The larvae must spend time inside a mosquito and then be transferred back into a dog or other susceptible animal in order to reach adulthood. In these animals, the adult heartworms are found in the heart, but their offspring will not be found in the bloodstream. These pets cannot spread the disease to mosquitoes, but can die from the presence of adult worms in the heart. Dogs may show no signs of infection if there are few worms in the heart. Signs may include exercise intolerance, nighttime cough, a belly distended with fluid due to right-sided heart failure, jaundice due to liver failure, or sudden death.
Prevention is crucial.
Due to the one month lag time and the warm stretches of weather in Maryland s winters, preventative should be continued year round. Many monthly preventative brands also control intestinal parasites. Daily preventatives have fallen in popularity. Skipped days risk infection. The medications will not affect the adult worms.