Some people feel it is safe to stop their pets (dog and cat) monthly heartworm preventative medicine in the fall and winter. This is not a good idea. Heartworms are transmitted by mosquitoes. The mosquito will bite an infected animal and ingest the heartworm microfilaria. It only takes 10-14 days for the larvae to develop. At that point if the mosquito bites an unaffected animal, it will transmit the larvae to that animal. What makes heartworm risky is that they can live in a dog for up to seven years and a cat for three.

Heartworm is a dangerous condition that can cause severe lung disease, heart failure and damage other organs in the host’s body.

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At one-time heartworm was found only in the warmer states, but now it has been detected in all states. The warmer wetter environments that support mosquitoes have the most risk.

The symptoms for dogs include a mild but constant cough, a decrease in activity, fatigue, loss of appetite and weight loss.

Fortunately the medications for treating heartworms have become safer. They are an arsenic-based product called Immiticide. Before treating a dog for heartworm, it is necessary to do a thorough pre-treatment program. This will include x-rays, blood work and perhaps other tests to determine how much damage has been done to the dog’s organs. This way the veterinarian will know what to expect and what to look for which will help with the post-treatment care of the dog.

The post-treatment care is critical in saving the dog’s life. Although the treatment will kill the adult heartworms, their bodies will break up and the pieces can block the pulmonary vessels and/or lodge in the lungs. This is why a dog that has been treated for heartworm must be kept quiet for months after the treatment. This is also why pre-treatment tests can be critical for the dog’s survival.

Unfortunately there is no approved treatment for treating heartworm in cats. Some veterinarians have used a drug approved for dogs on cats, but with major side effects which include sudden lung failure and death. The other risk in treating cats is that they are more likely to die from a reaction to the dead pieces of heartworm in their heart and lungs.

One of the choices is to treat the symptoms from heartworm and hope that the cat outlives the worms. Heartworms only live in a cat for two or three years.

If a cat is treated for heartworms, it will need veterinarian supervision for several months. Often, they need oxygen, cortisone and sometimes a diuretic to remove fluid from the lungs. When they are stable, cats will continue to need corticosteroids either continuously or periodically. There is always a risk of sudden death.

The good news is that in some parts of Europe and Japan, veterinarians have been surgically removing the heartworms, however, the technique has yet to be improved and approved.

In the case of both dogs and cats, prevention is the better way to go. This is easily done with monthly heartworm preventative medicine for both dogs and cats.

Because heartworms can live in a dog or a cat for years, it is imperative that the pet be tested first before giving heartworm medicine. By giving the pet a monthly preventative year-round, you are doing the best you can to avoid these deadly worms.