Heartworm in Dogs: What You Need to Know



Everyone has heard about heartworms and may even have your dog on monthly prevention. Not everyone actually knows what heartworms are and how they can affect your dog. This article is everything you need to know about heartworms and what you can do to keep your pet healthy and happy.

What are heartworms?

Heartworms are parasites that live in the blood vessels, heart, and lungs. The worms can cause very deadly heart and lung problems.


How do dogs get heartworm?

Dogs and cats can only get heartworms from being bitten by a mosquito that contains baby heartworm (microfilaria).


Mosquito bites infected animal transmits microfilaria (baby worms)

The life cycle of heartworm can be very complicated. The simplified version of this complex life cycle is a mosquito bite an animal that has heartworms and during their blood meal ingests baby heartworm. This baby heartworm grows up to teenage heartworm in the mosquito. The mosquito then bites another animal and injects this teenager's heartworm into the new animal where the heartworm can grow up to be adult heartworm. The adult heartworms can mate and reproduce in the animal.

7 months gestation period (average)

The life cycle from reproduction until adult heartworm takes an average of 7 months. In the adult stage, a heartworm can live in the heart lungs and blood vessels. Sometimes heartworms are found in unusual places such as skin, eyes, and internal organs. Anywhere that blood is heartworm can be. Microfilaria can be found in the blood. Usually, when a dog that has heartworms has their blood drawn, you can see these baby heartworms swimming around in the blood under a microscope.


Can live 5-7 years in dogs

Adult heartworms can live for 5 to 7 years in a dog. When these worms move around, they are causing damage to the heart, lungs, and vessels. This damage causes all the signs associated with heartworms.

Swollen belly

Heartworms disease progresses to a more severe stage will show up with a swollen belly. The swollen belly is due to fluid accumulation in the abdomen. The worms are taking up space in the vessel, which limits the amount of fluid that can circulate in the body. This buildup of fluid will get pushed out of the vessels and into the abdomen.


Caval syndrome (cardiovascular collapse)

In end-stage heartworm disease, they will have a condition known as caval syndrome. In caval syndrome heartworms fill-up the vena cava, the vessel that brings blood back to the heart severely limiting blood flow to the body. During caval syndrome, a dog will have labored breathing, pale gums, and dark bloody or coffee-colored urine Caval syndrome is an emergency and should be taken to the veterinarian immediately. Many times, even with prompt veterinary intervention, dogs in caval syndrome will die.

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