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What Pet Owners Need To Know About Heartworms

Most dog owners have heard about heartworms, but many do not fully understand the extent or significance of the disease. Unfortunately, heartworms are far too common, affecting approximately one in every 200 dogs annually. If owners are not aware of some important aspects of the disease, they cannot take correct preventative or treatment measures to help their pets.

The worms can fester and reproduce inside the dog for years resulting in worms clogging major blood vessels, making their way to the lungs, and ultimately the heart. Their presence is not limited to dogs, as it can affect a host of other animals, and in some rare cases even humans. Dogs are natural hosts for these parasites, however, meaning they can carry them in their systems for years, while the worms grow and mature, at which point they begin to do real damage to various organs.

To be ready, it is important to understand how heartworms are transmitted, how to look for signs of heartworms, what is involved in testing for heartworms, and if the heartworms are treatable. Here are a few relevant facts pet owners should know.

How Do Animals Get Infected With Heartworms?

Wild animals like foxes, coyotes, wolves, and other mammal species in the wild are typical carriers of these worms. The infection process occurs when a mosquito bites an infected animal who has the eggs of heartworms (called microfilaria) laid by a female worm, ingesting them. For about 2 weeks, these worms mature to larvae, at which point they become infectious.

The mosquito then carries the baby worms and bites the unlucky dog, cat, or other domesticated animals, leaving the larva on their skin. The worms quickly make their way in through the mosquito bite, infecting the animal’s blood. After 6 months, the worms mature enough to reproduce and begin to spread through the animal’s bloodstream and into their organs causing potentially fatal aftereffects.

The worms can survive as long as 7 years in a dog and up to 3 years in a cat. Considering that multiple mosquito bites can occur per season with the same effect, and mosquito bites can happen every year, the number of heartworms that spread can be very significant.

What Are Signs Of Heartworm Disease In Dogs?

Signs of heartworms can vary from one dog to another. Some dogs can go for a long time showing no symptoms, especially early in the stages of the infection. Those dogs who have preexisting health conditions or are heavily infected, start showing signs of the disease earlier.

Some of the signs include reduced appetite, fatigue, lethargy, weight loss, and a mild cough if the worms have reached the lungs. Another sign to look out for is a swollen belly because dogs retain excess fluid. When there is a large number of worms, they invade the essential blood vessels, blocking flow to the heart. If the dog begins to experience labored breathing, has dark red or brown urine, and shows pale gums, the infection might already be excessive and the dog needs emergency surgery.

How Does Heartworm Testing For Dogs Work?

Testing for heartworms for dogs should be performed annually and is typically done during a routine vet visit. It is important to keep in mind that it takes up to 6 months after the initial visit to get positive test results after the infection. Young puppies who are under 7 months old can start preventative measures without a heartworm test, but testing should happen 6 months after their initial visit. Adult dogs require testing before preventative measures are started. If the dog is diagnosed, it needs to be checked every 6 months to make sure the prevention is working.

This is done in an effort to detect heartworms as early as possible and begin treatment. Medications can be prescribed if a dog tests positive, and the medications are potent and effective. However, they are not going to stop reinfection, so it is important not to miss any medication doses when the treatment plan is in place. This is also true if the dog throws the medicine up. 

If a dog tests positive during an antigen test, the diagnosis is confirmed with a separate test. This is to be sure that the initial test is not a false positive because the treatment plan for heartworm can be costly and complicated, so it's important to be sure.

Are Heartworms Treatable?

As noted earlier, heartworm medicine is very effective, but it is not 100% guaranteed for all dogs. If a dog is infected with heartworms, early detection increases the chances of a full recovery exponentially. Once the dog begins to show signs of the disease, it is important for the treatment to first stabilize the dog’s system by killing off the adult worms without excessive side effects during the treatment process.

One of the hardest things to address is keeping the dog somewhat docile, especially if the dog is typically very active. However, once the diagnosis is confirmed, the dog’s physical activities should be restricted to reduce the exertion on the heart which the heartworms may have damaged. This will then be followed by therapy to stabilize the dog’s condition. Once that has been accomplished, the medical treatment can begin.

The vet will outline a treatment plan in a set of detailed steps following the American Heartworm Society guidelines. The further along the heartworm disease, the more risk of complications exist as the worms spread throughout the organs. The tricky thing is that the infection could be much farther along than what the symptoms indicate, especially in otherwise healthy animals. This means that continuous testing (about 9 months after the treatment especially) is used to assure that the condition improves.

Dog’s can always get re-infected, so many vets advise dog owners whose pets have had severe cases of heartworm, but recovered, to continue heartworm medicine for the rest of the dog's life as reinfection could prove fatal.