Heartworm (Dirofilaria immitis) is a large worm - the adult worm can be up to 14 inches long lives in the right side of the heart and pulmonary arteries of an infected dog. Dogs acquire heartworm infection through bites from infected mosquito with heartworm larva.
In the pulmonary arteries of an infected dog, the worm generates an inflammatory response. Presence of a lot of worms reduces the capacity of the heart and this heart must work extra hard to compensate the deficit.
Microfilariae (First Stage Larvae). female worms after mating with adult male in the infected heart they begin laying directly baby worms (larva) that called microfilariae. Microfilariae are released into the circulatory system waiting to be slurped up by a mosquito taking a blood meal and carried to a new host which is usually a domestic dog, coyote, or fox (although a wide variety of other animals can also be infected such as cats and ferrets, in rare instances humans). Microfilariae may live up to two years within the host dog, they die of old age after this period, if a mosquito has not picked them up. Microfilariae may also be transmitted across the placental barrier to puppies from infected mother.
Heartworm preventive Medication such as Ivermectin, selamectin, and milbemycin based will kill microfilariae (fisrt stage larvae), but they have little effect (L5, young adult heartworms) or no effect against Dirofilaria immitis (adult heartworms).
Inside the infected Mosquito:
The microfilariae will take few weeks to develop to L2s and finally to L3s, the stage capable of infecting a new dog usually through the dog nose which is vulnerable to mosquito bites.
Inside the infected Dog:
When a dog is bitten by an infected mosquito, the L3 is not deposited directly into the bloodstream will develop to L4 in 1-2 weeks that lives in the skin until develops to the L5 stage (young adult) that migrates to the heart and pulmonary arteries, where it will mate approximately five to seven months after first entering the infected host. This is why there is no point in testing puppies less than five months of age for adult heartworm antigen.
Heartworm disease Signs:
A mild persistent cough, decreased appetite, exercise intolerance, fatigue after moderate activity, and weight loss. If you notice one or more of these symptoms contact your veterinarian or call our veterinary clinic in Newmarket Aurora area at 905-898-1010 even your pet is dewormed. Deworming usually does not include medicine that can be effective against Heartworm. Read more on Heartworm in Dogs and Cats