The W’s & H’s of Heartworm Disease | East El Paso Animal Hospital

The W’s & H’s of Heartworm Disease

WHY is Heartworm Disease affecting our pets?

In my opinion, heartworm disease is one of the least talked about conditions in veterinary medicine. Not only do I feel many pet owners are not aware of or have minimum knowledge of such disease, but veterinarians do not do a good job in making people aware of such serious disease during yearly check ups. Consequently, the prevalence of heartworm disease increases more and more every year.

Do you know what is scarier than having such a severe disease becoming more and more prevalent every year? The fact that such disease can be easily prevented, but it is not. Preventive medicine has advanced so much in the past years that all it requires now is a simple monthly treatment, a monthly topical solution or just one more poke from your local veterinarian. If I had to take a wild guess, I would say only about 20% of my clients have their pets in some type of heartworm preventative.


WHAT is Heartworm Disease? WHO does it affect? HOW does it affect your pet?

Heartworm disease is a parasite transmitted by a mosquito that likes to affect dogs, cats and ferrets. It is an extremely serious disease that can affect many organs, with the heart and lungs being more common. It can also affect kidneys, eyes, liver, blood vessels and your pet’s circulation/blood pressure. Heartworm disease can be fatal if caught late. If caught early, there is a chance for it to be treated, but can be pretty expensive (over $1000).

Common signs a pet owner might see early in the disease stage are a dry cough along with exercise intolerance and weight loss. As the disease progresses, your pet might start having extreme difficulty breathing and can develop congestive heart failure. Congestive heart failure caused by heartworm disease can also lead to liver disease and ascites, which is fluid accumulation inside your pet’s abdomen.

Cats usually present with mild signs of cough, vomiting, exercise intolerance and weight loss.


HOW does a Heartworm live?

Before talking about when and how to test for Heartworm disease, it is important to understand the life cycle of such evil parasite. Only then will we understand the reason behind the when and how.

It all starts when a mosquito bites a pet with circulating microfilariae, which are baby heartworms. The microfilariae get sucked in along with a blood meal and start maturing inside the mosquito for about 10-14 days. Then, the same mosquito bites a susceptible animal, depositing the microfilariae on the animals skin and creating a way through the bite for the worm to travel into its new host. Once inside a host, the microfilariae will swim around in your pets blood and eventually reach the heart and lungs. While traveling through your pets vasculature, it will take about 6 months to mature into full adults. This usually happens after the microfilariae have reached the heart and lungs. Once mature adults, heartworm tend to live about 5-7 years in dogs and 2-3 years in cats.


WHEN and HOW to test for Heartworm Disease?

Dogs: The common heartworm test used for dogs looks for the female adult heartworm. As stated above, it takes 6 months to have an adult heartworm. For this reason, we do not test for heartworm disease until your pet is about 6-7 months of age. It takes no more than 1 drop of blood and 10 minutes for us to test your dog. If your dog tested positive, we can confirm by placing another drop of blood under a microscope and looking for microfilariae or sending the blood to a lab to get tested by another means. If your dog tested negative, the next heartworm is performed within a year to make sure which ever preventative medicine you choose is effective and we make sure we catch the disease early enough in case it was not.

Cats: Heartworm disease is harder to detect in cats due to them having a higher chance of not developing adult worms. When they do, they can actually develop only male adults. For this reason, we test for antibodies, telling us your cat had exposure to heartworm if the test is positive. It requires 3 drops of blood and about 15 minutes for us to get results. Fortunately, this is the same test we use to look for FeLV/FIV infection, something recommended at least once a year and/or when a cat seems to be sick.

Ferrets: It is my understanding it is much harder to test for heartworm disease in ferrets compared to dogs and cats. We might recommend performing an antigen test and imaging. As I am not knowledgeable about ferrets, my best recommendation would be to ask your local exotic veterinarian.


WHAT types of preventatives are there to protect your pet?

There are 3 main ways to administer heartworm preventative: injectable, oral tablet or topical solution.

Injectable: In my opinion, this is by far the most common preventative I administer to my patients. The main reason is compliance. While the other methods are as effective, owners do have to remember every month to administer the prevention and hope their pets cooperate. With the injections, owners do not have to worry about the prevention until they have to come back for another injection. Pro heart 12 is the injectable that lasts for a year. My clients love to get this injection at the same time their pets get their annual check up, vaccines and heartworm testing. This way, their next visit to the veterinary clinic is usually not until a year later. Pro heart 6 is the injectable that lasts for 6 months. Price is the only reason to choose Pro heart 6 over Pro heart 12, as it does cost half the price for half the time of coverage. Unfortunately for cat owners, Pro heart injections are only labeled for dogs.

Oral tablet: While there are many tablet forms of heartworm preventative out there, I will only speak about Heartgard and Simparica Trio. If you are interested in another tablet form of preventative, please feel free to ask us. Heartgard has been available for years and is labeled to prevent both, heartworm and some intestinal parasites. Simparica Trio is a relatively new drug that is labeled to prevent heartworm, intestinal parasites, ticks and fleas. In order for both to be effective, owners need to make sure they feed the tablet as a treat every month. If you believe you can remember to do so and like giving your pet a treat, then this is your option. Heartgard is labeled for both dogs and cats. Simparica Trio comes only for dogs unfortunately.

Topical: While topical solutions are less common, they are still out there and available. The most common topical solution, specially for cats, is Revolution. Revolution prevents heartworms, some intestinal parasites, fleas and can even help with ear mites. While it is a great product, you need to make sure you administer it monthly by parting hair apart between shoulder blades and administering solution over skin. They have become the least common way of administration as not only do you need to remember to give it monthly, you also need to make sure you apply it accurately in a location that is not easy for your pet to lick off and make sure you do not bathe or mess with region for at least 24 hours after application.


WHAT if your pet tested positive?

If your pet tests positive for heartworm disease, your veterinarian will develop a long term plan of treatment. It takes several months to almost a year to be able to say heartworm treatment was successful. Treatment usually consists of monthly heartworm prevention, antibiotics and steroids at appropriate times, strict rest and visits to the veterinarian to give injections of a medication called Melarsomine directly in the muscle to help kill the adult heartworms. Your pet will be tested again after couple months, first by looking for microfilariae in a drop of blood under a microscope and then months later, running a heartworm test. It is really important to follow all the instructions your veterinarian tells you and mark your calendar with the important dates. Veterinarians can provide you with a schedule of what to expect during treatment.


WHERE is heartworm disease more prominent?

Areas where mosquitos are more willing to thrive are the most affected by Heartworm disease. This includes areas where it rains often or are close to watery bodies. According to the Heartworm Society, southeast United States is the most affected area.

That being said, El Paso is labeled as seeing 26-50 cases PER CLINIC per year. While that is not remotely close to the 100+ cases per clinic per year seen in areas in east Texas, it is 26-50 more cases than what we should be seeing in such a dry area.

If you have any questions about heartworm disease, testing or prevention, please feel free to ask us at any time. And please help us fight this severe but preventable disease. I know your pet would be more than appreciated to be heartworm free!


Written By: Dr. Carlos Dominguez


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