Most dogs who have adult male and female heartworms also have microscopic heartworm babies called microfilaria (or stage 1 larvae) that circulate in the pet's blood stream.  A mosquito bites the pet and ingests the microfilaria along with it's blood meal.  Inside the mosquito, the stage 1 larvae molt into stage 2 larvae.  The mosquito then bites a cat or dog and injects the larvae into that pet's skin. This larvae stays in the skin 30 days (hence the use of once monthly heartworm prevention) prior to beginning it's 5 month journey migrating through the body on it's way to the pulmonary artery in the lungs.  The adult worm in a dog can be 12 inches long and will cause damage to the arteries, lung tissue, and heart.

Early in the disease, your pet may show no signs.  Once the disease progresses you can see coughing, wheezing, exercise intolerance, vomiting in cats, fluid buildup in the abdomen, or sudden death.

Diagnosis of heartworms in dogs is made by a simple blood test that takes only 10 minutes to run. The test will detect antigens which are like a chemical and are secreted by the adult worms. The worms must be at least 5-6 months old before they will be detected by testing. Yearly testing of dogs is recommended because it's better to catch heartworm disease early rather than waiting to see if signs develop.  Even if your pet is on prevention, you may have forgotten to give a tab or the pet may have spit out a tab without your knowledge. Testing in cats can be tricky because they may only have one worm that doesn't secrete much antigen.

The good news is that PREVENTION is safe, effective, and affordable. For as little as $4.00 per month, you can't afford NOT to prevent this disease.  Remember, prevention and treatment are two different things. Preventions such as Iverheart, Heartgard Plus, Interceptor, Sentinel, and Revolution are designed to keep your pet from getting the worms in the first place.  Treatment with Immiticide is designed to kill adult worms that your pet already has. Puppies that are started on prevention at 6 weeks and take it once monthly for life will never get heartworms.  Since a heartworm has to be at least 5 months old to show up on a test, puppies less than 5 months old do not need a test prior to starting prevention, but should get tested 6 months after beginning the meds.  Dogs 6 months and older (who have never been on prevention) need a test first.  If the test is negative, start prevention and retest 6 months later then regular yearly rechecks.

Cats can be tricky because it make take 2 different tests to know their true heartworm status.  The problem with cats is that you cannot treat them for heartworms if they already have them.  The medication (Immiticide)that is used to kill the adult worms in dogs is not tolerated well by cats and is dangerous to give. Cat's don't tolerate the death of an adult heartworm in their lungs very well.  This is why one of the most common symptoms of heartworms in a cat is sudden death. If a cat has heartworms, we will put them on a safe prevention to keep them from getting anymore worms.

So, we've talked about the mosquito, life cycle of heartworms, symptoms, testing, prevention.  Now we need to talk about what to do if a dog has adult heartworms.  There are a lot of variables that a veterinarian must consider when trying to give a pet owner a prognosis for their pet...size of pet, how many worms, does pet have symptoms, results of chest Xrays and bloodwork done on kidneys and liver. And no one can ever tell you that your pet will be OK.  You have to remember that this worm is big and can cause lots of damage. Treatment with Immiticide can run into the hundreds of dollars.

When the 12 inch worms die, they will be swept into the lungs like a thrombus or blood clot and can cause damage to the lungs. If the dog is a big dog and only has a few worms then he has a good prognosis. If it's a tiny dog with tiny lungs, then the pet has a worse prognosis because they can't handle the damage to the lungs as well as a big dog with big lungs. If the heartworm test shows a lot of worms, or if the pet is already showing symptoms of disease, then prognosis is worse.  The bottom line is that no one can promise you that the dog will be fine.

Many vets will put heartworm positive dogs on a particular once monthly prevention as soon as they are diagnosed with the worms. There are several reasons for this.  Prevention will keep the dog from getting more adult worms.  The owner of the pet may decide they don't want to have the pet treated with immiticide because of the risks or the costs.  You have to remember that the prevention will not kill the worms that the pet already has, but maybe the pet can live longer because it won't get more worms and maybe the pet will live longer than the worms. An average heartworm in a dog lives around 4 years. 

A heartworm that gets a dose of once monthly prevention may only live 2 years. If you don't treat with Immiticide to kill the adult worms, it's kind of like a game of Russian Roulette.  Who will live longer, the pet or the worm?
So my biggest recommendation? PREVENTION,PREVENTION,PREVENTION.  It's always better to prevent than to treat.  Preventative medicine is the way to go, it's cheaper and healthier for your pet.  And don't forget to give heartworm prevention every month, don't skip winter months, for the lifetime of your pet.  For more info, log onto www.veterinarypartner.com.

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