Microfilariae in the human body are signs of their presence. Dirofilariasis in humans: symptoms and treatment

A person becomes infected with dirofilariasis when bitten by an infected mosquito of the genus Culex, Aedes, Anopheles. The final owners of dirofilaria are animals of the canine, feline, and viverrid families. In an infected animal, microfilariae circulate in the blood, which are not contagious to humans or other animals. During a mosquito bite of a sick animal, the insect becomes infected. And already in the body of a mosquito, microfilariae turn into an infective larva. Then the infected insect bites a person and thereby infects him with dirofilariae. The larva grows in the tissues of the human body, but does not turn into a sexually mature individual. Therefore, it remains unable to reproduce in the human body.

Often, when infected, one larva enters the human body, less often two, even more rarely two or four.

Symptoms of the disease

Dirofilaria repens and Dirofilaria immitis cause different forms of the disease. The first is the cause of subcutaneous dirofilariasis, the second is visceral. On the territory of the post-Soviet countries, it is subcutaneous dirofilariasis that occurs. And the visceral form is typical for countries such as Japan, the USA, Canada, Australia, and Southern Europe.

Symptoms of subcutaneous dirofilariasis

The incubation period lasts from a month to a year. The first symptom of the disease can be considered the appearance of a tumor-like formation under the skin or mucous membrane, which is accompanied by redness, itching in this part of the body. The formation itself may be painful or not bring any discomfort. A characteristic sign of the disease is the migration of the helminth, which is noted outwardly as the movement of the formation through the body. In two days, the larva is able to cover a distance of thirty centimeters.

Often, having found a tumor-like formation on the body, people go to the surgeon, who suggests a diagnosis, fibromas, atheromas, etc. But during the operation, the doctor discovers an unexpected find in the form of a helminth.

Dirofilaria have their own "favorite" places in the human body. These are such parts of the body (as the frequency of the lesion decreases):

Also, with dirofilariasis, nonspecific symptoms are also observed in the form of weakness, fever, pain in the area where the larva is located, which can radiate along the nerve fibers.

Approximately half of the cases of dirofilaria are localized in the eyes and their surrounding membranes. The eyelids, conjunctiva, anterior chamber of the eye, sclera, tissues of the eye fossa are affected.

In such patients, there may be a sensation of a foreign body in the eye, redness of the skin of the eyelids, ptosis, blepharospasm. A tumor forms under the skin.

When the conjunctiva is affected, severe pain, lacrimation and itching are noted, caused by the movement of the helminth. The conjunctiva is hyperemic at the same time, through it it is sometimes possible to view the helminth itself.

In many patients, dirofilariasis manifests itself as a relapsing course with periods of exacerbation and extinction of the disease. With untimely extraction of the helminth, inflammation in the soft tissues may develop, as well as the formation of an abscess.

This form of dirofilariasis is often asymptomatic. Sometimes patients may experience chest pain, cough, hemoptysis.

The disease is detected in most cases suddenly during a chest X-ray or even during lung surgery if a malignant process is suspected. On x-rays in the lungs, nodules with a diameter of 1-2 cm are determined.

Diagnostics

An auxiliary diagnostic method can be attributed. With dirofilariasis in the blood of a person, antibodies to migratory larvae (toxocar) can be detected. A positive ELISA result cannot be the only correct one for determining the final diagnosis.

In addition, methods and can be used at the preoperative stage. On the obtained images, it is possible to detect a small formation of an oval or spindle-shaped shape.

It is noteworthy that eosinophilia in the clinical blood test in dirofilariasis is not typical and is observed only in 10% of all cases.

Treatment

In cases where dirofilaria constantly migrates, it is difficult to catch it, but there is a threat of damage to the organ of vision, preparations containing albendazole (vormil, medizol) may be prescribed.

According to the indications, desensitizing therapy is carried out.

