Heartworms In Dogs: What You Should Know

Heartworms in dogs: What you should know

Heartworms In Dogs: What You Should Know


Heartworm disease or what is called (Dirofilariasis) is a serious and sometimes fatal disease in dogs. This disease is caused by a blood-borne parasite known as Dirofilaria immitis.

From asymptomatic cases to severe cases, veterinarians face many challenges from recognizing and diagnosing the disease to successfully completing a treatment plan. But the first step to overcoming this disease is to understand it well and know how it is transmitted.

Here’s this article from Meduo about heartworms in dogs and what you should know about them.

Life cycle of the heartworm (D. immitis)

Infection begins when a mosquito bites a heartworm-infected dog, when blood containing immature heartworm larvae (L1) is transmitted to the mosquito. The larvae of the worm begin to mature inside the mosquito until they reach the stage (L3), which migrate to the oral parts of the mosquito; In preparation for the next host infection.

When the infected mosquito bites the next host (we’ll assume it’s the dog); The larvae migrate through the subcutaneous tissues to the bloodstream, and then migrate through the tissues of the body until they reach their preferred sites as mature heartworms, which are the pulmonary and heart blood vessels, to complete their development and begin to reproduce there.

Life cycle of the heartworm

Then, the mature female heartworm produces microfilariae. This life cycle lasts 6 to 7 months, during which time the host dog is largely unaffected by the larvae.

Problems begin to appear in the host dog when heartworms mature into adulthood, which reside within the major blood vessels of the heart and lungs, primarily within the pulmonary artery. These adult worms obstruct blood flow through the heart and lungs.dog life expectancy after heartworm treatment

Diagnosing heartworms in dogs
Clinical signs
It can take years after infection before clinical signs of heartworm disease appear in dogs. Early clinical signs of the disease include; Continuous soft cough, unwillingness to exercise, fatigue after any moderate exertion, decreased appetite, in addition to weight loss.

As the disease progresses and becomes more severe, congestive heart failure may occur on the right side (Right sided congestive heart failure); Where the heart works harder to pump blood in the presence of worms that live and multiply in the blood vessels, and as a result; Fluid builds up in the abdomen, causing ascites

Blood vessels may suddenly become blocked due to the presence of large numbers of worms, leading to a condition called Caval Syndrome, which requires emergency treatment.

Antigen tests

The antigen test detects the antigens present in the reproductive tract of the adult female worm. This protein cannot be detected until the worm larvae (L3) mature to adulthood, therefore; Since circulating antigens will not be detected 6.5 to 7 months after infection; The antigen test in puppies younger than 7 months is not effective.

For dogs old enough to be tested, the antigen test is less effective if the infection is old (and the worms are no longer reproducing), or if most of the worms are male and there are few females (less than 3 adult female worms).

You can improve the diagnosis by heat treating the sample before the test. Although this procedure is not always used, it can be useful when heartworm disease is highly suspected, but the first antigen test is negative. Heat treatment denatures the so-called circulating immune complex proteins resulting from the binding of antibodies to heartworm antigens, causing the precipitation of antibodies and liberating the antigen, thus facilitating its detection.


There are some risks involved with heartworm treatment in dogs, although fatalities are rare.

In the past, medication used to treat heartworms in dogs contained high levels of arsenic and frequently caused side effects. But now a new drug is available that does not have many side effects, providing a successful treatment for more than 95% of dogs infected with heartworms.

Complete rest is essential after treatment

The adult worms die within a few days of treatment and begin to decompose. When the worms decompose, they are carried to the lungs where they lodge in small blood vessels and are finally absorbed by the body.

It can take several weeks to months for dead worms to be sucked out, and most post-treatment complications are caused by dead heartworm fragments.

This period can be dangerous, so it is absolutely essential that the dog stays as quiet as possible for up to 6 months, and is not allowed to play or exercise for a month after the final heartworm injection.

The first week after injection is critical, as this is when the worms die.

Prevention of heartworms in dogs

There are three forms of effective heartworm preventative medication, available by mouth, topical, or by injection.https://furkids.org/how-we-help/lifesaving-programs/heartworm-treatment-program

These preventatives work by killing heartworm (L3) larvae and stopping them from developing. Because these larvae grow so rapidly, the interval between doses is usually every 30 days for oral and topical medications, and every 6 months for injections.

Prevention protocols must start early; When does the dog reach 8 weeks of age? Before the dog receives the preventive medicine, the American Heartworm Association recommends that it be tested to ensure that it is negative. As for small puppies that have not reached 7 months, this test is not required before giving preventive medicines.

An annual test is recommended to make sure your dog does not have a heartworm infection. Because no drug is 100% effective, and you, as a veterinarian, cannot guarantee that the dog owner will comply with your instructions 100%.

Convalescence phase after treatment

When heartworm disease is detected in dogs, the dog should not perform any activities after recovering from the disease for at least 8 weeks.

You may need to put the dog in an iron cage if you take care of the dog in your home, because the intense movement may lead to serious complications for your dog’s health.

Anthelmintic antibody analyzes are performed monthly for four months after recovery to ensure that there are no remnants of Dirofilaria (heartworm larvae) in the blood.

In the event of a recurrence of the injury, the veterinarian decides the feasibility of repeating the treatment or performing a surgical intervention.

For heartworms in dogs

In order to treat heartworms in dogs, the attending physician gives special medical preparations to help kill the adult form of heartworms so that the dog can improve and recover easily.

At this stage, it is preferable to place the dog in a therapeutic host so that it is monitored periodically by specialists.

After eliminating the large worms and making sure that they are completely gone through x-rays and tests, the doctor deals with Dirofilaria “worm larvae”, which takes some time in treatment.

The doctor gives a monthly treatment to prevent and kill any larvae formed in the blood and prevent their growth to form large worms again. At this point, the dog can be treated at home.

Heartworm prevention

If heartworm infection appears in any geographical area, all dogs must take preventive measures and be vaccinated so that the disease is not transmitted to them.

Therefore, you can ask your veterinarian about the appearance of this infection in your geographical area, and consult him about the appropriate prevention from it.

You should also conduct a periodic examination annually or once every six months to prevent your pet from any possible diseases. Regular examination will always help you to predict diseases and confront them early before they worsen


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