Vukhereriosis (filariasiasis): causes, symptoms, diagnosis, treatment

Filariasi - a group of transmissible helminthiases, prevalent mainly in countries with a tropical and subtropical climate. Endemic foci of filarias of the lymphatic system are found in 73 countries. According to the WHO, 120 million people are infected with these helminthoses, and 1100 million live in the risk zone.

Vukhereriosis - transmissible filariasis, biogelmintosis, anthroponosis. Adult individuals live in lymphatic vessels, and larvae (microfilariae) in the blood.

The cycle of development of VUCERIERIOSIS

Infection with vecherryosis occurs when a person bites mosquitoes of genera Culex, Anopheles, Aedes or Mansonia. Vucereria is a biogelmint, in the cycle of its development there is a final and intermediate host. The final (definitive) host is a person, intermediate - the mosquito of the genera Culex, Anopheles, Aedes or Mansonia.

At the time of human bite, invasive larvae (microfilariae), located in its mouth organs, tear the skin of the proboscis, get on the skin and actively penetrate into it. With the blood flow, they migrate to the lymphatic system, where they grow, molt, and after 3-18 months they become sexually mature males and females. Male and female are located together, forming a common tangle.

Vuchereries are viviparous. Sexually mature helminths are localized in peripheral lymphatic vessels and nodes, where females give birth to live larvae of the second stage (microfilariae), covered with a sheath. Larvae migrate from the lymphatic system to the blood vessels. During the day they are in large blood vessels (carotid artery, aorta) and vessels of internal organs. At night, the larvae migrate to the peripheral blood vessels, and therefore they are called Microfilaria nocturna (night microfilariae). The daily migration of larvae is associated with night activity of mosquitoes (carriers of the causative agent of vucereriosis).

When a sick person bites a female mosquito, microfilariae enter the digestive tract of an insect, discard the cover, penetrate through the wall of the stomach into the body cavity and pectoral muscles. In the muscles, the larvae moult twice, become invasive larvae of the fourth stage, and penetrate the mosquito's oral apparatus. The duration of the development cycle of larvae in mosquitoes depends on the temperature and humidity of the environment and varies from 8 to 35 days. Optimal conditions for the development of invasive larvae are temperature 29-30 ° C and humidity 70-100%. In the body of a mosquito, the larvae remain viable throughout life.

The life expectancy of adult helminths in the human body is about 17 years. Microfilariae retain viability in the bloodstream for about 70 days.

Epidemiology of vukhereriosis

Endemic foci of wuchereriasis occur in countries with a tropical and subtropical climate. Vuchereriasis is common in Western and Central Africa, Southeast Asia (India, Malaysia, China, Japan, etc.), South and Central America (Guatemala, Panama, Venezuela, Brazil, etc.), on the islands of the Pacific and Indian Oceans. In the Western Hemisphere, the area of Vucererioz is limited to 30 ° N. W. And 30 ° S. And in the Eastern hemisphere it is 41 ° N. W. And 28 ° S. W.

Vucererioz is mainly a disease of the urban population. The growth of large cities, population crowding, lack of sanitary control, contaminated water reservoirs, abandoned water supply and sanitation systems favor the reproduction of mosquitoes.

In the developing countries of Asia and Africa, where cities and towns are being built, infection with wuchereriasis is increasing.

The source of the disease is infected people. The carrier of the pathogen in urban conditions is most often mosquitoes of the genus Culex. In rural areas in Africa, South America and some Asian countries, vetcheriosis is mainly carried by mosquitoes of the genus Anopheles, and in the Pacific islands - the genus Aedes. Infection of a person occurs due to penetration of invasive larvae with a mosquito bite.

What causes vukhereriosis (filariadosis)?

Vuchereriasis is caused by Wuchereria bancrofti, has a threadlike body of white color, covered with a smooth cuticle, thinner at the cephalic and caudal ends. The length of the female is 80-100 mm, width - 0.2-0.3 mm, and the males - 40 mm and 0.1 mm, respectively. Usually males and females intertwine, forming tangles. Larvae (microfilariae) are covered with a transparent sheath and have a length of 0.13-0.32 mm and a width of 0.01 mm.

Pathogenesis of vucereriosis

In the early stage of the disease, there are symptoms of vukherriosis in toxic-allergic reactions: fever, swelling, rashes on the skin, eosinophilia of the blood, etc. Later (2-7 years), inflammation of the skin and deep lymph vessels develops. Lymphatic vessels, in which adult parasites are located, expand, thicken, walls are infiltrated by lymphocytes, eosinophils. Around the helminths, granulomas form. The dead helminths are lysed or calcified and are surrounded by a fibrous tissue. Necrosis with edema and pus may develop on the site of death. Granulomatous lymphangitis and lymphadenitis develop. Lymph nodes increase, become painful, edema of surrounding tissues develops. Lymph nodes and lymphatic vessels of the lower extremities and urogenital organs are more often affected. With intensive invasion, lymphatic vessels clog, leading to a violation of lymph drainage, resulting in swelling of the body (elephantiasis). Sometimes vukererioz is complicated by the attachment of a secondary infection.

Symptoms of VUCERIERIOSIS

Symptoms of vucereriasis depend on the individual immune response caused by various factors - age, degree of infection, etc. The course of this disease is polymorphic. The incubation period of vukhereriosis, lasting from 3 to 18 months, is asymptomatic. In people living in endemic areas and infected with microfilariae, the symptoms of the disease may be absent. This is due to the fact that the indigenous inhabitants of these areas due to re-invasion developed partial immunity. The incubation period for local residents lasts 12-18 months. Visitors of nonimmune citizens with a mild invasion of a disease may have a skin itch; their incubation period is shorter and lasts 3-4 months, which corresponds to the time from penetration of invasive larvae into the human body before the birth of microfilaria by sexually mature females.

