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Your Heartworm Questions Answered

Posted 11.07.12 by Katie Wooden, DVM

Welcome to The Pet Hospitals’ blog! We hope that this blog will give you some helpful information, as well as insight in to what we do as veterinarians every day.  We will be sharing some of our cases and discussing general topics as well, so stay tuned!

Very frequently, my clients ask me, “What do I need to do to keep my pet healthy?”. Besides giving them lots of love and attention and feeding them a well-balanced diet (with no people food in between),  one other topic is extremely important: preventing heartworms! Heartworms are rampant in this area and can have a serious affect on your pet’s health.

What are heartworms?

Heartworms are worms that can grow up to 14 inches long. As adults, they live in the heart, lungs, and pulmonary vessels.  Over time, these worms cause permanent heart and lung damage. Later, the heart may enlarge and become weakened due to an increased workload and congestive heart failure may occur. Heartworms can also cause blood clots that can lead to collapse and sudden death.  Once infected, heartworms can live in a dog for 5-7 years.

How do pets get heartworms?

Heartworms are transmitted from the bite of a mosquito that is infected with heartworm larvae.  The larvae enter through the wound and eventually enter the animal’s circulatory system. After maturing for two to three months, the worms enter the heart and lungs. Mosquitoes get infected with heartworm larvae by feeding on heartworm positive dogs or cats, as well as other animals, such as coyotes, foxes, wolves, wild cats, and ferrets.  It is not possible for heartworms to be transmitted from animal to animal, they are only transmitted by mosquito bites. Due to the high numbers of mosquitoes in our area, we are a very high risk area for heartworms.

Check out the Memphis area. Over 100 cases per clinic!

My dog only goes outside to go to the bathroom. Can he still get heartworms?

YES! It only takes seconds to be bitten by a mosquito infected with heartworms. Also, our homes are not safe from mosquitoes either. All pets should be kept on a heartworm preventative, regardless of their lifestyle or environment.

Can cats get heartworms?

YES! Cats are not as susceptible to heartworms as dogs, but it is estimated that 20-30% of cats are infected with heartworms. Cats typically have fewer worms than dogs, and the life span of worms is shorter, approximately two to three years, compared to five to seven years in dogs. However, the worms still produce serious heart and lung damage, leading to serious respiratory disease and occasionally sudden death.  Unfortunately, feline heartworm tests are not as accurate as canine tests, so false negatives are common. Also, there are currently no approved products for treating heartworm disease in cats. In order to keep your cat safe, the best thing to do is keep them on a heartworm preventative every 30 days. Talk to your veterinarian if your cat is not currently on a preventative.

How do I prevent my pet from getting heartworms?

While heartworm disease is treatable, it is much easier, safer, and cheaper to prevent it from happening! There are a variety of options for preventing heartworm infection in both dogs and cats, including monthly tablets and chewables, monthly topicals and a six-month injectable product available only for dogs. These medications interrupt heartworm development before adult worms reach the lungs and cause disease. These medications are safe and easy to administer. If given correctly and on schedule, these medications are extremely effective against heartworms. Talk to your veterinarian about the best heartworm preventative for your pet.

Do I need to give a heartworm preventative in the winter?

YES! The American Heartworm Society recommends year round treatment against heartworms .  Since our area tends to have mild winters, it is extremely important that your pets continue to receive heartworm preventative. Most of us have seen mosquitoes in our houses during the winter months, so heartworm transmission is still possible. Your pet should receive heartworm prevention every 30 days for life!

What are the signs of heartworms?

During the early stages of the disease, most dogs and cats will show no clinical signs. As the disease progresses, infected dogs may eventually show clinical signs, including a persistent cough, reluctance to move or exercise, fatigue after only moderate exercise, and a reduced appetite and weight loss. Severely affected dogs may have an enlarged abdomen and difficulty breathing.

Affected cats may be lethargic, have intermittent vomiting, exhibit coughing, or have difficulty breathing. Unfortunately, the most common clinical sign in infected cats is sudden death.

What if my pet gets heartworms?

While canine heartworm disease is treatable, it can be  expensive and rough on the patient. The goal of heartworm treatment is to kill the adult worms and also eliminate the baby worms (microfilaria). A product called Immiticide is the only treatment on the market approved to kill adult heartworms. This product is given as an injection in the muscles of a dog’s back. Due to the risk of blood clots from dying worms, dogs given this treatment must be placed under strict cage rest during treatment. Since Immiticide does not kill the younger heartworm larvae, treated dogs must start a heartworm preventative immediately. If your dog is diagnosed with heartworms, make sure to discuss all treatment options with your veterinarian.

There are still no approved treatment options for feline heartworm disease. If your cat tests positive for heartworms, please discuss your options with your veterinarian. We recommend keeping your cat on a flea/heartworm preventative every 30 days.


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