Prevention

When conducting screening activities, it was found that in different regions of Russia, approximately 4-30% of dogs are infected with microfilariae. While in Greece and Iran this figure reaches 25-60%. It is noteworthy that the intensity of human invasion depends on the season. Dirofilariasis in humans is recorded throughout the year, but in most cases it develops in the spring-summer period and less in autumn-winter, which is probably due to an exacerbation of dirofilariasis in dogs.

Prevention of the disease consists of three areas:

Mosquito control;
Identification of dirofilaria in dogs with subsequent treatment;
Prevent human and animal contact with mosquitoes.

Mosquito control

It is known that foci of dirofilariasis are formed near water bodies near settlements. Here, state and medical structures carry out measures to combat insects.

In addition, in the basements of multi-storey buildings, Culex mosquitoes can live almost all year round. Insects penetrate the ventilation system into apartments, where they bite people, as well as animals. Therefore, appropriate measures should be carried out in the basement of houses.

Diagnosis of dirofilariasis in dogs

A pet needs to regularly carry out antihelminthic preventive measures using drugs such as albendazole, ivermectin, levamisole, etc.

It is possible to suspect dirofilariasis in dogs by certain signs. Changes on the skin come to the fore: baldness, pigmentation, rashes, non-healing wounds, itching.

Gradually microfilariae affect the cardiovascular system of the dog. The pet becomes lethargic, passive, appetite disappears, the temperature rises, even with minimal physical exertion, a cough appears. Often the dog is lame, convulsions may appear.

First of all, it should be noted that in Russia this disease is rare. It is not surprising, therefore, that dirofilariasis in humans is difficult for most doctors to diagnose. What is it? The official name for dirofilariasis is "worm infestation caused by roundworms." As the main source of the disease, experts call street dogs and cats, as well as mosquitoes - insects are able to carry larvae and "implant" them under the skin. Of course, dirofilariasis, like other diseases of this kind, is most common in hot countries: in Africa, India, Vietnam. Recently, however, more and more cases of infection have been recorded in Russia.

Infection

As mentioned above, dirofilariasis in humans can develop dirofilaria larvae. It may take several months before they appear - this is how long the average incubation period lasts. Naturally, not all people will guess to connect the mysterious manifestations with a month ago.

Symptoms

Areas affected

Treatment

The only way to get rid of the larva is to remove it surgically. It must be emphasized that the use of antihelminthic drugs will not give any result.

Dirofilariasis: prevention

There is no specific prevention as such. It is impossible to be completely sure that the mosquito that has bitten you is not a carrier of larvae. All you can do is use insect repellant sprays and try to minimize skin exposure while in nature. In order to relieve itching, you can also use drugs that relieve allergic reactions. If they are not there, then an ordinary soda solution will do (they wipe the affected area). Don't want to let mosquitoes into indoor areas? Install and purchase several fumigators.

The relevance of the problem of dirofilariasis lies in the constant presence of obligate sources of the disease - animals - near a person and his dwellings, the wide distribution of dirofilaria both in animals and in general in natural conditions, low awareness of medical workers and the ingress of such patients not according to their profile, namely, to doctors of various specialties. For example, most patients with dirofilariasis go to doctors with diagnoses such as furuncle, phlegmon, atheroma, tumor, fibroma, cyst and others.

The first description of dirofilariasis dates back to 1855, when the removal of a worm from the eye of a sick girl by the Portuguese doctor Lusitano Amato was described. Then, with a certain frequency, similar cases are described in France, in Italy. In Russia, the first case of dirofilariasis of the eye was described in 1915 in Yekaterinodar by the doctor and scientist Vladychensky A.P. Since 1930, the founder of the helminthological school K.I. Scriabin and his students were closely involved in this problem.

Dirofilariasis, upper eyelid

Geographically, dirofilariasis occurs with a certain frequency in Central Asia, Georgia, Armenia, Kyrgyzstan, Kazakhstan, Azerbaijan, Ukraine, in the Russian Federation it is quite rare, mainly in its southern regions (Volgograd Region, Krasnodar Territory, Rostov Region, Astrakhan Region, and others). However, an analysis of the incidence of recent years has shown that a certain frequency of the disease is also present in areas with a temperate climate (Moscow region, Tula, Ryazan regions, Lipetsk region, the Urals, Siberia, Bashkortostan and others). On average, up to 35-40 cases of dirofilariasis are registered per year in Russia, and in some regions (for example, Rostov) - up to 12 cases per year.

