What is Heartworm and How Can You Prevent It?

Heartworm disease is a severe and often undetected threat to dogs. Heartworms, unlike fleas and ticks, are not visible to your dog. When heartworm symptoms appear, it is often too late for the dog to recover completely. As a result, prevention is the only way to truly protect your dog from the dangers of heartworm disease. But what is heartworm and how can you prevent your dog from getting it?

Heartworm disease is a serious condition that causes severe lung disease, heart failure, organ damage, and death in pets, primarily dogs, cats, and ferrets. It is caused by a parasitic worm called Dirofilaria immitis, which is spread through mosquito bites.

The Life Cycle of Heartworms in Dogs

Adult female heartworms release their offspring, known as microfilariae, into the bloodstream of an infected dog. When a mosquito bites an infected dog, the mosquito contracts microfilariae. While living inside the mosquito for 10 to 14 days, the microfilariae develop into infective larvae under the right environmental conditions.

Microfilariae must pass through a mosquito to become infective larvae. When an infected mosquito bites another dog, the infective larvae are transmitted to the dog via the bite wound. It takes 6 to 7 months for infective larvae to mature into adult heartworms in a newly infected dog. Adult heartworms mate and the females release their offspring into the dog’s bloodstream, completing the life cycle. See a diagram of the heartworm life cycle in dogs.

Heartworm disease is not contagious, meaning a dog cannot catch it from another infected dog. The bite of a mosquito only transmits heartworm disease.

Heartworm has a lifespan of 5 to 7 years inside a dog. Adult heartworms resemble strands of cooked spaghetti, with males reaching lengths of 4 to 6 inches and females reaching lengths of 10 to 12 inches. The worm burden is the number of worms living inside an infected dog. The average worm burden in dogs is 15, but that number can range from 1 to 250.

What is the Treatment for Heartworm?

Melarsomine dihydrochloride, trade names Immiticide and Diroban, is an arsenic-containing drug approved by the FDA to kill adult heartworms in dogs. It is administered via deep injection into the back muscles of dogs with stabilized class 1, 2, or 3 heartworm disease. Advantage Multi for Dogs, imidacloprid and moxidectin, are FDA-approved drugs for removing microfilariae from the dog’s bloodstream. Advantage Multi for Dogs is a topical solution that is applied to the skin of the dog.

Heartworm disease treatment is not easy on the dog or the owner’s wallet. Treatment may be toxic to the dog’s body and result in serious complications, such as life-threatening blood clots in the dog’s lungs. Treatment is costly because it necessitates multiple veterinarian visits, blood tests, x-rays, hospitalization, and injections.

Prevention is the Key 

Many products are FDA-approved for heartworm prevention in dogs. All require a prescription from a veterinarian. Most products are administered monthly, either as a topical liquid applied to the skin or as an oral tablet. There are chewable and non-chewable oral tablets available. Every 6 or 12 months, a single product is injected under the skin, and only a veterinarian can administer the injection. Other ingredients in some heartworm preventives are effective against certain intestinal worms, such as roundworms and hookworms and other parasites such as fleas, ticks, and ear mites.

Preventive medication should be done all year Consult your dog’s veterinarian to determine which preventive is best for him.