Heartworm in Dogs - Prevention & Treatment

Heartworm Disease

A dog gets heartworms if they are bitten by a mosquito infected with the parasitic worm Dirofilaria immitis, which then enters the dog's blood stream. Heartworm isn't contagious and an infected dog can't transmit it to another pet; this disease can only be spread by mosquitos that carry the parasite. 

Don't make the mistake of believing that your dog is at low risk of heartworm disease; there have been reports of heartworms in all 50 states, and it is particularly in the area that lies between New Jersey and the gulf of Mexico. They can even be found along the Mississippi River and its major tributaries. 

If your pup has been bitten by an infected mosquito, the worms will grow into adults, mate, and produce offspring while living in your canine companion's heart, lungs, and blood vessels. 

Heartworm Prevention for Dogs 

Our vets at Dells Animal Hospital can't overemphasize the importance of heartworm prevention, as it is far superior to treatment of heartworm disease. If you have not already created a prevention plan for your dog, we recommend contacting your vet as soon as possible to do so. 

Typically, heartworm prevention is administered through a monthly medication prescribed by your vet. 

Signs of Heartworm Disease in Dogs 

Common symptoms of heartworm disease in dogs include:

In some rare and very severe situations, dogs can develop caval syndrome, an acute phase, severe form of heartworm disease.

This condition is most often seen in dogs that are heavily infected with heartworms. It can cause your pup to collapse suddenly and potentially die without immediate surgical intervention. This is why it's critical to contact your vet immediately if you notice your dog exhibiting any signs of heartworm disease. 

Treating Heartworm in Dogs 

In situations where preventive measures aren't effective at preventing infection, there are treatment options available for your dog. However, all of these options have potentially serious side effects that may cause health complications, though fatalities are rare. 

Heartworms are undetectable until at least five months after infection, which means many dogs already have advanced heartworm disease by the time they are diagnosed and require fast, intensive treatment. 

In rare circumstances, heartworms can severely damage a dog's internal organs. By the time the condition is found, it's better to treat the damage and keep the dog comfortable rather than taking additional risks related to trying to kill the heartworms. Dogs in this advanced condition are usually only expected to live for another few weeks or months. 

Thankfully, a new medication has been developed for killing adult heartworms while having fewer dangerous side effects. Melarsomine is an injectable drug that kills adult heartworms in dogs and is administered through multiple injections.

Typically, you'll need to wait 30 days after the first injection of Melarsomine to bring your dog back to your veterinarian for two more injections, which will be administered 24 hours apart. Antibiotics will also be prescribed to combat any infectious bacteria the heartworms may be carrying. Most dogs with heartworms can now be successfully treated with Melarsomine injections.

Your dog will also receive treatment to kill juvenile heartworms (microfilaria) either before or after their Melarsomine treatment. Your dog may need to spend the night in the hospital for observation on the day this treatment is administered.

What to Do After Your Dog Has Been Treated for Heartworms

Your dog must be allowed to rest following its injection. Heartworm treatment in dogs kills the adult heartworms within a few days, but further complications can occur while their corpses are decomposing.

It can take several months for the heartworms to be reabsorbed into the patient's bloodstream. Most post-treatment complications arise from these fragments of decomposing heartworms, so to minimize this risk your dog must not be allowed to exercise and should be kept as quiet as possible for the first month following treatment.

You'll likely hear your dog cough frequently for seven to eight weeks following injection. If this cough persists beyond this or is especially severe, as well as if your dog is demonstrating shortness of breath or fever, contact your veterinarian right away.

The Side Effects of Heartworm Treatment in Dogs

Heartworm treatment can cause serious complications for your pet's health and can potentially be toxic to the dog’s body. Many dogs experience soreness and swelling at the site of their injections.

The most severe side effects are related to a large number of worms suddenly dying. You must contact your vet immediately if your dog is panting excessively, has difficulty breathing, is suddenly lethargic or collapses, begins to reject their food, begins to vomit, or develops diarrhea.

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.