Heartworms In Humans: How To Identify

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Heartworms In Humans: How To Identify
Heartworms In Humans: How To Identify

Video: Heartworms In Humans: How To Identify

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Video: Why Don't Humans Get Heartworm? (Spoiler: We Do) 2023, February

It is well known that the favorite habitat of helminths is the intestines of humans or animals. However, there are extraintestinal worms that can parasitize in other organs of a person or animal: lungs, blood vessels, muscles, brain and heart. Helminths that parasitize the heart are called dirofilariae or, as they are popularly called, heartworms.



  1. What are dirofilariae
  2. Life cycle of heartworms
  3. How can you get heartworms?
  4. Diagnostics
  5. Symptoms of the disease
  6. Treating heartworms
  7. Complications of dirofilariasis
  8. Prevention of heartworms

What are dirofilariae

Dirofilariae are white filamentous worms that belong to the class of roundworms (nematodes). There are about 30 types of these worms, but two types are dangerous for humans:

  • Dirofilaria repens;
  • Dirofilaria immitis.

This type of worm does not lay eggs, they are viviparous parasites. The larvae develop in the uterus of the female dirofilaria and are then injected into the host's blood.

An adult female of the genus Dirofilaria repens reaches a length of 17 cm, and a male up to 7 cm. A female Dirofilaria immitis is 30 cm, and a male 19 cm. A female heartworm is capable of producing up to 30,000 larvae per day.

The species Dirofilaria ursi and Dirofilaria tenuis are capable of infecting humans, but do not go through the full development cycle in their bodies. They parasitize at the stage of microfilariae (immature stage of larvae of filariae of the genus Dirofilaria). Microfilariae cannot be detected with the naked eye, they are visible only under a microscope. Before maturation, the larvae are localized in the blood.

These worms infect the heart of cats and dogs, but can also be dangerous to humans. Sometimes dirofilariae are located in the eyes of humans or animals. All of the above parasites cause the rare disease dirofilariasis. The danger of this ailment is that the helminths parasitizing the heart develop very quickly.

Life cycle of heartworms

The final owners of dirofilariae are dogs and cats. Their bodies contain larvae, which, when bitten by a mosquito of the genus Culex or Anopheles, enter its body. Mosquitoes are intermediate hosts of dirofilariae; they become infected after being bitten by a sick animal. In the body of an insect, microfilariae go through two stages of development. The larvae (microfilariae) reach the gut of the mosquito after 24 hours. After another day they penetrate the vessels, and after about two weeks the larvae move into the body cavity of the mosquito and the lower lip. It is in this place that insects develop and become invasive for animals and humans.

When bitten by a mosquito, the larvae enter the blood of the final host. Within 3 months, they develop in the adipose tissue under the skin, as well as in the connective tissue, shed twice and grow vigorously. In the final host, the adults reproduce, producing microfilariae.


The larvae of worms of the genus Dirofilaria immitis penetrate into the pulmonary vessels and the heart, where they develop into adults. In the human body, dirofilariae develop for 7–8 months. Adult worms live in the body of a permanent host for up to 2 years. In the blood, the larvae are able to circulate for three years.

For Dirofilaria immitis, a person is most often a dead-end host, that is, the parasite accidentally enters his body and dies in it without the possibility of continuing its life cycle. For this reason, only the female parasitizes in the human body. However, it does not become a sexually mature individual. Also, worms, having entered the human body in the larval stage, cannot independently move, feed and reproduce. In order to parasitize the human heart, helminths must complete a developmental cycle in the body of an intermediate host. Dirofilaria repens is a frequent parasite of human subcutaneous tissue.

How can you get heartworms?

Dogs and cats are infected with these worms in a transmissible way, that is, the mechanism of infection transmission is carried out by the bites of a blood-sucking arthropod (insect or tick).


Mass infection of dogs occurs in the summer season, during the period of active life of mosquitoes. Most often, dogs are infected older than two years, less often up to one year. A person becomes infected with heartworms more often from dogs, less often from cats. Many patients are interested in the question: is dirofilariasis contagious? The infection is not transmitted from person to person. If one family member has been diagnosed with heartworms, then the rest can be calm, they are not in danger.

From the moment of infection to the moment of penetration of parasites into the human heart, it can take from several months to several years. The main danger is that at this time there are practically no symptoms of the disease.

Most often, heartworms are infected by people whose professional activities are associated with wild or domestic animals. The risk group includes:

  • hunters and fishermen;
  • pet owners;
  • trainers and dog handlers;
  • agricultural workers;
  • forestry workers.


To identify the disease, the following studies and tests are carried out:

  • electrocardiogram (ECG);
  • general blood analysis;
  • blood chemistry;
  • ultrasound examination (ultrasound);
  • serological and immunological tests (ELISA - test and others);
  • computed tomography (CT);
  • fluoroscopy and chest x-ray;
  • echocardiography of the heart;
  • magnetic resonance imaging (MRI).

The main research method is serological blood tests. Only microfilariae are found in the blood.

It is noteworthy that in a clinical study of blood in patients with dirofilaria, eosinophilia is not observed, as in other parasitic infections.

When conducting an ELISA test, antibodies to larvae can be identified in the blood of an infected person.

Sexually mature individuals are clearly visible during cardiac echocardiography. An electrocardiogram detects an increase in the right side of the heart (cor pulmonale).

With X-ray examination, ultrasound diagnostics and computed tomography, pictures can be obtained that indicate the localization of heartworms in the heart. This research method determines the prevalence of the pulmonary process and detects patients with a tendency to thromboembolism.

After diagnosing this ailment, it is necessary to urgently consult a doctor for treatment. Otherwise, complications may develop that can threaten a person's life.

