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10 Dangers of Fleas, Ticks and Mosquitoes

Jack Russell Terrier in tall grass at risk of parasites
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Fleas and ticks are among the most common external parasites in pets. Pesky mosquitoes also enjoy feasting on dogs and cats. Not only do fleas, ticks, and mosquitoes cause intense itchiness, but they also transmit diseases that can make pets seriously, and sometimes fatally, ill. 

All pets—even indoor pets—are at risk of fleas, ticks, and mosquitoes. These little bloodsuckers can hitch a ride inside on you or a pet and make themselves at home. That’s why veterinarians often recommend year-round parasite protection for pets, such as Simparica Trio for dogs or Revolution Plus for cats.

Keep reading to learn more about the dangers fleas, ticks, and mosquitoes pose and how to protect your pet (and yourself).

10 Dangers of Fleas, Ticks and Mosquitoes

Indoor cat scratching and itching

Despite their tiny size, fleas, ticks, and mosquitoes can pose significant dangers to our pets.

Flea allergy dermatitis

Dogs and cats aren’t just irritated by flea bites. They can also be allergic to them. A flea’s saliva has substances like enzymes and histamines that a pet’s immune system recognizes as foreign, triggering an immune reaction. This reaction leads to symptoms like intense scratching and biting of the skin, crusting, hair loss, hot spots, and secondary infections.

Flea allergy in dogs and cats is typically diagnosed if your pet has skin allergy signs and their veterinarian sees flea dirt or adult fleas on your pet’s coat. It is treated with products that will remove fleas from the skin and reduce irritation and itching.

Year-round flea control with oral or topical products is critical to preventing flea allergy dermatitis.

Flea-borne diseases

Fleas are notorious for transmitting diseases that can make pets ill. One such disease is murine typhus, caused by the bacteria Rickettsia typhi. Another disease is bartonellosis (‘cat scratch disease’), caused by the bacteria Bartonella henselae. Fleas also spread the plague.

Tapeworm infection

Pets can get tapeworms by swallowing adult fleas that carry tapeworm larvae (immature tapeworms). These larvae then develop into adults in a pet’s digestive system. The segments of an adult tapeworm resemble grains of white rice and exit the body in a pet’s poop. Tapeworms are easily treated with a drug called praziquantel, which kills the tapeworms in the intestine.

Flea infestations

As if flea bites aren’t bad enough, flea infestations can be even worse. Fleas can’t fly, but they can jump up to 2 feet, a very impressive feat given their tiny size. This jumping ability means fleas can jump from pet to pet and even from pet to human. So, if one of your pets has fleas, it may not be long before all of your pets and you begin feeling itchy from flea bites.

Adult female fleas can live on a pet’s skin for up to two months and lay 40 to 50 eggs daily; that’s thousands of flea eggs! When these eggs fall off your pet, they find hard-to-reach places like cracks and crevices to lay dormant, wrap themselves in a cocoon, and develop into adults. 

Once fleas are fully formed into adults, they’re ready to jump onto the nearest host, and the cycle begins again. Eliminating a flea infestation can take months because you must break the flea’s life cycle and get rid of all flea life stages in your home.

Tick-borne diseases

Ticks can carry numerous infectious diseases in their little bodies that affect pets, such as Lyme disease, Rocky Mountain spotted fever, anaplasmosis, ehrlichiosis, and babesiosis. Generally, tick-borne diseases are more commonly seen in dogs than cats.

Lyme disease in dogs is caused by the bacteria Borrelia burgdorferi, which is carried by either the black-legged tick or deer tick. It causes symptoms like joint pain, fever, and lameness. Lyme disease in cats is rare. 

Rocky Mountain spotted fever, caused by the bacteria Rickettsia rickettssii, is carried by several ticks, including the Lone Star tick. Symptoms include fever and generalized pain. Anaplasmosis is caused by two Anaplasma bacteria carried by multiple ticks, including the brown dog tick. Anaplasmosis symptoms include fever and joint pain.

Tick-borne diseases are treated with antibiotics. Other medications, such as pain medications, may be needed. Pets with severe symptoms may require hospitalization.

Tick paralysis

Tick paralysis in dogs and cats is caused by toxins in a tick’s saliva that attack the nervous system. An affected pet’s muscles gradually become paralyzed, leaving them unable to walk, eat, and breathe. Ticks most associated with tick paralysis are the American dog tick, Rocky Mountain wood tick, deer or blacklegged tick, and Western blacklegged tick.

Removing the tick removes the source of the paralysis, and pets often recover quickly once they are treated. However, some pets may have to be hospitalized for severe symptoms.

