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Heartworm Disease in Dogs

Heartworm Disease in Dogs: All You Need To Know

Keep your pet healthy by doing checkups annually and keeping their vaccine records up to date. It helps keep off unwanted viruses and diseases, such as heartworms in dogs. 

Heartworm disease, also referred to as dirofilariasis, is a potentially fatal disease that affects pets. This disease is caused by blood-borne worm parasites called Dirofilaria immitis. These parasites are transmitted through mosquitoes, which carry their larvae. Once a dog is affected, the larvae mature into an adult and usually reside in the heart, pulmonary artery, and big blood vessels that can eventually cause severe lung disease, heart failure, and damage to other organs in the dog’s body. Heartworms can live up to 5 years inside a dog’s body and can produce offspring that live in the bloodstream.

Here’s a rundown on all you need to know about worms or heartworms in dogs, their symptoms, and how to prevent them.

How Is A Dog Tested For Heartworms?

The veterinarian will conduct blood tests to help detect the presence of worms in your dog. Since female heartworms usually release antigens, the test will look for heartworm proteins that contain them in the dog’s bloodstream. The antigen tests detect these infections when there are 1-2 female heartworms present, and the earliest these tests can detect the proteins in the blood will be 5 months after getting bitten by an infected mosquito. 

Aside from that, these tests also help detect microfilariae which help determine the infection of adult heartworms in a dog’s bloodstream. They can be checked through the test 6 months after the dog was bitten since larvae grow into full adults during this period. 

Another way of testing includes chest x-rays, which are recommended for dogs with heart diseases to check the extent of infection in the chest and lung area. 

When Should a Dog Be Tested for Heartworms?

Testing your dog for heartworms should be done annually and is usually done during the checkup and preventive maintenance care. If you have a puppy, they can get started on heartworm prevention for those aged 7 months and below. After the initial prevention, owners must schedule another checkup after 6 months, then another after 6 months, and after that, they can go back yearly to ensure their dogs are free from worms.

On the other hand, if you already have a dog that has no prior preventative measure for heartworms, a test for any possible worms must be done before they are given heartworm prevention. Similar to the puppy, they must return after 6 months and then schedule a routine checkup annually for worm-free maintenance. 

It has been proven that heartworm prevention medicines are effective; however, dogs can still get infected, so be sure to never miss out on the yearly preventative measures. Getting tested and keeping the prevention medicine up to date are great ways to avoid the risk of infection.  

Symptoms of Heartworm Disease in a Dog

Dogs will show no signs of having heartworms if their infection is recent or mild. However, once the heartworms mature as adults, they usually affect the lungs, and symptoms of heart disease must be checked. Check your dog if they cough, become lethargic, lack appetite, are easily tired after moderate exercise, and have difficulty breathing. 

The severity of the heartworm disease depends on how many worms they have, how long the worms have been residing in the body, and the changes in your dog’s behaviour to respond to the infection. Dogs that carry many worms and have had them for a long time usually show more obvious symptoms. 

There are four stages in checking for symptoms of heartworm disease in a dog:

STAGE 1: No symptoms or mild symptoms with occasional coughing

STAGE 2: Mild to moderate symptoms that include coughing and easily becoming fatigued after a moderate exercise.

STAGE 3: Severe signs include a sickly appearance, a persistent cough, and fatigue after light exercise.  Breathing difficulties and heart failure symptoms are frequent. 

STAGE 4: Possible development of caval syndrome wherein the blood flow to the heart is blocked due to many worms present. This is usually life-threatening and can be cured only through surgery, which is known to be risky, too. 

Treatment for Heartworm Disease in Dogs

If your dog’s tests come out positive for heartworm disease, treatment is available to remove the disease and cure your dog. Once the vet confirms the diagnosis, they will need to prep the dog since the treatment is known to be expensive and complicated. They will need to stabilise your dog’s condition in preparation for therapy to heal them. Depending on the severity of your dog’s disease, the process and treatment will vary.

A drug that is developed to kill larvae and adult heartworms will be administered by the veterinarian. The treatment drug will be given in doses appropriate to get rid of the parasites. During this time, your dog will need to rest and be hospitalized to monitor their condition. Additional medications are also given to dogs depending on their response to the drug, which can help stabilise their condition and prevent inflammation. 

Prevention For Dogs To Get The Heartworm Disease 

Yes, heartworms can be prevented! It starts with consistently taking your dog to their annual routine checkups to get their dose of preventative measures for heartworm diseases. Your vet will recommend the best way to prevent them, and you must always renew it yearly. 

If your dog has no prior preventative measures, testing is a must before the heartworm prevention is given. Checkup after 6 months must be done before their next dosage, a year after their last routine visit. Have your pet regularly tested for early detection and prevention. 


Heartworm disease in dogs is a potentially fatal disease caused by a bite from an infected mosquito that carries the parasitic larvae. No symptoms are present as the larvae grow, but when they mature, adult heartworms can produce offspring and multiply. Adult heartworms can affect your dog’s lungs, heart, bloodstream, and other organs of the body. That being said, the best way to prevent heartworms and illnesses that are life-threatening is to get your dog tested. After testing, preventative measures are taken by your veterinarian if the results are negative. 

Maintain your heartworm prevention for your pet annually to effectively prevent heartworm diseases. On the other hand, if your dog starts to show symptoms such as coughing, lethargy, and a lack of appetite, bring them to the vet for testing. If they become positive for heartworms, treatment is available to help get rid of heartworms. Prevention is key to avoiding heartworm diseases that can lead to fatal conditions and keeping your dog healthy. 

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