How Dogs Get Heartworms : Reason, Prevention & Treatment

how dogs get heartworm

From exploring the world to socializing, dogs do almost everything with their mouth. They lick to groom themselves, or slurp to show affection, they sniff to browse info, and they gobble anything in their path, including dust, dirt, trash and poop. Hence, they are bound to pick up pests, and become ideal hosts to a variety of worms and parasites. However, not all parasites that affect a dog enter through its mouth. Some parasites have carriers that transmit deadly diseases to your dog. One such deadly invader is the Heartworm. Let’s learn the facts about heartworms and how dogs get heartworms so you can keep your dog healthy and heartworm-free.

Parasites and de-wormers

Parasites worm their way into most dogs’ lives at one time or another. But, before we can know about what heartworms are, we need to talk about the two types of parasites (worms) which your dogs might have to fight against.

First kind, the ones that live in the intestines, namely – tapeworms, roundworms, hookworms, and whipworms. These worms enter your dog’s stomach and make merry in the gut. You may suspect worms if your dog shows symptoms like vomiting, diarrhea, coughing and shortness of breath, weight loss, or licking under the tail. However, they can be gotten rid of using de-wormers. Your vet will start a precise routine to de-worm your dog since puppyhood. Such worms can be managed by showing them the way out.

Heartworms are another type of parasite, and they can be far more deadly for your dog, even while being treated with medicine. Prevention is the best medicine for heartworms. More importantly, the regular broad-spectrum de-wormer tablet/shot your vet gives your dog does not control or kill heartworms, and one needs a separate treatment for dogs infected with heartworms. Though various treatments are available, prevention is the wisest approach to dealing with heartworms.

What is a heartworm?

how dogs get heartworms

Dirofilaria immitis, commonly known as heartworm, is one of the most dangerous types of parasites that can cause serious health issues in your dog, or sometimes even death.  A dog heartworm is a small thread-like worm, which grows to a foot-long and lives in the heart, lungs, and blood vessels of an infected dog. Adult heartworms dwell in the lung arteries, and damage the lung vessels and tissues.

Additionally, in cases of advanced worm infestation, adult heartworms may migrate to the right side of the heart. Heartworms cause dirofilariasis (heartworm disease) in dogs, which when left untreated, eventually leads to death, most often as a result of secondary congestive heart failure.

How dogs get heartworms ?

Unlike many other parasites, heartworms do not spread from dog to dog, but it requires an agent, the mosquito, to infect new hosts. Heartworms spread only through the bites of mosquitoes. A mosquito picks up immature heartworms (about a 1/100th of an inch in size) while it is taking a blood meal. These immature worms, called microfilaria, are the larva of the heartworms circulating in the bloodstream of infected dogs. The mouthpiece of the mosquito then carries this microfilaria from an infected dog to an uninfected one. The young worms immediately travel through the bloodstream of the dog, and after about two-three months, settle in the right side of the heart, where they begin to grow.

Heartworms go through several life stages before they become adults infecting the heart of the dog. Once a dog is bitten by an infected mosquito, it takes about seven months for the immature worms (larva) to mature into adult heartworms. They gradually circulate through the blood and reside in the heart, lungs, and surrounding blood vessels, and begin reproducing. An adult heartworm can grow up to 10-12 inches in length, and can live for 5-7 years. A severely infected dog can have as many as 250 worms in its system.

Signs of heartworms in dogs

If your dog has parasites like tapeworms, hookworms, or whipworms in his intestines, he will probably show symptoms more or less like- itchiness around anal area, licking around the anal area, eating well but no weight gain, poor skin condition, dull coat, anemia, diarrhea, vomiting, etc.

In the case of heartworms, since an infected mosquito is the bug that carries the heartworm parasite to your dog through biting, your dog will likely and sadly suffer from the following symptoms:

  • A mild persistent cough
  • Reluctance to exercise or play
  • Fatigue after moderate activity
  • Decreased appetite
  • Weight loss

As the heartworm infection turn into a heartworm disease, dogs may develop a swollen belly due to excess fluid in the abdomen. Dogs that have a large number of heartworms, or even as less as 15 adult heartworms in the case of miniature dogs, can develop a sudden blockage of blood flow within the heart leading to a heart-failure. This is marked by rapid laboured breathing, pale gums, and dark bloody urine. Without prompt diagnosis and quick surgical removal of the heartworm blockage, very few dogs survive.

