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Heartworm prevention & treatment


Prevention principles

Prevention medications target larvae and kill them before they have a chance to establish an infection. Did you know that buying heartworm prevention every month for a dog’s entire life is often CHEAPER than paying for ONE heartworm treatment? Treatment for heartworm disease requires many components and may end up costing the owner more than they would have paid if they used preventive medication.


  • For dogs, CAH offers Sentinel products that prevent heartworms, intestinal parasites, and fleas. This medication comes in a tasty chewable tablet form that is given once monthly.

  • For cats, CAH offers Bravecto Plus topical medication that provides protection against heartworms, intestinal parasites, fleas, and ticks for two months. That means you don’t have to worry about getting your cat to eat a pill, AND it only needs to be applied every other month! Remember – there is NO reliable treatment for heartworm disease in cats, prevention is often the ONLY method of protection!


Giving heartworm prevention year-round is the best way to prevent heartworm infection. Administering the prevention on-time each month is especially important during the summer months when mosquitoes are most active. But we can never be too sure when we’ll see the first mosquito in spring or the last mosquito in fall, which is one reason the American Heartworm Society recommends year-round prevention. Our homes can also create great microhabitats for bug populations to survive through the winter.


We recommend testing dogs for heartworm disease before administering

certain heartworm prevention products because if the pet is already

infected, the circulating worm larvae may die faster than the body can

dispose of them, which can lead to anaphylaxis.



Treatment principles

Treatment in dogs is slow and stepwise in order to prevent large numbers of worms from dying all at once, which can block blood flow in the lungs (pulmonary thromboembolism) and risks sudden death.


  • Specific heartworm prevention medications are used to prevent the growth of new larvae without risking anaphylaxis. Occasionally, treatment may consist only of a heartworm preventative medication, which is called the “slow kill” method. At high doses administered over long periods of time, these medications can also be effective against adult heartworms. But this method is not typically preferred because the worms live longer, allowing the worms to cause more damage to the body than they would if we also utilized drugs to specifically target the adults.

  • Antibiotics are used to dampen the symbiotic relationship that the heartworms have with Wolbachia spp., making the worms more susceptible to targeted treatments.

  • Melarsomine is a drug that kills adult worms and is administered as a series of intramuscular injections.

  • Rest is key in the treatment of heartworm disease because it prevents excess blood flow that can lead to movement of worms, which can result in a thromboembolism from the worms becoming lodged in a vessel and blocking blood flow.


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