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Heartworms are caused by a parasite called Dirofilaria immitis whose larval form is carried by the mosquito. The  life cycle of the heartworm is rather complicated and beyond the scope of this discussion, but what is important to know is that when a mosquito carrying the right larval stage of heartworms bites an unprotected dog, the larva are injected into the dog where they travel to the heart and grow into adult worms.  The adult worms can reach 12 inches in length and a heavily infected dog may have over 200 adult worms in its heart and surrounding blood vessels. It doesnít take much imagination to understand how this can be fatal to the dog!  Heartworm disease is a major cause of death in unprotected dogs, especially in the south where mosquitoes are so prevalent, but cases have now been reported in every state. Even a strictly indoor dog is at risk for heartworms, as it only takes one mosquito bite to cause infection.

Death from heartworms is a very unpleasant way to go. As the disease progresses the dog develops cough, shortness of breath, and weakness as the heart struggles to pump with its burden of worms. As the number of worms in the heart increases, the worms migrate into the large vein called the vena cava where they cause a condition called caval syndrome which frequently results in liver failure and death within a few days. Worms in the pulmonary blood vessels (going from the heart to the lungs) cause chronic heart failure and may result in sudden death from blood clots and bleeding into the lungs.  

Even dogs in the early stages of heartworm disease, who show no symptoms yet, are already having internal damage.

Once a dog has heartworms, treatment with a drug called immiticide usually gives the dog the best chance at recovery. Although immiticide is a very potent drug and treatment with it carries a degree of danger, most dogs will survive if treatment is begun early enough. The drawbacks are that immiticide does carry the risk of causing serious illness or even death and the fact that treatment is expensive and requires that the dog be kept very quiet for several weeks after treatment.

The good news is that nearly all cases of heartworms can be PREVENTED by giving your dog a medication prescribed by your vet, once a month, every month. That is a small price to pay to prevent this life threatening disease and no responsible dog owner would fail to do this. The preventative medication kills the larval stage of the heartworm before it can develop into an adult. It does not kill the adult worm, so if your dog has adult heartworms already the preventative will not kill them. In that case your vet will outline a course of action to treat your dog based on how far advanced the disease is. The presence of adult heartworms is determined by performing a simple blood test that your vet can do in the clinic.

Remember, heartworms are PREVENTABLE! And even if your dog already has heartworms, it is treatable, although prevention is much better. So if you have not had your dog on monthly preventative, have him tested for heartworms as soon as possible and follow your vetís recommendation for prevention, or if needed, treatment. And be certain to give the preventative once a month, EVERY MONTH. Most forms of preventative are given by mouth although some forms are applied to the skin where it absorbs into the body. If you give the oral form, be sure your dog actually takes it. Most dogs like the taste of the tablets, but a few will spit them out!

Many of the adult dogs we get at Raven Woods have heartworms. Due to the high cost of treatment we are not able to treat each one with immiticide. We treat as many as possible and we keep every dog on monthly preventative to prevent new infections.

Your donation to our heartworm treatment program will help us to treat more dogs and give them the chance at the healthy life that they deserve. We greatly miss our friends who died from heartworms before we could get them treated--Julius, Pittunia, Kelly Sue, Onyx, Joe Pit Bull, and Skinny Minnie. This article is dedicated to a day when no dog will die from this terrible but preventable disease.

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