Protecting Your Dog or Cat from Mosquitoes

Lauren Jones, VMD
By Lauren Jones, VMD on Jul. 13, 2022
Protecting Your Dog or Cat from Mosquitoes

Mosquitos are small insects closely related to flies. Like flies, they have six legs and two wings, but mosquitos also have scales and have adapted long specialized mouthpieces. The female mosquito's proboscis, or mouthpieces, is able to pierce skin. Both male and female mosquito’s primary food is nectar or other sugar sources – similar to honeybees. Females also use their piercing mouth part to suck blood from animals – although not for nutrition purposes. Females require this blood meal in order to produce their eggs. Mosquitos will take a blood meal from birds, cold-blooded animals (like reptiles), and warm-blooded animals (like dogs, cattle, and humans).

There are over 3000 recognized species of mosquitos worldwide – and more are discovered every year.  Mosquito bites can be painful, itchy, and cause allergic reactions. It is the mosquito’s saliva that stimulates the immune system, leading to red, itchy bumps. However, mosquito bites are more than a general annoyance. Some mosquitoes can transmit serious, and often fatal, diseases – to humans and animals alike.

For our dog and cat populations, mosquitos are the required vector responsible for spreading heartworm disease. Globally, mosquitos are responsible for multiple human diseases, such as malaria and West Nile Virus. They are also responses for illnesses that affect food supply animals leading to weight loss, decreased milk production, and other afflictions. To minimize disease and decrease human and pet suffering, mosquito control is crucial in endemic areas.

Mosquitoes and Heartworm Disease in Dogs and Cats

Heartworm disease is a potentially fatal medical problem caused by the worm Dirofilaria immitis. Heartworm disease can infect many mammals, but canine species (dogs, coyotes, wolves, and fox), felines, and ferrets are most commonly affected. Heartworm has been diagnosed in all 50 states, but typically has higher incidence rates in hot, humid areas of the United States – most notably the Southeast, East, and the Mississippi River Valley.

Mosquitos are the required vector, or agent, responsible for the transmission of heartworm disease. A female mosquito transmits the microscopic, immature larval form of the parasitic worm to the host during a blood meal. The heartworm’s life cycle can take up to 9 months, resulting in adult heartworms up to 12 inches long, living in the vessels between the heart and lungs. Here, they cause a variety of symptoms including coughing, difficulty breathing, heart failure, weight loss, and can even cause sudden death. Cats are typically more resistant to heartworm disease, but have limited treatment options when they do acquire it. Luckily, we can protect our pets with monthly topical or oral preventative treatments, so they never develop heartworm disease.

Diseases Spread by Mosquitoes

Mosquitos can spread multiple diseases to humans and pets. Some of these diseases cause neurologic symptoms, while others cause flu-like illness or rashes. Mosquitos can carry and transmit protozoal, filarial, and viral diseases. The American Mosquito Control Association estimates over one million humans die from mosquito-borne illness every year. If you are concerned you may have acquired a mosquito-borne disease, contact your human healthcare provider immediately.

  • Malaria
  • Chikungunya
  • Dengue
  • Yellow Fever
  • Eastern Equine Encephalitis
  • St. Louis Encephalitis
  • LaCrosse Encephalitis
  • Western Equine Encephalitis
  • West Nile Virus
  • Zika Virus

Protecting Your Dogs and Cats from Mosquitoes 

Because of the serious nature of the diseases spread by mosquitos, protecting our pets is of utmost importance. Heartworm is the most common mosquito-borne disease in pets. Because of this, veterinarians recommend year-round preventative heartworm treatment for all dogs and cats. Even though the incidence of heartworm disease decreases during winter months, it never drops to zero. Most common heartworm preventatives include:

Heartworm preventatives work retroactively. This means a mosquito must bite and transmit immature larvae into a dog or cat, where they will circulate in the blood stream. The monthly heartworm preventatives work to kill any of these larval forms before they progress to the disease-causing adult form.

While heartworm preventatives are crucial for our pet’s health, methods of decreasing mosquitos in the environment are also important. These methods can decrease the spread of other diseases – to both humans and pets – as well as eliminating or decreasing the pesky, irritating, and painful attacks of mosquitos. Make sure to talk to your veterinarian to discuss the best heartworm preventative for your pet.

The mosquito’s lifecycle is short—only approximately 4-30 days, depending on species and environmental conditions. After a blood meal, female mosquitos lay eggs in water, which will typically hatch within 48 hours. The larval mosquito form continues to live in the water – feeding on microscopic organisms and debris in the water. It then enters a pupal stage similar to the cocoon metamorphosis of caterpillars becoming butterflies. The adult emerges and leaves the water, starting the process over again.

