What Is Heartworm and How Do I Protect My Pet?

Heartworm infestation is a life-threatening pet health condition that can occur in both dogs and cats. These parasites are spread by mosquitoes and make their home in your pet's heart. Though found all over the world, they are most commonly found near large bodies of water.

Greyhound sleeping - not sick with heartworm
Photographer: Annie Spratt

How heartworm affects your pet

Heartworms can be very damaging to your pet. The majority of heartworm larvae will arrive in your dog or cat's heart about three months after entering the body. Here, they will grow rapidly and begin to produce microfilaria, which is then passed into the blood and picked up by other mosquitos. Adult worms can live between five and seven years in your pet's heart when left untreated.

As heartworms grow and multiply, they begin to block the normal flow of blood in your pet. In fact, female heartworms can grow up to two feet long. If you have a small dog or cat, it only takes a few worms to create a blockage. Furthermore, some pets, develop severe allergies to heartworms. In some cases, if a pet has acquired an allergy to these parasites, it can die suddenly even if it only had a few worms.

Common symptoms of heartworms

Symptoms of heartworm vary depending on how severe the infestation is, and your pet’s overall physical health and age. However, there are some warning signs that you can look for. If you see any of them, you should take your pet to a veterinarian immediately. The most common symptoms of heartworms in pets include tires easily, deep coughing, difficulty running and playing, weight loss, rapid breathing, Shortness of breath/difficulty breathing, fainting, bulging chest, anemia, nose bleeds, joint pain and shock.

Treatments for heartworm

Treatment for heartworms depends on any medical complications that may be present. Your veterinarian will thoroughly examine your pet and discuss treatment plans with you. However, if there are no serious medical complications, the main objective will be to kill all of the adult worms, microfilariae and begin prevention medication.

Your pet may need to be hospitalized so that your vet can make sure that there will be no complications following treatment. The most commonly used medicine to kill heartworms is Immiticide and is injected into your pet's muscle once per day for two days in a row. It is essential for you to keep your dog or cat calm for about two to three weeks after treatment. This will allow the body to rid itself of the dead worms. Other treatments that may be necessary include anticoagulants and/or surgery. Heartgard, Interceptor or Revolution can help prevent future infestations.

Breeds affected

Any breed of dog or cat can acquire heartworms if they are bitten by an infected mosquito. However, there are some animals that are more vulnerable to the condition than others. If your pet is not currently taking heartworm preventive, they are at risk. Other risk factors include pets that are kept outdoors or those who spend a lot of time in wooded areas. Pets who spend a lot of time around bodies of water, as well as stagnant bodies of water around your home and yard, increase the risk to your pet.

Spanial dog with kitten - breeds at risk for heartworm disease
Photographer: Jovana Askrabic

Heartworm affects

Heartworms can be very damaging to your pet. The majority of heartworm larvae will arrive in your dog or cat's heart about three months after entering the body. Here, they will grow rapidly and begin to produce microfilaria, which is passed into the blood and picked up by other mosquitos.

Adult worms can live between five and seven years in your pet's heart when left untreated. As heartworms grow and multiply, they begin to block the normal flow of blood in your pet. In fact, female heartworms can grow up to two feet long. If you have a small dog or cat, it only takes a few worms to create a blockage. Furthermore, some pets, develop severe allergies to heartworms. In some cases, if a pet has acquired an allergy to these parasites, it can die suddenly even if it only had a few worms.

Other problems that can result from heartworms include hypertension, blood clots, liver damage, kidney damage, aneurysms, pulmonary eosinophilic granulomatosis, acute vena cava syndrome, thromboembolism, and death.