Dog Heartworm - The Silent Killer

Dog heartworm is a silent killer.  This is because the heartworm is insidious andÍ once your dog has been infected; it can take months or even several years before it shows symptoms of heartworm.  In fact, your dog may show no signs of this infection until the heartworms mature.  And the diagnostic checks currently available cannot detect the presence of the young heartworms called microfilariae before they mature.

What Is Dog Heartworm?

Heartworm is an internal parasites that live and breed primarily in the heart and pulmonary (lung) blood vessels of infected dogs.  It is a disease that is common in dogs throughout most of the United States.

Heartworm is caused by a roundworm that belongs in a family of Filariidae.  A female heartworm can measure from nine to 16 inches in length.  A male heartworm is little more than half this size and is characterized by corkscrew turns of their posterior that are often referred to as their “pigtails.”

Heartworms live within the chambers of the dogs and usually extend through the valves, seriously impairing the heart’s operation.  In heavy infestations, the worms migrate up the pulmonary artery and clog the blood vessels of the lungs.  This causes the loss of body weight, chronic cough, shortness of breath, dropsy, muscular weakness, vision problems, chronic heart failure and, eventually, death.

What Causes Heartworm In Dogs

Heartworm begins when a mosquitoe that has fed on an infected animal bites your dog.  When the mosquitoe bites the dog, it deposits infected worm larvae into the dog’s skin.  These small heartworms burrow into the dog and lodge in the dog’s tissue where they remain for several months.

As they get bigger, the worms leave the tissue and enter the dog’s blood stream through the wall of a small vein.  They will then travel through the dog’s blood stream and eventually lodge in the chambers on the right side of the dog’s heart where they develop into mature heartworm.

Diagnosing Heartworm In Dogs

Only a veterinarian can diagnose heartworm as the symptoms of this disease vary considerably.  The bad news is that many dogs show no visible symptoms of this disease until it has progressed to the point where it is no longer possible to treat.

All dogs with adult heartworms should show micro filarial activity, which can be detected via a blood test made by a veterinarian.  Since these microfilariae usually appear within nine months after an infection, it is possible to detect and treat the worms when the disease is still mild and not life threatening.

Symptoms Of Dog Heartworm

Unfortunately, dog heartworm symptoms rarely can be seen until the disease has reached an advanced stage.  When this occurs, the dog may suffer congestive heart failure, coughing, loss of energy, dull coat, difficulty breathing, and maybe fainting spells and an enlarged abdomen.

Treatment For Dog Heartworm

The first step in treating heartworm in dogs is for the vet to evaluate the dog and treat any secondary problems such as heart failure or liver or kidney problems.  This is to make sure the dog can withstand the treatment.  Next, the vet will most likely treat the dog with an arsenic-containing drug that is given by injection deep into the muscles of the dog’s lower back.  This treatment is usually given in two doses each day for two days, followed by inactivity to give the dog’s system time to absorb the dead heartworms.

Following this, the dog may be given further treatment to kill the heartworm microfilariae.  In this case, the dog is dosed daily for a week and then given another blood test.  If this test shows that heartworm microfilariae are still present in the dog, the dose can then be increased.

If the heartworm disease is very advanced, the vet may suggest – as an alternative – removing the adult heartworms surgically.

Preventing Heartworm In Dogs

The best way to combat dog heartworm is to make sure your dog has regular checkups and that they include the blood test for heartworm microfilariae.

However, if you live in an area with mild winters, your vet may suggest a year-round program of heartworm prevention.  For example, he or she can prescribe a drug now available in tablet form that provides protection for one month.  However, the use of these preventative medications does not mean you should not make sure your dog has periodic blood tests.

Regular blood tests for heartworm microfilariae combined with the use of heartworm preventative medications have saved the lives of many dogs.

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