Heartworm

A species of parasitic worm that lives and reproduces in the chambers of the heart of an animal. Microscopic, immature worms (microfilariae) circulate in the blood and are taken in by mosquitoes that bite the animal. Microfilariae mature in the mouthparts of the mosquito and infect another susceptible animal bitten by the same mosquito. A rare, but potentially life-threatening parasite, that travels through a cat's bloodstream and grows large in the heart.