Heartworm disease

Heartworm disease tops the list of mosquito-borne diseases in pets. Mosquitoes carry heartworm larvae that enter a pet’s bloodstream during a mosquito bite. These larvae migrate through the body, taking about 10 weeks to develop into adults. Adult heartworms migrate to the heart and lungs, where they can cause serious trouble.

Heartworm in dogs causes vague symptoms like fatigue and cough. More severe symptoms, such as weight loss and belly distension, occur with a high worm burden and indicate congestive heart failure. 

Heartworm in cats is not as common but is much more severe than heartworm in dogs. It causes symptoms like lethargy and coughing. Unfortunately, cats with heartworm can develop a fatal condition called heartworm-associated respiratory disease (HARD), caused by a severe inflammatory reaction when heartworms die.

Caval syndrome

Caval syndrome occurs in dogs with chronic heartworm disease. It is caused when the burden of heartworms in the pulmonary artery is so high that the worms migrate to the caudal vena cava (a major blood vessel for the body) and the right side of the heart. Blood flow through the heart becomes blocked, and affected dogs have symptoms like difficulty breathing, heart failure, and weakness. Caval syndrome can be fatal within hours without surgery to remove the heartworms.


Anemia is blood loss. Fleas and ticks can cause anemia because they feed on the blood of their hosts. Heavy flea and tick burdens can lead to significant blood loss, which can be life-threatening in puppies and kittens. Signs of anemia in dogs and cats include weakness and pale gums.

Treatment for anemia depends on the severity. Anemia caused by fleas is treated by removing the fleas and preventing another flea infestation. Severe anemia may require hospitalization and a blood transfusion.

Hair loss

Bites from fleas, ticks, and mosquitoes can cause intense itchiness. Constant biting, scratching, and licking at the bite area can lead to hair breakage and eventual hair loss.

How to Protect Your Pet from Fleas, Ticks and Mosquitoes

Pet parent with dog and cat outside

Protecting your pet from fleas, ticks, and mosquitoes is essential and requires a multi-pronged approach that involves treating your pet and the inside and outside of your home.

The strategies listed below offer easy, convenient, and affordable ways to protect dogs, cats, and your household from pesky (and dangerous) parasites. Be sure to speak with your veterinarian to choose the most appropriate flea, tick, and mosquito protections for your pet and location.

Treating your pet

Year-round flea and tick control: This is the best strategy for preventing flea and tick infestations. All dogs and cats in your home must be on a flea and tick control product. These range from over-the-counter flea and tick sprays or collars to prescription oral and topical preventatives, such as Simparica chewables for dogs and Revolution topical treatments for dogs and cats.

Year-round heartworm prevention: It’s important to give your pet a monthly heartworm preventative, even during winter. Year-round protection is essential to prevent a heartworm infection. Ask your vet about your heartworm preventative options and whether you should consider a broad-spectrum combination preventative, such as Simparica Trio for dogs or Revolution Plus for cats, which protects against fleas, ticks, and heartworms in one convenient monthly dose.

Regular tick checks: Check your pet for ticks anytime you go outside, especially if you stroll through the woods, where ticks love hiding in tall grasses and on trees.

Flea combs: Flea combs are an inexpensive way to remove fleas and flea eggs from your pet. Use a flea comb along with a flea and tick control product.

Mosquito repellent: Pet-safe mosquito repellents are available to protect your pet from mosquitoes when outside. Ask your veterinarian for recommendations for pet-safe repellents.

Stay indoors during peak hours: Mosquitoes are most active at dawn and dusk. Keeping your pet indoors as much as possible, especially at dawn and dusk, will help protect your pet from mosquitoes.

Treating the environment

Wash your pet’s bedding: Your pet’s bedding is a favorite hiding spot for immature fleas. Wash the bedding regularly in hot water to kill the fleas.

Vacuum regularly: Regular vacuuming, especially in hard-to-reach cracks and crevices, will remove fleas from their hiding spots. Empty the vacuum bag outside to prevent another flea infestation.

Remove outdoor flea and tick hideouts: Fleas and ticks love to hide in tall grasses, weeds, piles of leaves, and other organic debris. Removing their hiding places, such as by weeding and regularly mowing your lawn, will help keep them away from your home.

Remove standing water: Mosquitoes like to breed where there’s standing water. Remove sources of standing water outside your home, like pool covers and water buckets.

Repair window screens: Window screens with holes allow easy entry inside for mosquitoes. Repair any screens that are broken.

Hire a professional exterminator: If treating your home is too much work for you, consider hiring a professional exterminator. Make sure that the products they use are safe for pets.