How Often Should Heartworm Pills Be Given to Dogs?

Heartworm can be fatal to dogs, but the good news is that you can both prevent and treat this disease in dogs. Dog heartworm treatment is possible if a dog becomes infected, but it is difficult and expensive to treat. For that reason, heartworm prevention is recommended. When it comes to heartworm medication, how often you give it to your dog is important.

Heartworm disease is a serious infection from a parasitic worm called Dirofilaria immitis. The U.S. Food & Drug Administration says it results in severe lung disease, heart failure, other organ damage, and death in pets, mainly dogs, cats, and ferrets. The worm's primary host is the dog, which means the worms live out their life cycle within dogs; they are less successful in cats or ferrets. The parasite is transmitted by mosquitoes. The worms live in the heart, lungs, and blood vessels of the infected animal.

It takes six or seven months for the worm's offspring to mature into adult worms. The adult heartworms mate within the dog and produce offspring. Heartworm disease is not contagious, meaning that a dog cannot catch the disease from being near an infected dog. Heartworm disease is only spread through the bite of a mosquito. Female adult heartworms look like strands of cooked spaghetti and are 10 to 12 inches in length, with males about half that size.

The best dog heartworm treatment is prevention. Medication is typically given in the form of pills, but it can also be a topical liquid applied on the skin or a chewable or nonchewable oral tablet. When it comes to heartworm medication, how often it is given depends on the medication. Most are given once a month, but an injection given by a veterinarian can be given every six months or once a year.

The U.S. Food & Drug Administration says dog heartworm medication should be given year-round because there are mosquitoes year-round. There are significantly fewer mosquitoes in the winter in most areas, but there is still a risk of being bitten by an infected mosquito.

Heartworm prevention medication is a pill given once a month. Once-monthly medication is called Heartgard. Heartgard says that this monthly medication keeps dogs safe because the pills kill heartworms in the larval stage and help prevent them from developing into adults.

If you stop heartworm prevention medication and your dog is bitten by an infected mosquito, then the larva will begin to grow. Resuming heartworm prevention medication after the larvae have already started to grow can cause serious problems for your pet. The U.S. Food & Drug Administration says resuming the medication can kill so many offspring that it can cause a fatal shock to your dog's system. Also, importantly, the prevention medication will not kill adult heartworms, which will continue to reproduce.

The American Heartworm Society says all dogs should be tested annually for heartworm infection to be sure that an infection hasn't taken hold during a gap in preventive treatment. Heartworm prevention for puppies can begin at 7 months of age or younger regardless of whether they have had a test. This is because it takes at least six months for a dog to test positive after he has been infected.

Heartworm medications are highly effective, but dogs and puppies can still become infected. Heartgard says Heartgard can be given to a puppy as young as 6 weeks old in the form of a beef chew given every month.

The U.S. Food & Drug Administration says heartworm in humans is rare. It is possible for a human to be bitten by a parasite-infected mosquito, but humans are not a heartworm's preferred or natural host. In humans, heartworms usually cannot become established. The larvae usually migrate to the arteries of the heart and lungs and die before they become adult worms.