Stages of Canine Heartworm

Heartworms are a major pest of dogs, especially in rural areas where there are high populations of mosquitoes. Severe infestation of worms in the heart can cause shortness of breath, coughing, muscle weakness and heart failure. Heartworm can be fatal if not treated or prevented with veterinary medicine. Protecting dogs, especially those that sleep outside, from mosquitoes will help to keep them heartworm free

  1. Mosquito Bite

    • When a mosquito bites an already heartworm infected dog it will take up immature heartworms. These will remain inside the mosquito for roughly two weeks, until they are ready to infect a dog themselves. The worms will then travel to the mouth-parts of the mosquito and wait until the mosquito lands on its next victim. When the mosquito bites, the immature heartworms are transferred to the new host.

    Growth in Body Tissues

    • Once inside the dog the immature heartworms leave the blood stream and burrow into the flesh of the dog. Here they will grow for up to three months. Any heartworms deposited in an animal other than a dog are likely to die within a week. After growing, the heartworms go back into the bloodstream and head for the right side of the heart and pulmonary arteries.

    Sexual Maturity

    • Once inside the heart the worms grow to sexual maturity. Male and female worms mate and the female releases young worms into the bloodstream. These immature worms then travel around the body of the host waiting to be ingested by another mosquito. The adult heartworms will remain alive and producing young in the heart of the dog for roughly six years.