Feline Heartworm Treatment with Thiacetarcamide

Feline heartworm infections are less common than heartworm infestations in dogs, but can prove to be just as dangerous. It has recently become evident that the rate of feline heartworm infections is much higher than previously thought. In fact, some heavily affected geographical regions have a higher incidence of heartworm infections even than infections caused by the feline leukemia virus or the feline immunodeficiency virus.

Why Feline Heartworm Infections Are so Dangerous

The heartworm is evolved to infect dogs, and not cats. When a heartworm larva is in a dog's circulatory system, it can use chemicals in the bloodstream to navigate itself into the pulmonary arteries. Since the larva can only read chemicals in dog blood, they frequently get lost inside a cat's body, and are unlikely to survive.

Cats have a stronger immune system than dogs, which kills many worm larvae immediately after they enter the blood stream. Whereas a dog heartworm infection can consist of twenty five to fifty adult worms, it is uncommon for an infected cat to be home to more than six worms. Dogs have wider blood vessels than cats, so even though they are not as effective as fighting off the worms as cats, they are at less risk because a bigger infection is needed to clog up their circulatory system.

Cats, with smaller circulatory passages than dogs, are at a much higher risk. Not only are adult heartworms large enough stop the blood flow in a cat's pulmonary artery, but also lost or dead larvae can get caught in small blood vessels, possibly resulting in a blockage. Heartworms do not necessarily have to physically clog the blood vessel, because they can cause an inflammatory reaction in cats, which further narrows the already obstructed circulatory passageway.

Treatment with Thiacetarsamide

Thiacetarsamide is an injectable liquid that can be used to treat a feline heartworm infestation. It contains arsenic, which is effective at killing all adult heartworms. It was originally invented as a heartworm treatment for dogs, but it is also effective in cats, although it has not yet FDA approved for cats. It should be noted that thiacetarsamide is ineffective at killing the larval heartworms, and a separate medication, called a microfilaracide, is needed to remove heartworm larvae. Thiacetarsamide can either be a daily or weekly treatment, and cats living in heavily affected areas are recommended to stay on the medication year round.

Side Effects

The most common side effect of thiacetarsamide use in cats is vomiting. Some very rare, but also very serious, negative side effects are kidney or liver damage, or the circulatory condition known as thrombocytopenia (a deficiency of platelets in the blood, or the chemicals responsible for blood clotting). In very severe cases, a bad reaction to the dead worms inside the cat's body can cause death.

Heartworms can be an extremely uncomfortable and hazardous parasite for cats. If you live with your cat in an area where heartworm infections are common, it is important to regularly de-worm your pet, even if you have no evidence to suggest that the animal is infected. Better to be safe than sorry.