Wednesday, January 29, 2020

Heartworm Disease in Pets


What is Heartworm Disease?

Heartworm disease is a potentially fatal blood parasite that restricts blood flow and can damage the heart and lungs.  

How is Heartworm Disease transmitted?

Heartworm disease is transmitted by mosquitoes year round.  An animal that lives or spend time outdoors and animals that live exclusively indoors are both at risk of contracting Heartworm disease. The female heartworm produces microfilaria which are small baby worms. The mosquito would have to bite a positive animal that has microfilaria circulating in the animal’s bloodstream and essentially picks up these small worms. Over the course of two weeks the microfilaria mature and when the mosquito then bites an animal deposits these on the surface of the animal’s skin. After the larvae migrate into the host it will take 6 months for them to mature into adult heartworm.  

What are the clinical signs of Heartworm Disease?

Sometimes animals can have no clinical signs of heartworm disease. Other times they can range from coughing to even death.

Common Clinical Signs in Dogs Common Clinical Signs in Cats
Coughing Coughing
Exercise Intolerance Vomiting
Weight loss Weight loss
Labored Breathing Death
Decrease in Appetite


Should your animal be tested?

A puppy less than 7 months of age can be automatically started on Heartworm prevention.  The reason for this is it takes about 6 months for a dog to test positive. This means that when your animal turns one year old they should be tested by your Veterinarian to make sure they were not exposed during the time they were not on heartworm prevention.

If your dog is over 7 months of age and is not on heartworm prevention they need to be tested prior to starting the heartworm prevention and once again in 6 months to make sure they were not exposed during the time they were off of prevention.

Cats should be tested prior to being placed on Heartworm prevention.  It is recommended that an antigen and antibody test is performed. This is checking to see if the cat was exposed to heartworm larvae. Radiographs and ultrasounds can also look for heartworm infection.

Why must my dog be tested if already on prevention?

Any type of prevention is never 100%.  Although Heartworm prevention is highly effective if your dog spits the pill out, doesn’t eat the pill or even if you miss a month they are at risk for getting Heartworm disease.  

Your animal tested positive.  Now what will happen?

After getting a positive reading your Veterinarian will send out more tests to confirm the diagnosis. Your animal should be restricted with exercise as soon as a positive is noted. This is because if your animal continues to exercise and increases their heart rate they have a higher chance of getting heart and lung damage. During this time your Veterinarian will stabilize your animal and start treatment. After the treatment has been finished it is recommended to recheck a heartworm tests 6 months later to confirm the treatment has worked.

Should your cat be on heartworm prevention?

Yes.  It is highly recommended that all cats whether indoor or outdoor be on heartworm prevention. Only one heartworm can be fatal to your cat. Cats should be tested prior to putting them on prevention.  It is very important that cats are on prevention because there is currently no approved treatments for cats. Your cat may only have 1 or 2 worms so the diagnosis can be difficult. If your cat is positive for heartworm it is important to discuss with your Veterinarian what the best options for long-term management of the disease are for your cat.

Additional benefits of heartworm prevention

Some heartworm preventions will also prevent against some intestinal parasites. Some of these intestinal parasites like Roundworm and Hookworms are zoonotic. This means that they can be transmitted from your animal to you.  

Schedule an appointment with your Veterinarian to discuss testing and prevention of heartworm disease for your pets to ensure their optimal health.

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