Also, the disease is recorded with varying frequency in North America, Brazil, India, Australia, the African continent, Europe (Italy, Spain, France), Sri Lanka, as well as Canada, Japan. Iran and Greece are considered the most unfavorable for dirofilariasis.

Causes of dirofilariasis

The name of the disease comes from the Latin "diro, filium", which means "evil thread".
causative agent in humans- the larval stage (microfilaria) of a filamentous nematode (class Roundworms) of the genus Dirofilaria, which usually does not reach the sexually mature stage in the human body, with rare exceptions (more details in the development cycle).

The vast majority of cases are caused precisely by D. repens and D. Immitis, while the rest of the pathogens occur sporadically.

dirofilaria

A sexually mature individual up to 30 cm long and up to 1.5 mm wide, filiform with narrowed
ends. The female has a mouth, esophagus, intestines, nerve ring, vulva, oviducts, uterus and ovaries, while the male has papillae and spicules.

Larvae (or microfilariae) are microscopically small - up to 320 microns long and up to 7 microns wide, have a filiform appearance with a blunt anterior and pointed posterior end. However, due to their size, they can reach the blood and lymph with the current "the most remote corners of the human body."

Source of infection in dirofilariasis– an obligatory or obligatory source is domestic animals (dogs in the majority, less often cats - D.repens and D.immitis), isolated cases of the disease are also found among wild animals. The incidence of urban dogs varies from 3.5 to 30% depending on the region.

Dirofilariasis, source of infection - dogs

Intermediate hosts are mosquitoes of the genus Culex, Aedes, Anopheles - they carry invasive larvae (microfilariae) from animals to each other, as well as to humans. The infestation of mosquitoes by larvae varies from 2.5% (Anopheles) to 30% (Aedes). The role in the transmission of larvae and other blood-sucking insects - fleas, lice, horseflies, ticks - is not excluded. Man is an accidental and atypical host for dirofilaria larvae.

Dirofilariasis, vector of infection - mosquitoes

Mechanism of human infection- transmissible (through the bites of blood-sucking insects - mosquitoes and others), as a result of which the larvae from animals enter the human body.

Human susceptibility is universal. There is no dependence on age and gender, however, the majority of patients are in the age group from 30 to 40 years. There is a greater risk of infection in certain groups of people who have direct contact with heartworm vectors - mosquitoes. The risk group includes:
- fishermen, hunters, gardeners,
- pet owners (dogs and cats),
- living near rivers, lakes, swamps,
- lovers of tourism,
- workers of forestries, fish farms.

There is a seasonality of the greatest infection with dirofilaria larvae - the spring-summer period. The rise in the incidence is recorded in two waves: in April-May and October-November.

Development cycle of dirofilaria

A mature individual lives in the cavity of the right ventricle of the heart, as well as the right atrium, pulmonary artery, vena cava, and bronchi of animals. Dirofilaria release a large number of larvae (microfilaria-1) into the blood. Larvae are up to 320 microns long and up to 7 microns wide, that is, microscopically small. Larvae can penetrate into small vessels, various organs and tissues with the blood and lymph flow, and also be transmitted from mother to fetus. It is from the blood that blood-sucking carriers of mosquitoes and other insects swallow larvae during blood-sucking. During the day, microfilaria-1 are in the gut of the mosquito, and then penetrate into the cavities where they molt (microfilaria-2), then reach the lower lip of the mosquito and mature to the invasive stage (microfilaria-3). The duration of maturation in the body of a mosquito is on average 17 days. Then the mosquito sticks either to the skin of an animal or to a person and injects microfilariae-3. For 90 days, the larvae continue their development at the site of the bite (primary affect) - this is in the subcutaneous fat, where they molt twice more, which ultimately leads to the formation of microfilaria-5. In the future, it enters the bloodstream and spreads throughout the body, can settle in organs and tissues (more often this is the heart, pulmonary artery), where they mature to the sexually mature stage for another 3 months. Thus, the entire development cycle lasts up to 8 months. Microfilariae can circulate in the host's blood for up to 3 years.

