Mosquito Bites in Dogs

Mosquitoes might not seem to be a big problem for furry animals like dogs and cats, but your pets can still get bitten in areas with only thin hair coverage, such as the nose and ears. Dogs and cats experience the same itching and irritation caused by mosquito bites as humans, however a more serious concern is the spread of mosquito-borne diseases, especially heartworm. Heartworm is a parasite that causes life-threatening heart and lung infection in dogs and sometimes cats. It is carried from one animal to another via mosquitoes and it is relatively common in the United States. Protecting your dog or cat from mosquito bites is the best way to reduce the risk of heartworm infection. Mosquitoes pass through several stages in their life cycle. The eggs are laid by an adult female. She will choose a site close to water since mosquito eggs need water exposure to hatch; however the eggs can survive for several months unhatched if moisture is not present. The larva, sometimes called the “wriggler,” is a small worm that lives and feeds in the water, coming to the surface to breathe. The pupa or transition stage takes place just before the adult mosquito emerges. This phase is called the “tumbler” stage; the pupa remains in the water, but does not feed and develops a hard case that protects the developing adult fly. Shortly after emerging, mosquitoes will take to the air in the form that is best known. The females will bite humans and other animals such as dogs and cats, often spreading blood infections from one host to another. The entire mosquito life cycle usually takes about two weeks, but in ideal breeding conditions with high moisture levels, it may be as short as four days. Over the course of the summer, thousands of mosquitoes will be born and have the potential to bite and infect your dog or cat. Outdoor animals are more at risk, especially dogs or cats that spend a lot of time close to swampy areas or stagnant water.

Mosquitoes can be a nuisance for dogs and cats just as they are for humans. The bites cause itching and irritation, but more importantly they can also spread serious bacterial and parasitic infections.

When dogs and cats are bitten by mosquitoes, they experience the same itching and irritation as humans. The following symptoms could indicate mosquito bites.

• Constant scratching
• Rubbing ears or nose against a rough surface
• Red welts similar to mosquito bites in humans

• Coughing
• Respiratory difficulty
• Lethargy or depression
• Intolerance to exercise
• Lack of appetite or weight loss
• Vomiting (cats)

Types

These are some of the many different types of infection that can be carried by mosquitoes.

• Heartworm
• West Nile Virus
• Eastern Equine Encephalitis

Heartworm is the most common concern for dogs and cats.

It’s impossible to eliminate all mosquitoes, but these are some factors to take into consideration.

• Standing water around the house
• Animal water bowls or troughs
• Bird bath
• Any ornamental pond
• Untreated pool
• Seepage from a septic tank
• Water pooling in a tarp cover
• Water pooling in a driveway pothole
• Broken screens
• Night lighting

Mosquito bites can be diagnosed based on signs of itching and irritation as well as the presence of mosquitoes. Bites that carry infection are undetectable from those that don’t, so heartworm is only found through regular testing, or when symptoms of illness are already present. 

A small blood sample can be used to detect the presence of heartworm-related proteins. It takes six months for an animal to test positive for infection, so it’s recommended that dogs be tested at least once annually after they are seven months old. Cats are not as typical a host for heartworm; the infection is less common and different testing regimes may be recommended by different veterinarians. In cats, few worms reach the adult stage, however the larvae can still cause fatal and sometimes sudden illness, so it’s important to get your cat tested often too. If your dog or cat tests positive for heartworm, chest X-rays or further tests may be ordered to evaluate the extent of the infection.

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Insect repellent is often used to reduce mosquito bites in humans, but it can be unsafe for dogs and cats. Any human designed spray, especially those that contain DEET, may be toxic and should be avoided. Choose a repellant that is tested specifically on your pet, preferably with the advice of a veterinarian. Environmental repellants such as sandalwood or citronella candles may be more advisable if you cannot find a spray that is safe for pets.

If your dog or cat is suffering from severe discomfort related to mosquito bites the veterinarian may be able to prescribe or recommend a treatment to reduce the itching. Otherwise, no treatment is necessary and signs will quickly resolve. 

Dogs that test positive for mosquito-borne heartworm infection are usually treated with an arsenic-containing medication given in small doses over the course of several months. This medication is not safe to use in cats. No treatment is currently available for cats diagnosed with heartworm infection. However, monthly preventive medication can be given to both dogs and cats and is usually effective at eliminating the risk of infection.

Individual mosquito bites will heal in dogs and cats, but continued exposure increases the risk of infection. Taking steps to make your house and yard as mosquito free as possible in the summer months can reduce the chance that pets will be bitten by disease carrying insects. Since no mosquito elimination is foolproof, the best way to manage heartworm infection is with medication and regular testing. It’s important to be consistent and give each dose at the same time each month, since missed or late doses can impact the effectiveness of the treatment. Pets should be tested before beginning a treatment plan and after any lapse in medication.