Symptoms of the disease

Symptoms of heartworms are characterized by signs of heart failure. These include:

  • dyspnea;
  • cough;
  • pallor of the skin;
  • cyanosis of the mucous membranes;
  • tachycardia;
  • weight loss;
  • fast fatiguability;
  • hepatomegaly;
  • ascites;

When observing these symptoms in a patient, one can judge the far-advanced stage of the disease. Dirofilaria immitis is localized in the right ventricle of the heart and pulmonary artery. Parasitizing heartworms leads to the development of right ventricular hypertrophy. Further, this provokes right-sided heart failure. Since man is a dead-end host for the species Dirofilaria immitis, the result is the death of the parasite. However, when the parasite dies, it can block small branches of the pulmonary artery, which leads to a heart attack of the surrounding tissues. In addition, heartworms can cause thromboembolism.


When the parasites are located in the subcutaneous tissue, long non-healing ulcers, purulent wounds, itching and skin rashes can be observed. When such abscesses are opened, adult heartworms can be found. In the case of subcutaneous localization of the parasite, a characteristic feature is felt - the migration of the parasite under the skin throughout the body. In one day, the helminth is able to cover a distance of 18 centimeters.

Dirofilariae have their favorite locations under the skin. Most often they are localized under the skin in the following organs:

  • eyes;
  • face;
  • hands;
  • mammary gland;
  • neck and torso;
  • scrotum.

In half of the cases, dirofilariae are located in the eyes and the membranes surrounding them. A dense swelling forms under the skin of the eyelids. In this case, the conjunctiva, the anterior chamber of the eye, the sclera, tissues of the eye fossa and eyelids are affected. Patients constantly feel a foreign body in the eye, which interferes with quality vision.

When such infiltrates are found, cancer is primarily suspected, but when the tumor is excised, subcutaneous helminths are found.

A number of non-specific symptoms may also be observed:

  • nausea;
  • headache;
  • fever;
  • weakness;
  • pain at the location of the larva.

Treating heartworms

Treatment of dirofilariasis is a rather difficult matter, because in addition to destroying the parasites themselves and their larvae, the heart must also be treated. Patients with dirofilariasis go to the doctor at a late stage of the development of the disease, when the heart is seriously damaged. Therefore, the patient needs to visit two specialists: a cardiologist and a parasitologist. In order to destroy parasites in the heart, specific treatment is necessary.

If during the examination it was revealed that there is only one individual in the body, then there is no toxic effect on the body. In this case, treatment with anthelmintic drugs is not carried out.

If a parasitic worm of the genus Dirofilaria repens is identified in the body, surgical intervention is necessary. It involves removing nodes. Surgical treatment is combined with pharmacological treatment, in this case, a powerful therapeutic effect is achieved. If such steps are not taken, then the parasite can migrate to another organ. In order to prevent the migration of the parasite, the patient is prescribed a special drug that paralyzes the worm. His muscle activity is blocked and he is immobilized. When excising the worms, fibrous tissue is also removed.


Treatment of heartworms is carried out in two directions:

  • drug therapy;
  • surgical intervention.

Drug therapy is carried out using the following antihelminthic agents:

  • Ivermectin;
  • Mebendazole;
  • Dithiazanin;
  • Levamisole.

Along with surgery, the doctor prescribes the intake of supportive drugs that improve the patient's well-being:

  1. Sedatives. They are necessary to calm the heart and eliminate tachycardia. It can be not only pharmacological agents. In this capacity, you can use medicinal herbs.
  2. Antihistamines. They are used to relieve allergy symptoms.
  3. Anti-inflammatory drugs. These drugs are designed to eliminate the consequences of the destructive action of the parasite. For this, non-steroidal anti-inflammatory drugs are prescribed.
  4. Glucocorticosteroids, which have powerful anti-stress and anti-shock effects.

It must be remembered that the worms do not reach the heart immediately. It takes several months before they enter the heart. During this period, parasites migrate through the body for a long time. Their migration is asymptomatic, the person does not experience any painful sensations. However, someone who is used to listening carefully to their body may notice some alarming symptoms and seek immediate medical attention. Early diagnosis of dirofilariae will prevent their penetration into the cardiovascular system, and timely detection and destruction of parasites will not lead to surgery or the development of serious complications. Helminths that have already penetrated the heart are not excreted by any drugs. You can only get rid of them surgically. The operation to remove the heartworms is very difficult,and the rehabilitation period is very long.

Complications of dirofilariasis

Unfortunately, complications after dirofilariasis are not uncommon. The cause of complications lies in the fact that patients seek medical help late. According to statistics, 15% of all cases of dirofilariasis entail very formidable consequences. One of these consequences is allergic pneumonia. In this case, the patient is prescribed corticosteroids. As soon as the symptoms disappear, treatment is stopped immediately, since corticosteroids can inhibit the effect of anthelmintics.

Eosinophilic granulomatosis is also a serious complication. And in this case, the patient is also prescribed corticosteroids. Dead worms can provoke vascular embolism, which can lead to the death of the patient. To prevent this formidable complication, it is necessary to remove the parasite from the area of ​​the vessel by the endoscopic method.

Prevention of heartworms


Preventive measures are carried out in several directions:

  • extermination of mosquitoes;
  • prevention of human and animal contact with mosquitoes;
  • detecting cases of dirofilariasis in dogs and cats;
  • deworming of domestic animals;
  • catching and isolating stray dogs and cats;
  • treatment of the basements of residential buildings with insecticides, since the Culex mosquitoes can inhabit them all year round;
  • treatment of stagnant water bodies to reduce mosquito populations;
  • regular check-ups of pets by a veterinarian;
  • the use of screens for windows in houses;
  • using coils, tablets, and other mosquito repellents.

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