Dirofilariasis, development cycle

The incubation period (from the moment of invasion to the appearance of the first symptoms) lasts from 30 days to several years and depends on the state of the human immune system.

Forms of dirofilariasis:

Dirofilariasis, ophthalmic form

With any of the forms of dirofilariasis, most patients also present general complaints - weakness, irritability, anxiety, sleep disturbances, headaches.

The literature describes rare cases of dirofilariasis - omentum, pleura, male genital organs (scrotum, testicles), fallopian tubes. Cases of dirofilaria lesions of the lungs, heart in humans are extremely rare.

Diagnosis of dirofilariasis

1) Primary diagnosis of dirofilariasis clinical and epidemiological. However, as a rule,
collection of an epidemiological history (presence of dogs near the dwelling, mosquito bites, visits to the forest, fishing, garden plots) is not very informative in terms of making a diagnosis. It is worth paying attention to the patient's stay in an endemic area during a period of high mosquito activity. Seasonality is also important information: with short incubation (up to 3 months from the moment of infection), the onset of the disease in June-July or October-November, and with long-term incubation (up to 8 months), the onset of the disease the next year after infection.
The main role is played by the complaints of patients: the appearance of subcutaneous nodes, which during the day can migrate at a distance of 10-30 cm, inside which there is a feeling of "crawling", as well as other characteristic complaints described above. Differential diagnosis is carried out with erythema nodosum, furuncle, carbuncle, abscess, allergic manifestations, conjunctivitis, choliasions (consequences of "barley" of the eye) and other diseases.

Dirofilariasis, microscopically

But doctors do not know everything about the life forms of dirofilaria in the human body, there are cases when all tests are within the normal range, and dirofilaria still lives under the skin - either crawls or lies in a capsule with microfilariae.

Dirofilaria after extraction from under the skin

Drug therapy is rare and ivermectin, diethylcarbamazine are used, but allergic reactions are possible during therapy.

Concomitant therapy: non-steroidal anti-inflammatory drugs, glucocorticosteroids, antihistamines, sedatives, and others.

With the ophthalmic form of dirofilariasis, the main method of therapy is the surgical removal of the helminth from under the skin of the eyelid, conjunctiva, followed by the appointment of disinfectants and anti-inflammatory drugs: drops of levomycetin, sulfacyl sodium, colbiocin, followed by the application of ointments (erythromycin, tetracycline). A number of patients require the appointment of a drop of dexamethasone in order to reduce inflammation. The entire period of therapy is supported by the appointment of antihistamines (Zyrtec, Claritin, Erius, Diazolin and others).

Most often, dirofilariasis in people affects the eyes, due to the fact that there is no official registration of helminthiasis, and medical workers are poorly informed, patients with signs of dirofilariasis in ophthalmologists are diagnosed with boils, cysts, phlegmon, and so on. In this regard, the treatment becomes more complicated and often the true diagnosis is dangerous for the patient.

Causes of the disease

The causative agent of dirofilariasis is a filamentous nematode, which is in the larval stage. Its size is 320 * 7 microns, the posterior end of the larva is slightly pointed, and the anterior end is blunt. When an individual reaches sexual maturity, it can be 30 cm long and 1.5 mm wide. Females have a mouth, esophagus, intestines, and reproductive organs. Males have spicules and papillae.

Cats are rarely carriers of dirofilariasis, mostly dogs are. If we talk about the intermediate host, then this is a mosquito, it is this insect that carries the larvae. Fleas, lice, ticks and horseflies and other insects that suck blood can also be carriers. A person for dirofilaria is not a typical host, not even an intermediate one, as a rule, this is an accidental host.

