Dirofilariasis
The content of the article:
- Causes and risk factors
- Forms of the disease
- Symptoms
- Diagnostics
- Treatment
- Possible complications and consequences
- Forecast
- Prevention
Dirofilariasis is a transmissible zoonotic helminthiasis provoked by the roundworms (nematodes) Dirofilaria (dirofilariae), which are characterized by parasitism in the subcutaneous fat, less often in the internal organs of a person.
Cutaneous form of dirofilariasis
The term "vector-borne infections" refers to infectious diseases, the causative agents of which persist in the body of blood-sucking insects and ticks; human infection in this case, respectively, occurs with a bite. The carrier (intermediate host) of dirofilaria larvae (their other name is microfilariae) are some species of mosquitoes (Aedes, Anopheles, Culex), fleas, ticks and other arthropods.
Zoonotic diseases are characterized by the presence of any animals as a natural reservoir (long-term host of the pathogen in which it can carry out continuous existence). The main owners of dirofilaria are dogs and other canids, less often cats become owners.
Dirofilariasis is recorded in more than 20 regions of Russia, the average detection rate of the disease per year is 40-50 cases, and helminthiasis is observed much more often in the southern regions.
When an infected insect bites, in 100% of cases, a person is infected, there is no immunity to this disease.
Causes and risk factors
The cause of the disease is the ingestion of a roundworm larva (dirofilaria) into the human body. Sexually mature dirofilaria is a long filamentous worm (from 14–17 to 30 cm), extremely thin (the size of an individual does not exceed 0.5 mm in diameter). The size of the larvae usually does not exceed 350 microns, which allows them to circulate freely in the systemic circulation.
There are 6 types of pathogens parasitizing in the body of one or another (species-specific for helminth) animal (Dirofilaria ursi - in the body of a brown bear, Dirofilaria tenuis - raccoon, Dirofilaria subdermata - porcupines, etc.).
The cause of dirofilariasis is the ingestion of a round worm (dirofilaria) into the human body
Despite the wide species diversity of helminths, the main provocateurs of the disease are Dirofilaria repens and Dirofilaria immitis, parasitizing in the organisms of cats and dogs.
In the body of the main host (cats, dogs), sexually mature individuals of dirofilaria colonize large blood vessels, chambers of the heart, and organs of the respiratory system. After fertilization, the female worm is released into the bloodstream up to 30,000 microfilariae per day, where the larvae continue to circulate for an average of 2-2.5 years unchanged or until the transition into the body of a blood-sucking insect. When an infected animal is bitten, the larvae with infected blood migrate into the insect's body.
In the intestines of arthropod insects, the transformation of microfilariae begins, from where, within a few days, they move to the lower lip of the insect, evolving into an invasive (capable of causing disease) stage. The maturation of the helminth larva in the blood-sucking body lasts a little more than 2-2.5 weeks, after which, at the time of the bite of a person or animal, it passes into the bloodstream of the bitten individual.
At the site of the bite (in the subcutaneous fat), the parasite matures and sheds for 3 months, after which the dirofilariae spreads through the organs and tissues with the blood flow. Having settled at the final point of localization, the helminth matures into a sexually mature individual capable of reproduction over the next 90 days, after which its life cycle repeats.
In most cases, a person is a dead-end branch for microfilariae, since the reproduction of new larvae in this case is extremely difficult: at the time of penetration, most microfilariae die, which leads to a low probability of the possibility of fertilization in the future. The symptomatology of the disease is due to the presence in the body of one or more sexually mature individuals, although cases of microfilaremia (circulation of larvae in the human systemic circulation) have been extremely rare.
Forms of the disease
There are 2 main forms of the disease:
- cutaneous, when the helminth parasitizes the skin and subcutaneous fat;
- ophthalmic, in which case the dirofilarium is introduced into the eyeball or under the conjunctiva.
Ophthalmic form of dirofilariasis
Symptoms
Symptoms vary depending on the form of the disease.
Manifestations of cutaneous dirofilariasis:
- a small painful lump under the skin (from a few mm to 1-1.5 cm), as a rule, coinciding with the site of the insect bite;
- a feeling of movement inside the skin nodule;
- paresthesia (a feeling of "creeping");
- the ability of the seal to migrate under the skin (up to several tens of cm per day).
Cutaneous dirofilariasis is manifested by paresthesias and painful lumps under the skin
Symptoms of ocular dirofilariasis (on the side where the parasite was introduced):
- pain in the eyes;
- feeling of sand or foreign body;
- injection of the conjunctiva (redness of the whites of the eyes due to the expansion and increased blood filling of local vessels);
- swelling of the eyelid;
- lacrimation;
- inability to fully open the affected eye;
- soreness when moving the eyeball;
- feeling of movement, stirring in the place of defeat.
Sometimes, with this form, upon visual inspection, you can see a thin coagulated worm under the conjunctival membrane or thin skin of the eyelid.
In addition to specific local manifestations, patients may have general intoxication symptoms of mild severity: a slight increase in body temperature, fatigue, headache, drowsiness, loss of appetite.
It is extremely rare that dirofilariae are found not only in the organs of vision and skin, but also in the internal organs.
Diagnostics
Diagnosis of the disease is based on a thorough collection of an epidemiological history (information about previous insect bites), laboratory and instrumental research methods:
- general blood test [for nonspecific signs of the inflammatory process (leukocytosis, accelerated ESR), an increase in the number of eosinophils];
- enzyme-linked immunosorbent assay (ELISA) for the detection of dirofilarial antigen;
- polymerase chain reaction (PCR), which allows the detection of parasite DNA;
- immunoblotting (diagnostics of specific antigens);
- microscopic examination of the parasite extracted from the seal;
- Ultrasound examination;
- if necessary, magnetic resonance imaging or computed tomography.
ELISA analysis allows you to identify a dirofilarial agent in the blood
Treatment
The main method of treatment is the surgical removal of the helminth from the soft tissues or the patient's eyeball.
As a conservative therapy, it is possible to use antiparasitic anthelmintic drugs.
Concomitant therapy is represented by the following groups of drugs:
- antihistamines;
- sedatives;
- analgesics;
- anti-inflammatory drugs;
- local glucocorticosteroids (if necessary).
Possible complications and consequences
Complications of dirofilariasis can be:
- suppuration of the subcutaneous formation;
- allergic reactions.
Forecast
The forecast is favorable. Even in the case of untimely detection and extraction of the helminth, with its long persistence in the human body, no significant painful manifestations were noted.
Prevention
Preventive measures are as follows:
- Restriction of the population of stray animals (according to studies, the infection rate of stray animals exceeds 30%).
- Extermination of mosquitoes, ticks.
- The use of personal protective equipment during prolonged exposure to the open air (repellents - creams, sprays, aerosols).
- Protecting pets from insect bites.
- Annual deworming of pets.
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Olesya Smolnyakova Therapy, clinical pharmacology and pharmacotherapy About the author
Education: higher, 2004 (GOU VPO "Kursk State Medical University"), specialty "General Medicine", qualification "Doctor". 2008-2012 - Postgraduate student of the Department of Clinical Pharmacology, KSMU, Candidate of Medical Sciences (2013, specialty "Pharmacology, Clinical Pharmacology"). 2014-2015 - professional retraining, specialty "Management in education", FSBEI HPE "KSU".
The information is generalized and provided for informational purposes only. At the first sign of illness, see your doctor. Self-medication is hazardous to health!