In the clinical course of vukhereriosis, acute and chronic forms are isolated.

The acute form of the disease is characterized by the symptoms of vukhereriosis in the form of allergic manifestations, which are caused by an increased sensitivity of the organism to the helminth. At this stage, lymphadenitis, lymphangitis in combination with fever and malaise develop. The lymphatic system is more often affected in men and manifested by furunculitis, epididymitis, orchitis. The frequency of exacerbations of adenolymphangitis varies from 1-2 per year to several per month. During exacerbations there is lymphatic edema, which gradually disappears. With the passage of time, the disappearance of the edema is incomplete and the disease becomes chronic.

The chronic form of vukererioz develops in 10-15 years from the moment of infection. It is accompanied by the development of persistent edema and elephantiasis (elephantiasis) arising from the progression of lymphostasis, proliferative processes and fibrosis in the skin and subcutaneous tissue. The size of the affected organs (scrotum, lower extremities, mammary glands) is greatly increased. With elephantiasis of the scrotum, its mass can reach 3-4 kg, sometimes 20 kg or more. At local residents elefantiaz it develops less often and more slowly, than at visitors.

With chronic vukhererioz often develops edema of the testicles (hydrocele). In a punctate liquid, microfilariae can be detected.

Sometimes there is hiluria (the presence of lymph in the urine), manifested in milky white color of urine, chile diarrhea (diarrhea with an admixture of lymph). This leads to hypoproteinemia due to protein loss and weight loss in patients.

Among the residents of endemic foci of vukhereriosis in South and South-East Asia, the syndrome of "tropical pulmonary eosinophilia" is characterized by the presence of poly-lymphadenitis, hepatosplenomegaly, subfebrile fever, night attacks of coughing, difficulty breathing due to bronchospasm, dry wheezing. There is also an increase in ESR and pronounced eosinophilia (up to 20-50%). In the absence of treatment and progression of the disease, pulmonary fibrosis develops.

With prolonged course of the disease, patients may develop symptoms of vecherryosis, which are a consequence of glomerulonephritis, endomyocardial fibrosis, eye damage (conjunctivitis, iridocyclitis), and secondary infection (abscesses of internal organs, peritonitis).

Complications of VUCERIERIOSIS

The complications of vukhereriosis are associated with the lesion of the lymphatic system (elephantiasis). Sometimes there is a blockage of the ureters by coagulants, limb function disorders in the formation of scars in the joint area, attachment of a secondary infection with the development of acute bacterial lymphangitis and thrombophlebitis.

Vucerioriosis is characterized by a prolonged course. Elephantiasis leads to loss of ability to work. Lethal outcomes occur as a result of secondary infection.

Diagnosis of wuchereriosis

Vuchereriasis is differentiated with tuberculosis of lymph nodes, lymphocytic leukemia, infectious mononucleosis, bubonic plague form and other filariasis.

The diagnosis is based on an epidemiological history, clinical data, the results of instrumental and laboratory research methods.

Laboratory diagnostics of vukhereriosis 

Confirmation of the diagnosis is the finding of microfilariae in the blood. The blood test is carried out in a fresh drop deposited on a slide, under a small increase in the microscope (blood sampling is carried out in the evening or at night). Diagnosis of Vuchereriasis consists in using the method of enrichment. Sometimes immunological methods are used, however they are not strictly specific.

Treatment of VUCERIERIOSIS

Treatment of vukhereriosis is complex. It is spent in a hospital. Treatment of vecherryosis includes de-worming, suppression of bacterial infections, easing of allergic reaction. Often you have to resort to surgery. Lymphadenitis is treated with antihistamines and analgesics. Diethylcarbamazine (DEK, ditrazine) is effective against microfilariae and sexually mature individuals (microfilaria die quickly, and mature individuals within 2-3 weeks). On the first day, 50 mg of the drug is administered orally once after meals, 2 times at 50 mg 3 times, and from 4 to 21 days of treatment, 2 mg / kg 3 times per day. The maximum daily dose is 400 mg. The duration of treatment of vukhereriosis is 21 days. Children prescribe the drug at 2 mg / kg 3 times a day for 10-14 days. According to clinical indications, repeated courses of treatment are prescribed. Depending on the effectiveness of 3 to 5 courses of treatment with intervals of 10-12 days. Mass death of microfilariae at the beginning of treatment can be accompanied by an allergic reaction (fever, urticaria, lymphangitis). For effective treatment, corticosteroids are used. The hydrocele is effectively treated by surgical methods.

How to prevent vukhereriosis?

Early diagnosis and treatment of vecherryosis prevents the development of elephantiasis. Vuhereriosis can be prevented if individual protection against mosquito bites is observed. To do this, apply repellents, special types of clothing, bed-curtains. To combat mosquitoes, landscaping of sewerage and water supply systems in cities and towns is carried out. Destroy the site of the breeding of mosquitoes with the help of insecticides.

A set of measures for the prevention of vukererioz includes the identification and treatment of patients, as well as measures for the destruction of mosquitoes. Conduct mass surveys of the population to identify individuals with microfilaria in the blood and their subsequent treatment. For mass chemoprophylaxis of lymphatic filariasis in endemic areas, diethylcarbamazine (DEC) is used. All residents once a year appointed in a dose of 2 mg / kg orally in three divided doses for one day.