Description of the disease

Fishermen, summer residents, hunters, agricultural workers are people who are at risk. In addition, this group can include tourists, pet lovers and those who live near stagnant bodies of water.

Types of dirofilariasis

From where the pathogen is specifically localized in the human body, the types of dirofilariasis are determined.

Pulmonary. This view is also called the heart view. This name is given because this type of worm lives in the heart of dogs.
Extrapulmonary. It, in turn, is divided into subspecies: subcutaneous, ocular, cardiovascular, visceral - the worm lives in the liver, uterus or in the abdominal cavity.

To date, 4 cases of worm detection in human heart muscle have been recorded. 2 of them occurred in the USA, one in Brazil and one in Japan. There is a described case of detection of microfilariae in human blood, which means that the worm has reached puberty and began to multiply.

Many scientists believe that the statistics of people who suffer from pulmonary dirofilariasis are not accurate enough, the disease in most cases is asymptomatic, and besides, a mosquito that can feed on both dog and human blood can infect a large number of people with dirofilariasis.

Worm development cycle

Sexually mature individuals are most often localized in the heart or lung of their host, they lay larvae, which are carried throughout the body with blood flow and can enter any organ and vessel of the host. The mother can transfer the larvae to the fetus.

Mosquitoes, which are intermediate hosts, ingest the larvae when they suck blood from an animal. The first day the larva remains in the mosquito's stomach, and then molting occurs, and the larva gradually gets to the mosquito's lip, where the larva becomes a nematode.

After a bite, larvae are injected into the human blood and in the place where the bite was made, the larva remains for another 3 months. Thus, the larvae are already in the human subcutaneous fat. From there, the blood stream carries them throughout the body, and they can settle in organs and tissues. After 3 months, the larva can become a sexually mature individual, but this happens extremely rarely in the human body.

In addition, not a single case has been recorded when heterosexual individuals were found in the human body, so fertilization in the human body is very doubtful. The entire development cycle of dirofilaria takes 8 months.

Signs of disease in humans

Diagnosis and symptomatology of the disease is complicated by the fact that the incubation period of dirofilariasis can range from a month to several years. Therefore, the symptoms and treatment of the patient are delayed.

With skin dirofilariasis, the symptoms are characteristic of tissue helminthiasis. In the place where the worm is localized, a seal occurs, which, when palpated, responds with pain. In this place, suppuration may occur. Some say that they feel how the worm moves through the body.

In this case, there are no problems with visual acuity. Regardless of which organ the worm is located in, a person may experience anxiety and excessive irritability, chronic weakness and fatigue, sleep is disturbed, and signs of intoxication of the body appear.

If at least one of the symptoms listed above occurs, then a person is strongly recommended to consult a doctor and undergo an examination for dirofilariasis, treatment can be effective only if the diagnosis is correct.

Diagnosis of the disease

The main factor in the diagnosis are complaints and symptoms of the patient. For a more accurate diagnosis, the doctor must know if the patient has been in endemic areas, and whether he is at risk. Then the doctor examines the patient's eyes for the presence of nodes, and also examines the skin.

After all the studies, the doctor may prescribe treatment.

Treatment of dirofilariasis

When a doctor begins to treat dirofilariasis, he sets himself the following goals:

Subcutaneous dirofilariasis is treated in most cases on an outpatient basis, the patient undergoes all the necessary surgical procedures in a day. With pulmonary forms, treatment in a hospital is necessary.

The therapy is based on surgery, if the nodules are removed without problems, then no treatment is required after the operation. But before surgical manipulations, the doctor can prescribe drug therapy, if necessary. The most commonly prescribed are Diethylcarbamzine and Ivermectin.

Tetracycline antibiotics are a new approach for the treatment of dirofilariasis, they destroy the bacteria that secrete filariae, at the same time the worms themselves die, because the bacteria are their symbionts.

If the diagnosis is wrong, then the treatment will be irrational. In medical practice, there was a case when a patient's breast was removed, suspecting she had oncology, after the operation it turned out that it was a helminth lesion. Therefore, it is very important to conduct a correct and thorough diagnosis in order to avoid such errors.

