Microfilariae are the small microscopic worms that live in the animal's bloodstream. They are released by the adult worms after mating occurs. Microfilariae can survive in the bloodstream of infected dogs for up to two years. These small worms are carried by mosquitos and are the source of infection for other dogs.

Drop of Blood Magnified Showing Microfilaria

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The removal of microfilariae is generally done prior to the removal of the adults. The American Heartworm Society recommends 1 to 3 months of a preventive medication prior to treating the adult worms. Your veterinarian will recommend the best medication for eliminating the heartworm microfilariae from your pet.

After heartworm treatment is performed, a heartworm prevention program should be established. Heartworm preventative medication is the key to preventing heartworm infection in pets.