Mosquitoes Pass Disease on to Dogs

Q: We have recently moved from Columbus, Ohio, and have heard a lot about heartworm disease in dogs. We are planning to get a Doberman from a breeder in the next two months. Do we need to have our puppy treated for heartworm?

L. Daniels, Huntington Beach

A: Heartworm disease in dogs is caused by a worm called Dirofilaria immitis and is spread most commonly by the bite of infective mosquitoes. Orange County is not endemic with heartworm disease, based on survey blood samples done by veterinarians in the area. However, with the constant influx of people and their pets from areas with heartworms, there is always the possibility that this disease could occur in Orange County.

The worm develops primarily in the right side of the heart. An adult fertile female produces larvae that enter the circulation system. A mosquito ingests blood from an infected dog. The larvae further mature in the mosquito and are deposited in the next dog that the mosquito bites. These larvae enter the circulation and develop into adults in the heart. Dogs who have heartworm disease develop a persistent cough, and exercise weakness. Some tend to lose weight because of loss of appetite.

For your puppy--find out if the breeder lives in a heartworm area and if the mother is negative for heartworms. Testing is usually done by six months of age. A blood sample is drawn and divided into two parts: one to test for circulating larvae (microfilaria) and the other to test for the antigen caused by an adult heartworm. These tests should be done before treating your dog with any medication. If heartworms are present, intravenous medication is given to kill the adult worms and circulating larvae.