Pet Points: Summer, mosquitoes bring increased heartworm risk

After a long work day, I love sitting in the backyard listing to music and watching the dogs play. Last week as soon as I sat down, I felt the bite. Mosquitoes found me and starting feeding on my arm.

Mosquitoes transmit serious diseases, including heartworm in dogs and cats. Pet owners need to remember that preventive measures are much better than treating this disease. It is estimated that 250,000 dogs are diagnosed yearly with heartworm, and the number is increasing. In all 50 states, current recommendations for dogs are for 12 months of preventive medication. Even with monthly medications, experts insist on annual testing. The common blood tests also include detection for tick-borne illnesses like Lyme disease.

Cats are also at risk for heartworm infections. Outdoor cats should be on prevention and even an indoor cat has some risk. The disease is different in cats and a very small number of worms can cause a condition called Heartworm Associated Respiratory Disease. A single worm can cause vomiting and breathing difficulty in cats. In contrast, dogs may have 200 worms blocking heart vessels.

Veterinarians prescribe a number of products to prevent heartworm disease. Most dogs take monthly chewable tablets, but topical and injectable medications are also effective. Cats can receive topical or oral medications. No matter what monthly product is used, it must be given on a regular schedule. Some clients type the medication due date into their computer or phone. Others pick a specific date each month; stickers to place on a calendar are included in the package. I write the dates medication is administered on the back of the box.

Heartworm medication may also work against roundworm and hookworm. These internal parasites can transmit disease to people. We advise pet owners to pick up after their dogs and make sure children wear shoes outside and wash their hands after playing outdoors, especially before eating. During the winter, the monthly medications continue to control these internal parasites.

Treatment for heartworm disease is complex and expensive. Radiographs, blood tests and EKGs are necessary. Dogs often get a series of painful injections and the pets must be kept very quiet as the worms die and disintegrate inside them. Untreated and undiagnosed heartworm infections can be fatal or debilitating. Even with treatment, some pets die.

Heartworm is epidemic in the South. As pets travel or are transported for adoption, the disease continues to expand its range, putting all dogs and cats at increased risk. And warm and wet weather means higher mosquito populations. The forecast this summer is for a continued increase in heartworm disease in the Northeast.

Lawrence Gerson is a veterinarian and founder of the Point Breeze Veterinary Clinic. His biweekly column is intended to educate pet owners. Consultation with a veterinarian is necessary to diagnose and treat individual pets. If you have a question you’d like addressed in Pet Points, email Please include your name and municipality or neighborhood.