Heartworm Prevention

Heartworm disease is caused by parasitic worms (Dirofilaria immitis) that live in the heart, lungs, and blood vessels of infected pets. Adult worms can grow up to 12 inches long. The disease causes lasting damage to these organs and can be fatal if untreated.

Heartworm is transmitted exclusively through mosquito bites. An infected mosquito deposits microscopic heartworm larvae into your pet's skin. The larvae migrate through the body over about 6 months, eventually reaching the heart and lungs where they mature into adults.

Yes. While heartworm is more common in dogs, cats are also susceptible. Even indoor cats are at risk—mosquitoes get inside. In cats, even a small number of worms can cause serious lung disease (HARD — heartworm-associated respiratory disease). There is no approved treatment for cats, making prevention essential.

Florida's warm, humid climate supports mosquito populations all 12 months of the year. Unlike northern states where freezing temperatures kill mosquitoes seasonally, St. Petersburg never has a true mosquito-free period. Missing even one month of prevention creates a window for infection.

We offer several options: monthly chewable tablets (like Heartgard or Interceptor), topical treatments, and combination products that prevent heartworm plus fleas and ticks. We'll recommend the best option based on your pet's size, species, and lifestyle.

We recommend annual heartworm testing for all dogs, even those on prevention. No preventive is 100% effective—a missed dose, vomited pill, or product failure can leave gaps. Testing ensures early detection if prevention lapses. Cats should be tested before starting prevention.

If your dog tests positive, we perform staging diagnostics (chest X-rays, bloodwork) to assess severity. Treatment typically involves a series of injections to kill adult worms, strict exercise restriction for several months, and follow-up testing. Early detection makes treatment safer and more effective.

Heartworm treatment for dogs typically costs $1,000-$3,000+ depending on the severity of infection and the dog's size. This includes diagnostics, multiple injection visits, hospitalization, and months of follow-up. By comparison, a year of prevention costs roughly $100-$200.

Not in Florida. The American Heartworm Society recommends year-round prevention in all 50 states, and this is especially critical in Florida where mosquitoes remain active in every month. Gaps in prevention are the number one cause of heartworm infections.

Early stages often show no symptoms. As the disease progresses, dogs may develop a persistent cough, exercise intolerance, decreased appetite, and weight loss. Advanced cases can cause heart failure, a swollen belly from fluid accumulation, and sudden collapse.

Restart prevention immediately and schedule a heartworm test in 6 months (it takes that long for new infections to be detectable). Do not double up on doses. The sooner you restart, the better—every month without prevention is another month of exposure risk.

Yes! Most heartworm preventives can be started as early as 6-8 weeks of age. Starting early is especially important in Florida, where mosquito exposure begins immediately. We include heartworm prevention in our puppy wellness program.