How is the operation performed

When the helminth is localized in the eye, the doctor removes the worm with special tools, after which the patient takes anti-inflammatory and disinfectants. Treatment of the eye is shown, for example, with drops of Dexamethasone. A course of antihistamines is required.

The prognosis in the vast majority of cases is favorable. Any complications are extremely rare. This may be a pulmonary infarction or non-specific respiratory symptoms, there are also reports of intraocular infections.

What is dangerous

No lethal outcomes have been described, the worst that pulmonary dirofilariasis can lead to is a wedge-shaped resection of the area affected by the worm in order to prevent more serious pathology. Internal hemorrhages can be caused by the visceral form.

Animal diagnostics

To reduce the risk of infection with dirofilariasis, you need to carefully examine your pet, in an animal with signs of the disease, skin rashes, seals, wounds and small tumor formations can be observed. If helminths live in the heart muscle of an animal, then the animal becomes passive, it loses its appetite, coughs, and the temperature may rise. In severe cases, the dog may experience seizures and lameness.

For the prevention of helminthiasis in dogs and cats, it is necessary to give the animal anthelminthic drugs in a timely and regular manner. How often to give the drug, and in what dosage, is determined by the veterinarian. It is also important to take measures against fleas and ticks. Treat the coat with special products, comb it out or put on an anti-flea collar.

Video

It is noteworthy that the probability of infection with larvae is much higher in the spring-autumn period of the year. With proper diagnosis and timely operation, you can completely recover from this disease, which will not leave consequences in the form of complications or any restrictions in a person's life.

Etiology

The cause of the development of dirofilariasis is the bite of an insect that had previously had contact with infected dog feces, less often cats.

Middle-aged people, from thirty to forty years old, are susceptible to the appearance of such a disease. But there are some groups of people who are most likely to come into contact with a carrier. These groups include:

people with whom cats or dogs live in a house or apartment;
fishermen and hunters;
those who live in close proximity to water bodies of any size;
lovers of this type of recreation, such as tourism;
workers of agricultural lands and fish farms, as well as gardeners.

In the human body, the disease can progress in two forms - ophthalmic and subcutaneous. Less commonly, there is damage to the mammary glands and scrotum. In a few days, the worm can travel a distance of up to thirty centimeters.

Symptoms

But in almost all known clinical cases, the manifestation of dirofilariasis entails the appearance of such symptoms:

general weakness of the body;
Strong headache;
nausea and vomiting;
a slight increase in body temperature;
pain in the place where the worm is located;
pain and swelling of the eyes;
split vision;
sleep disturbance;
irritability;
sensation of stirring under the skin or in the eyes.

Diagnostics

Diagnosis of dirofilariasis can be carried out in several ways:

The main way to confirm the diagnosis is a complete examination of the worm that was withdrawn. Therefore, only after the operation, the patient is diagnosed with dirofilariasis.

Treatment

It is impossible to get rid of the worm except by surgery. The exception is those cases when a purulent bulge forms from being under the skin of a worm, which may burst on its own. Then the worm can start crawling out on its own. In the event that the purulent formation burst and the contents leaked out, but the worm was not there, you need to urgently go to the hospital for medical help.

Since it is possible to diagnose dirofilariasis only after surgery, doctors can treat the patient completely for other diseases. Very often it turns out to detect a large worm during the passage of a planned x-ray. But in medical practice, more than half of the cases of determining dirofilariasis occur during other operations.

Only after an ophthalmological examination is it possible to determine exactly where the worm is in the eyeball - near the pupil or under the upper eyelid. After removing the worm from the eye, the patient, as a treatment, is prescribed special eye drops, ointments, which will need to be laid behind the eyelid.

Prevention

Basically, the prevention of dirofilariasis is aimed at:

limiting contact with pets;
timely treatment of this disease in dogs and cats;
personal protection against mosquito bites, in the form of aerosols, ointments and protective clothing.