Heartworm Prevention

Heartworm (Dirofilaria Immitis) is a parasite that mainly infects dogs, but can also infect cats, ferrets, wolves, coyotes and in rare cases humans. These worms live in the cardiovascular system, specifically in the arteries that lead from the heart to the lungs. They compromise the flow of blood through the body simply by slowly clogging the arteries.


The life cycle of the heartworm has multiple stages. It starts with adult heartworms living in a host dog’s blood stream. These adults are constantly reproducing and creating what are called microfilaria, or larva stage 1 (L1).  When a mosquito bites the infected host and ingests a blood meal, it also ingests the L1. The L1 will mature into larva stage 3 (L3) inside the mosquito. Once the mosquito takes another blood meal from a dog that is not infected, it transfers the L3 to the dog, where it develops into the larva stage 4 (L4) and eventually into adult heartworms.


There are a couple of treatment options available for dogs that are diagnosed with heartworm. The preferred method of treatment is to use anti-parasitics to slowly kill off the worms at a rate that will not cause serious cardiovascular side effects. For this reason it usually takes months of deworming at very specific doses and involves some risk. The secondary method is surgical removal of the worms. This option is more expensive, but obviously does not take as much time and medication.


The best way to make sure your dog never suffers from heartworm is prevention, which can be done with a number of different anti-parasitics. Make sure to ask you stop by Dartmouth Veterinary Hospital about this if you live in an area that is effected by heartworm.

Written by Dartmouth Veterinary Hospital


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