Why Summer is Prime Heartworm Prevention Time for Pups

. 2 min read

It's the dog days of summer—and that means the mosquitos are out in full force (and ready to chow down on you and your pup.) While these pesky pests are usually a harmless annoyance for us, they can pose a real danger to your dog. The reason: Mosquitoes carry parasites that can cause heartworm, a serious and potentially fatal disease for pets.


The good news is, it’s totally preventable—and curable—if caught in time. You just have to know how to prevent it and which signs to look out for so you can get those sneaky worms out of your pet stat, says Jeff Werber, a licensed veterinarian and owner of the Century Veterinary Group in Los Angeles. “It’s a parasite, but it’s so easy to prevent,” he says. We answer all your heartworm questions to keep your pup safe:


What is heartworm?

Heartworm is a parasite called dirofilaria immitis that sets up shop in the major vessels of your dog’s heart and lungs. As the heartworms multiple, they can block those major vessels from going in and out of the heart, Werber says. “If you look at the heart of a dog that died from heartworm, they might have hundreds of worms,” he says.


How do dogs get heartworm?

By being bitten by an infected mosquito. The bug injects heartworm into your dog or cat when it takes a bite. It takes about five months for the larvae to mature into adult heartworms, which is why puppies that are five months or younger can’t be tested—they wouldn’t test positive even if they were bitten by an infected mosquito, Werber says. The heartworms live for five to seven years, and dogs may have up to 300 worms in their system at a time.


What are the symptoms of heartworm?

Initially, as the worms start crowding around your dog’s heart and lungs—, the only symptom is a cough. As it progresses, the heartworm will take over the lungs, causing your pup to become winded and out of breath as he runs or climbs the stairs. As the heartworm becomes more advanced, it could cause fainting because there isn’t enough blood getting to the brain; at this point, your pup will start retaining fluids. If not treated, heartworm can be fatal.


How is heartworm treated?

After confirming the diagnosis, your vet will need to kill all the adult worms. This can be done a couple of ways, depending on the severity of the heartworm. For example, an injectable, arsenic-based drug called Melarsomine might be administered at a vet hospital. The dog is given two or three injections, which can take up to three months to administer. The pup is typically hospitalized for a few days after treatment to restrict exercise, as physical movement and exertion increases the rate at which the heartworms multiply and causes damage to the heart and lungs. Your vet may also give your dog  preventative medication for two months prior to the injection to help improve the chances of treatment success, according to the American Heartworm Society. In severe cases, dogs may need surgery to remove the heartworms from his heart and lungs.


How do you prevent heartworm?

Heartworm is easy (and affordable) to prevent. There are various methods including monthly pills or chews, an injection that lasts for six months, and other options, Werber says. A year’s supply of preventative heartworm medication will cost between $35 and $80, depending on the dog’s weight. On the flip side, treating a dog with heartworm can range from $300 to $1,000. “Not only is heartworm dangerous, but it’s also costly,” says Werber. “Prevention is the way to go.”



Danielle Braff

Danielle is a freelance writer who loves taking walks with her 4-year-old cocker spaniel, whom she drags around Chicago multiple times a day. She and her husband also have two cats and two daughters.