Repel Mosquitoes to Help Prevent Heartworms
- Dallas Duncan
- Jul 22
- 5 min read
Northeast Georgia pet owners are probably familiar with our state bird. No, not the brown thrasher: the voracious, ever-hungry bloodsucking mosquito.
Northeast Georgia pet owners are also likely familiar with their vet’s recommendation to put their pets on heartworm prevention, advice based on the prevalence of that aforementioned insect. Heartworm disease is mosquito-borne, meaning the fewer mosquitoes in your yard, the lower the risk of your pet contracting heartworms, especially if they’re also on a monthly or annual preventative.
“We’ve got over 20 different mosquitoes that we’ve identified in the US that can infect with heartworm disease,” says Dr. Chris Duke, DVM, past president of the American Heartworm Society. “The mosquito is the vector that spreads your disease. We can’t get rid of every mosquito, but we try.”
Veterinary entomologist Annie Thompson, who is based in Summerville, Georgia, says that the main mode to get rid of mosquitoes is removing standing water around homes and yards.
“Mosquitoes’ first few stages of life are aquatic, and so if you don’t have any standing water you’re less likely to have them,” Thompson says. “They can lay up to 200 eggs at a time, and they only need as much water as a bottle cap. Even rain collecting in trash, they can lay their eggs in that.”
Drainage pans under potted plants can also provide real estate for mosquitoes to take up residence.
“Pet water bowls outside — make sure you’re dumping them and refilling them, because mosquitoes can go from an egg to an adult in a week. It needs to be dumped out really regularly to avoid breeding mosquitoes,” Thompson says. “Also, you can use Mosquito Dunks.”
Dunks contain a bacteria deadly only to mosquito larvae, making them effective control methods for water troughs or other spots of standing water that can’t be dumped or refreshed as easily.
Thompson says pesticide companies that offer mosquito spraying can be effective as well, provided they are applying to label instructions, avoiding flowering plants, and focusing on areas that mosquitoes may be resting. Mosquitoes can be dissuaded from biting pet owners by using repellants that contain DEET or picaridin. Thompson says for folks who prefer a more natural approach, repellants with oil of lemon eucalyptus have also been shown to be effective, but are not as long-lasting between applications as DEET and picaridin.
“Basically the ‘smell’ of [DEET] works by confusing the receptors that a mosquito uses to detect people. They detect us by smelling our carbon dioxide and sensing our body heat,” she says.
At this time, there are no safe mosquito repellants approved for use on pets, which is why a combination of environmental control and heartworm preventatives is a top way to reduce pets’ risk of contracting the parasite.
Heartworm Positive
According to the American Heartworm Society, in 2022, most Georgia veterinary clinics saw 50 to 100-plus positive cases of heartworm, which can be detected in a dog or cat at the third larval phase. There are five stages to a heartworm’s life cycle, which is split between developing in a mosquito vector and an animal host. L1 are microscopic baby heartworms, called microfilaria, which appear as “little wigglers” under the microscope in a blood sample, Duke says. Because they’re so small, L1 heartworms can be transmitted through a mosquito’s mouthparts when the mosquito takes a blood meal from an infected pet. Once inside the mosquito, its stomach juices stimulate the microfilaria to molt, marking the next phase of the heartworm’s life cycle, L2 larvae. These larvae then migrate to the mosquito’s salivary glands and molt to L3 size, where — when the mosquito next takes a blood meal from an uninfected pet — its saliva transmits the L3 larvae, which then develop in the host to L4.
And the final L5 stage of heartworm infection?
“They’re huge worms. They’re up in the pulmonary cardiac tissue,” Duke says. “What you have to do — if there’s a most important part of this whole cycle — is breaking that, blocking, intercepting that L3 that comes off the mosquito so that it can’t get into a dog.”
He says it takes about 45 to 60 days for the heartworm to grow from L3 to L4, so even one missed month of heartworm preventative can put a cat or dog at risk.
“[Dogs and cats] will live with it asymptomatically for a window of time, but eventually heartworm disease is fatal,” says Dr. Tyson Strickland, DVM, owner of Comer Veterinary Hospital. He adds that other conditions associated with heartworm disease can crop up, and even if a positive case is successfully treated, it can shave years off that pet’s life or predispose an animal to future heart and lung issues. They will also likely retain heart damage or scarring.
Comer Vet’s veterinary team recommends dogs and cats receive an annual heartworm test to ensure their preventions are effective and that they’re not infected with a resistant strain. Strickland says the recommended treatment process for Comer Vet patients that test heartworm-positive is to undergo a series of three melarsomine injections.
“We’ll also start them on a doxycycline antibiotic,” he says. “There’s a bacteria that lives within a heartworm that helps it thrive. That antibiotic is gonna help weaken that heartworm. We’re gonna do that a month prior to giving that first injection of melarsomine. We’re also gonna start them on a heartworm medication at the same time that’s also gonna start that process of weakening that heartworm.”
A month after receiving their first melarsomine dose, Strickland says patients return for the second and third injections, given within 24 hours of each other. Regular prevention will begin again, too. Strickland cautions pet owners that if their dog has undergone a heartworm treatment, it’s vital to keep their pups quiet and resting.
“As the heartworms are breaking down, we don’t want a piece to dislodge and cause an embolism as well. That’s another risk factor for heartworm treatment,” he says. “Typically, several months later, we’re gonna come back and test that, and we’ll make sure that it is now heartworm-negative.”
Duke says that cats are at a lower risk for contracting heartworms because their immune systems, in most cases, handle the larvae. He says that cat owners should still consider heartworm prevention, because it protects them just in case their immune systems can’t. Cats also have smaller hearts than dogs, which means one or two heartworms in a feline can cause more damage faster than they would in a canine.
“We definitely recommend it being a preventative versus a treatment. It’s also a lot cheaper to prevent it than it is to treat it once you have a dog with heartworm disease,” Strickland says.
A number of options for heartworm prevention are available through Comer Vet, including monthly preventatives like chewable “treats” and, for eligible dogs, the annual ProHeart injection. Strickland says some preventatives also work against internal parasites, fleas, and ticks, so pet owners can get more full-spectrum coverage against disease-causing pests.
“It’s a preventable disease in the first place, so these animals don’t have to die prematurely from lack of prevention,” Duke says.
To schedule your dog or cat’s annual heartworm test at Comer Vet, please give us a call at 706-783-5111 or request an appointment through our online form.