Keeping your pet parasite-free is an important part of their overall wellness, and heartworms are no exception to this rule. These parasites are extremely damaging and can threaten your pet’s life, but year-round prevention can help keep them safe. The All Creatures Animal Hospital team wants pet owners to understand the importance of year-round prevention, and how lapses in prevention can lead to heartworm disease.

How do pets get heartworm disease?

Heartworms are transmitted by mosquitoes, which pick up the tiny larvae from another infected animal’s blood. These infected animals (i.e., reservoirs) include other pets or wild mammals such as wolves, coyotes, foxes, and sea lions. While heartworms are not directly contagious from pet to pet, living near an infected reservoir increases your pet’s risk, because some of those mosquitoes could be carrying the disease.

Once inside your pet’s body, the heartworm larvae traverse through tissue until they reach the heart and large blood vessels nearby, where they mature into approximately foot-long adult worms that can reproduce and, left unchecked, could eventually number in the hundreds. In cats, only a few worms survive to adulthood and they usually cannot reproduce.

Heartworm signs and symptoms in pets

Heartworm-positive pets often look and act normal for several months or years after the initial infection, but eventually the worms cause local damage that can result in respiratory disease, heart dysfunction, or heart failure. Heartworm disease in dogs may cause:

  • Coughing
  • Exercise intolerance
  • Weight loss
  • Heart failure
  • Death

Cats may not show any signs, but heart dysfunction and sudden death are possible. Others develop respiratory or other systemic signs, including:

  • Coughing, wheezing, or difficulty breathing
  • Weight loss
  • Vomiting
  • Seizures
  • Death

Close-up of a cluster of long, pale roundworms with smooth, coiled bodies on a reflective surface. A veterinarian would note the prominent one in the foreground, showcasing a reddish section along its length.

Pet heartworm testing guidelines

The longer a pet has heartworm disease, the worse their prognosis. Early detection is vital for dogs, and we recommend annual testing that requires only a small blood sample and can be performed along with your pet’s other wellness services. Newly adopted dogs may require multiple tests several months apart to ensure they are infection-free. Routinely testing cats is not commonplace, but should be performed before starting a preventive medication, or in any cat suspected of heartworm infection.

Keeping pets safe with heartworm prevention

Heartworm infection, and subsequent heartworm disease, can negatively impact your pet’s health, or worse, can be fatal. Happily, we can prevent heartworm infections with a simple, monthly medication commonly known as heartworm prevention. Multiple topical or oral formulations that also control other parasites, such as roundworms and hookworms, are available.

Each heartworm preventive dose works retroactively, killing immature larvae that were transmitted in the prior weeks. Because you cannot predict mosquito activity, and because of the way preventives work, skipping months intentionally or accidentally missing a few months can allow larvae to mature into adults and lead to heartworm infection. Once larvae reach a certain stage, they can no longer be controlled with preventives.

Treatment for heartworm-positive pets

Heartworm treatment is possible for dogs, but no safe option is available for infected cats, who can only be monitored closely and provided with supportive care to counteract any respiratory or heart issues. Prevention is crucial for cats, including those who live indoors, because mosquitoes can easily come into your home.

Treatment for dogs is multi-faceted, takes several months, and can be costly. Prevention is the best option for your dog’s safety, because treating heartworm infection cannot reverse the existing damage. Infected pets are at risk for future heart problems, and treatment can be risky for debilitated pets or those with a high worm burden. Treatment can involve:

  • Hospitalization for injections to kill heartworm adults
  • Heartworm prevention to kill larvae
  • Pre-treatment antibiotics to kill heartworm-associated bacteria
  • Steroids to reduce allergic or anaphylactic reactions to toxins released by dying worms
  • Surgery, in severe cases

Don’t let mosquitoes or heartworms ruin your summer fun! Remove standing water from your property and keep your lawn cut short to reduce mosquito activity. Provide all pets with a year-round heartworm preventive, which can be combined with a topical flea and tick repellent product.

Ask our All Creatures Animal Hospital team to recommend the product combination that will work best for your pet’s lifestyle and personality, and that your budget can easily handle. Contact us to learn more about heartworm disease, or to schedule your pet’s next wellness visit and heartworm test. You can also visit the American Heartworm Society website to learn more.