Heartworm disease is a serious condition that affects dogs and other animals.  It is spread by mosquitoes and it occurs in all fifty states in the U.S.  Left untreated, it can be deadly.


The heartworm life cycle

Heartworms have a life cycle that depends on the mosquito and a host body.  The cycle begins when an adult female heartworm releases her young into the bloodstream of a host body, such as a dog.  Then a mosquito must bite the dog, taking in blood and microfilariae (the immature heartworms).  It takes about two weeks for the microfilariae to mature to a larval stage where they can infect another animal.  When the mosquito bites another animal, such as a dog, the larvae enter the bloodstream and the dog becomes infected.  Over the course of about six months, the larvae will work their way to the dog’s lungs and heart and become adult worms.  They can live for up to seven years and grow to be up to 10-12 inches long.  A dog can have as many as 250 heartworms in his heart and longs.


Symptoms of heartworm disease

Symptoms of heartworm disease aren’t usually noticeable until the dog is well past the early stages of infection.  Once a dog is heavily infested with heartworms he can have a mild but regular cough, be reluctant to exercise, tire easily, have a loss of appetite, and lose weight.


The heartworm test

Dogs should be tested for heartworms annually.  The test is a simple blood test that detects an antigen that indicates heartworms are present or the microfilariae in the bloodstream.



Luckily, there are a number of good heartworm preventives available today.  Heartgard Plus, Tri-Heat Plus, and Iverhart Max all contain ivermectin and will kill microfilariae in a dog’s bloodstream, thus preventing heartworms from developing.  However, ivermectin products should not be used by collie-type dogs such as Collies, Shelties, and Border Collies.  Some people suggest that ivermectin should not be used on any herding dogs.  Some of these breeds have a mutation in the MDR1 gene which causes ivermectin to be toxic to them.


You can also use Interceptor or Sentinel to prevent heartworm.  These medications contain milbemycin oxime.  Revolution contains selamectin.  Advantage contains moxidectin.  All of these preventives will keep heartworms from developing in your dog after a mosquito has bitten him.  There are no preventives which can guarantee that your dog will not be bitten or receive heartworm larvae into his bloodstream.  Preventives work by killing off the larvae that is in your dog’s bloodstream each month before it can go to your dog’s heart and lungs.


Products for heartworm prevention must be obtained by prescription.



If your dog does develop heartworms there are treatments but they can be difficult for your dog and they are costly.  It is much easier to prevent heartworms than it is to treat them later.



Heartworm disease is a serious and often deadly condition in dogs.  Talk to your veterinarian about which method of heartworm prevention is best for your dog so you can protect him.


Article by Nancy Cope, owner of the popular online dog boutique, Pampered-dog-gifts.com where you will find a wide range of products to pamper your pooch.  Select from gourmet treats, gift baskets, designer apparel, toys and more.

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