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.
Testing requires a blood sample.
It takes 5-6 months after the bite of an infected mosquito for heartworm disease to be detected. Puppies under six months of age are started on prevention without a test. Dogs that have missed a tablet are restarted on monthly preventative but should be tested in six months. Once testing has confirmed heartworm infection, treatment options are discussed. Immiticide is the newer form of treatment.