Monday, December 14, 2009

Heartworms in Dogs

Dog Heartworm: What it is and what you need to know
By: Shelley Vassall

While Heartworm disease in dogs is easily preventable [and treatable], it still continues to be a major problem. Heartworms are an internal parasite which live in the dogs blood vessels. They are transmitted by mosquitoes which means they can be found throughout the world. It is common for these worms to live in a dogs pulmonary arteries and the right ventricle of the heart. Whether your dog lives indoors or out (those living outdoors are four to five times more likely to be infected), every dog should be placed on a prevention heartworm program.
It is critical for dog owners to understand how the life cycle of the heartworm parasite works so as to be able to fully understand what to do to prevent and treat it.

How dogs get Heartworms

The infection starts when an a mosquito transmits (when biting the dog) an infected larvae. Once on the the dog, these infected larvae burrow under the dogs skin eventually developing into small worms. The entire process from bite to burrowing is one to 12 days. These larvae then remain under the dogs skin for 50-68 days before turning into worms. These worms then make their way through the dogs peripheral vein where they end up in the pulmonary arteries and the right ventricle of the heart. After approximately six months from the time the worms gained access to the dogs system, these small worms turn into adults. These adult worms can grow from 4 to 12 inches (10 to 30 cm) long and can live up to five years. In a dog that has been heavily infested, up to 250 worms can be found.

Depending on the number of worms living in an average sized dog, they will live primarily in the pulmonary arteries and the right ventricle of the heart (generally less than 50 worms). When the worm population increases to more than 75, they will then move to the right atrium (of the heart). If a dog has an even heavier infestation, the worms could migrate into the two large veins that carry blood to the right atrium of the heart. Heartworms can also eventually end up in a dogs lungs where they will cut off the blood flow and then cause the blood vessels to clot. By the same token, worms that wind themselves around a dogs heart valve can interfere with the overall mechanics of the heart; following this, the collapse and death of the dog can take place in just two to three days.

Heartworms Symptoms

Detection of heartworm in your dog is key to its treatment, depending on how long and how much the dog is infected. Dogs with few worms in their system, or a light infestation, may be asymptomatic. The signs themselves depend on both the size of the dog and the number of worms that have taken hold. Early, typical signs are: tiring easily, difficulty exercising (or not able to at all) and a soft, deep cough. Once the disease progresses, these signs become even more severe to where the dog will lose weight, their breathing will become more rapid and after exercising, they may faint.

Heartworm Diagnosis

Diagnosing heartworm is as simple as a blood test; the most accurate is called the Antigen test (this will identify the antigen produced by adult female heartworms). There are additional blood tests which are also used (whereby a sample of blood is used to identify parasites under a microscope), but the Antigen test is the most common and the one that is used most often. Following a blood test, if it becomes necessary, a chest X-ray is then used to determine the severity of the infection.

Heartworms Treatment

To treat heartworm disease, several factors must be considered: number of heartworms in the dog, location of the worms, medical complications, and age and condition of the dog. In layman's terms, a vet could decide to go after the adult worms first using a drug [intravenously] over a period of two days, that will poison them. Like with any drug, there can be side affects for the dog (loss of appetite, vomiting, vomiting, kidney failure and death). If these worms don't die, there are additional steps your vet will take with different drugs. If your dog is lucky enough to fall into a category where they can be treated, then three to five months following drug therapy, another Antigen blood test should be done; if all the worms were destroyed, the test will come back negative. If the test returns positive, you will need to consider re-treatment.


How To Prevent Heartworms

Ultimately, the treatment of heartworm disease is difficult and dangerous. Why put you and your dog through this ordeal when you can prevent it to begin with. Keeping your dog from being bitten by mosquitoes is the easiest way to prevent the disease, but it is also completely unrealistic. Dog owner's should talk to their vet about putting their dog on a heartworm prevention program. Administering of this easy to swallow chewable pill (or liquid applied to the skin of the dogs neck) should start at 6 to 8 weeks of age, particularly in areas where large mosquito infestations are prevalent. If you are not living in such a place, the heartworm pill (or liquid) should be given one month prior to the start of mosquito season and continue one month beyond the first frost (May or June to November or December). If mosquitoes are an issue all year long (such as in the Deep Southern U.S.), heartworm pills (or liquid) should be administered though the entire year.. In addition, any dog that is going to start on a heartworm prevention program, should have the Antigen blood test done first to ensure no heartworm is present. If you opt not to do this test prior to giving your dog the medication, your dog can become ill if heartworms are already living in the dog.

Make no mistake: heartworm disease is deadly to canines, but both you and your dog will be much better off if you just follow the simple prevention steps so as to avoid an outbreak altogether.

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