Knowing the lifecycle of mosquitos allows us to target different areas for the most effective mosquito control. Removal of standing water, or even sources of moisture, prevents female mosquitos from laying their eggs. Make sure to change your dog’s water dish frequently and drain areas with water that cannot be permanently eliminated. This is a simple and effective first step to mosquito control. Keeping screens and doors closed is also effective at keeping mosquitos outdoors. Ensure the yard free of tall weeds or grass and remove tires or junk from the area.

Birds, bats, and dragonflies are mother nature’s mosquito control. Encourage the predator species who eat mosquitos to frequent your yard. Dragonflies have a voracious appetite for insects and may be attracted to certain plants. Bat houses encourage a safe place for bats to congregate, aiding in bat conservation as well as mosquito control.

In addition, chemicals can be added to pools and other standing water that contain insect growth regulators. These are typically chemicals that affect the larval stage of insects, preventing maturation but not doing much against adult mosquitos. These are usually safe for mammals. Make sure to talk to a professional to choose the appropriate product that is safe for your family and pets.

Some plants may naturally repel mosquitos, although this shouldn’t be used as the primary deterrent. Typically, the oil in the plant, not the plant itself, is what repels insects, including mosquitos. Therefore, the leaves must be crushed for maximum efficacy – simply planting them in the garden won’t work the same.  Some plants to consider for this purpose include:

  • Citronella – this is also included in bug-repelling outdoor candles, torches, etc.
  • Lavender
  • Catnip - and your cat will love it, too!
  • Scented geraniums
  • Mint
  • Basil
  • Rosemary
  • Bee balm
  • Marigold
  • Floss Flower
  • Sage
  • Allium

Use caution and check with your veterinarian and the ASPCA’s Pet Poison website before using some plants. Some species, like allium, lavender, or citronella species, can have toxic effects in dogs and cats.

Some monthly pet preventatives can actually repel or kill mosquitos. Canine Advantix II and Vectra are two veterinarian-approved mosquito repellents for dogs – they have the added benefit of also killing fleas and ticks. These products contain permethrins, which are highly toxic to cats. It is important to only use products labeled and approved for the appropriate species.

There are a wide variety of products on the market to repel mosquitos on and around our pets. Always make sure you are using the product as directed and ensure that the product is species appropriate. Cats should never receive dog or horse products, and dogs should never receive horse or cat products. Talk to your veterinarian about any safety concerns regarding mosquito control. Use caution when using any over-the-counter products on your pet, as it may not be safe to use in combination with other monthly preventatives for fleas and ticks. While spray preventatives may seem enticing, they are never a replacement for veterinarian-approved and prescribed parasite control. In fact, they may do more harm than good.

Humans frequently utilize products containing DEET, which is an effective insect repellent. However, pets are sensitive to DEET and these products should never be used on pets without the specific direction of a veterinarian. DEET exposure and toxicity display primarily as neurologic changes and seizures, which can be fatal.

Natural and DIY Mosquito Protection for Your Pets

Pest control companies and “DIY-ers” can find a variety of products to use around the home (and not directly on our pets!)

Mosquito traps use scent attractants to draw and trap mosquitos. These can be pricey, depending on the product. Wind and airflow patterns can also decrease the efficacy.

Backyard spray and foggers can suppress mosquito activity for weeks. Professional applications may cost more, but can last longer and be safer for pets. Never use a fogger or spray with your pet around – wait the recommended period until the air has cleared to avoid any respiratory irritation. These types of repellents can also harm beneficial insects, like bees and butterflies, so use caution. 

Mosquito dunks produce proteins that are can be toxic to larva. This type of control usually has very little residual effect on the environment and may last up to 30 days.

Some essential oils and citrus sprays may repel mosquitos, but should never be used in close proximity to dogs and cats. These oils can cause respiratory irritation when inhaled and gastrointestinal complications if ingested.

Citronella products are known for their efficacy at repelling mosquitos. Citronella, if ingested, can cause illness in dogs and cats so always use caution with these products.

If Your Dog Is Bit by Mosquitoes, What Should You Do?

Sometimes, even despite our best efforts, pesky mosquitos will break through the barriers and bite our pets. Just like humans, some pets may experience painful, swollen, itchy, red, and raised bumps where a mosquito fed.

Talk to your veterinarian about using oral antihistamines, like diphenhydramine, to alleviate the itch. You can also consider over-the-counter products, like the soothing Douxo brand wipes, shampoos, mousse and serum products. Ask your vet before using any products, especially those containing steroids, such as cortisone, as it may have other side effects.

Seek immediate veterinary care if your pet stops eating, is lethargic, is vomiting or having diarrhea, or if they have a severe allergic reaction to a mosquito bite. Make sure to test your pet annually for heartworm disease and keep them on year-round preventatives. By keeping them parasite-free, we can let them live their best life!


Lauren Jones, VMD


Lauren Jones, VMD


Dr. Lauren Jones graduated from the University of Pennsylvania School of Veterinary Medicine in 2010, after receiving her bachelor's degree...

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