When should a dog be tested ?

Heartworm disease is a progressive disease. The earlier a disease is detected, the better the chances of cure and living. With prompt intervention at the early signs of disease when a dog is infected with heartworms, it is important to get a heartworm test done by a vet. The heartworm test requires just a small blood sample from your dog, and it works by detecting the presence of heartworm proteins.  

Testing procedures and timing vary for dogs depending on their age group. Having said that, all dogs must be tested annually for heartworm infection. I usually do this during a routine visit to the vet as a preventive care for my dogs. The following guidelines are recommended for timing and procedure of heartworm testing:

Puppies: Dear owners, please note that, it takes at least 6 months for a dog to test positive after it has been infected. Hence, for a puppy under 7 months of age, you can start a heartworm prevention care regime without a heartworm test. Make sure, your puppy is tested 6 months after your initial visit, tested again 6 months later, and once in every year after that to ensure he is heartworm-free.

Adult dogs: If your dog is over 7 months of age and has not been tested even once as a preventive need, then he needs to be tested prior to starting a heartworm prevention care. Likewise, he too needs to be tested 6 months later, and 12 months later and yearly after that.

In case of one or more missed doses, the dog should be tested immediately, then tested again six months later and annually after that. Heartworm medications are very successful, but dogs can still become infected. Hence, annual testing is necessary even when your dog is on a heartworm prevention care year-round to ensure that the prevention program is working.

Note: It takes at least 6 months for a dog to test positive after it has been infected.

Preventive measures for heartworm disease

  • Test for heartworms. You can’t give your dog preventative medication if he is already infected with heartworms. If you do so, it will cause series health complications in your dog.
  • After testing, when the test results are found to be ‘negative’, you can start giving your dog his vet recommended dose of preventative heartworm pills or shots. Do keep a record for the same in your dog’s health book.
  • There are medications available for heartworms as a once-a-month chewable, and a twice-a-year injection shot. You can discuss with the vet and choose the best option for your dog.
  • To be on the safe side, get a heartworm test done once in a year with the vet’s guidance.
  • Do not give your dog OTC or non-prescribed pills.

Heartworm disease treatment & care

If your dog tests positive for heartworms, do not worry, the good news is, most infected dogs can be successfully treated. Your initial goal must be to stabilize your dog when he shows signs of heartworm infection, and secondly, to kill all the adult and immature heartworms. Basically, the heartworm treatment has these steps:

  • Confirm the diagnosis because the treatment for heartworm is both expensive and complex, and you will want to be absolutely sure that treatment is necessary.
  • Before you begin the actual heartworm treatment, you may need to stabilize your dog’s condition with appropriate medication therapy. In extreme cases of heartworm disease, or when a dog has another health condition, the process can take several months.
  • Once the vet has stabilized your dog, he will start the heartworm treatment involving several steps. Usually, dogs with mild signs or no signs of heartworm disease are more likely to have an effective treatment. More severe disease can also be successfully treated, but the risk of complications is more.
  • Approximately 6 months after the completion of the treatment, the vet will do a heartworm test to confirm that all heartworms in the dog have been eliminated. To avoid re-infection, it is wise to administer heartworm prevention yearly for the rest of his life.
  • Restrict your dog’s exercise and play, and make sure he gets plenty of rest even after the treatment. This is because, when heartworms die they break into pieces, and these pieces can block blood from flowing to the heart or lungs. When that happens, there is a greater chance when blood pumps harder, such as during exercise or running, a dog could die. Ask your vet for tips to make sure your sick dog gets rest so he can recover safely.

Why are heartworms such a big deal ?

Currently, there is no vaccine available for the prevention of heartworm disease in dogs. However, research scientists are working on this. At this time, heartworm disease can only be prevented through the regular and appropriate use of preventive medications prescribed by veterinarian. Heartworms in dogs are easy to prevent, but difficult and costly to cure. Moreover, mosquitoes are everywhere, and there’s no way to tell if a mosquito is infected. That’s why prevention is so important. If you have mosquitoes and you have dogs, you’re going to have heartworms. It’s just that simple.

Share this very interesting and informative article with all dog dog parents out there.

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