, signs of heart failure, and changes visible in chest x-rays.
  • Stage 4: A life-threatening condition where a mass of heartworms obstructs blood flow, requiring immediate surgical removal. Even with surgery, survival rates are low. If left untreated, heartworm disease progresses, damaging the heart, lungs, liver, and kidneys, eventually leading to death.
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Treatment for heartworm disease is not easy on dogs. It involves a series of injections using an FDA-approved drug containing arsenic, along with other medications. This treatment can be toxic to the dog’s body, potentially causing complications such as life-threatening blood clots in the lungs. It is also costly, requiring multiple veterinary visits, blood tests, x-rays, hospitalization, months of exercise restriction, and diligent care.

The Power of Prevention

Prevention is the best weapon against heartworm disease. The FDA has approved various medications that effectively prevent heartworms in dogs. These medications, such as topical liquids applied to the skin or oral tablets taken monthly, require a veterinarian’s prescription. Some preventive treatments can also combat other parasites, such as roundworms, hookworms, fleas, ticks, and ear mites.

To ensure your dog’s safety, it’s crucial to have them tested for heartworms before starting any preventive medication. Heartworm preventives do not kill existing adult heartworms, and administering them to an infected dog can be harmful or even fatal due to a shock-like reaction from dying larvae.

Heartworm Disease in Cats: A Unique Challenge

Cats can also contract heartworm disease from mosquitoes, although they are less prone than dogs. The lifespan of heartworms in cats is shorter, averaging 2 to 4 years. Additionally, cats typically have a smaller number of heartworms, but even a few worms can heavily infect their small bodies.

It takes 7 to 8 months for heartworm larvae in cats to mature into adults and produce offspring. Unlike dogs, only 20 percent of cats with heartworm disease have larvae in their bloodstream. Symptoms in cats often manifest as difficulty or labored breathing, vomiting, decreased activity, loss of appetite, weight loss, convulsions, blindness, and fluid in the lungs. However, not all infected cats show signs of illness, and some may even rid themselves of heartworms without displaying symptoms.

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Detecting heartworm infections in cats is challenging. Veterinarians typically rely on a combination of blood tests, along with the cat’s symptoms and additional diagnostic procedures like x-rays and ultrasounds, to reach a conclusive diagnosis. Negative test results don’t rule out heartworm infection, and positive results may not always indicate an active infection.

Heartworm Disease in Ferrets: Vulnerable and Overlooked

Ferrets, like dogs and cats, can contract heartworm disease through mosquito bites. Despite being indoor pets, ferrets remain at risk. Although they are highly susceptible to heartworm infection, their symptoms more closely resemble those in cats.

Infected ferrets usually have low worm burdens, and blood tests to detect heartworm infections are unreliable. Symptoms of heartworm disease in ferrets include decreased activity, coughing, trouble breathing, overall weakness, and, in severe cases, heart failure.

Prevention and Treatment for Ferrets

Regrettably, no FDA-approved drugs are available for treating heartworm disease in ferrets. The only preventive medication approved for ferrets is Advantage Multi for Cats, a topical solution applied monthly. This product not only prevents heartworms but also treats flea infestations in ferrets by eliminating adult fleas. Year-round prevention medication is highly recommended for all ferrets, considering their susceptibility to heartworm disease.

The Importance of Prevention Cannot be Overstated

Remember, only a veterinarian can prescribe appropriate heartworm treatment and prevention for your beloved pets. Heartworm preventive medications do not eliminate adult worms, underscoring the critical role of prevention. It’s far easier and more cost-effective to prevent heartworm disease than to treat it afterward.

If you have any concerns or questions about heartworm disease or need to schedule your pet for a heartworm test or preventative medication, don’t hesitate to reach out to Katten TrimSalon. We care about the well-being of your furry companions as much as you do. Together, let’s protect them from the hidden dangers of mosquitos.

Sincerely, Dr. Tammy Stevenson
Katten TrimSalon, Cedar Falls, Iowa