Vuhereriosis is an anthroponotic natural focal biohelminthiasis with a transmissive transmission mechanism. Characteristic symptoms of the disease are allergic reactions, the presence of lymphangitis, lymphadenitis with the gradual formation of elephantiasis mainly of the lower extremities and scrotum. Diagnosis is based on the detection of the parasite itself, as well as its antigens and antibodies in the patient’s blood. Treatment is carried out with diethylcarbamazine, albendazole and ivermectin. According to the indications, symptomatic therapy is prescribed (taking antihistamines, antipyretics, corticosteroids). With the formation of ulcers, severe forms of lymphedema, surgical treatment may be required.
B74.0 Filariasis caused by Wuchereria bancrofti
The focus of vuhereriosis is the territories of tropical and subtropical climate (Africa, South America, India, South and East Asia, islands of the Pacific and Indian Oceans). Susceptibility is universal, men are more often ill. Seasonality is not pronounced, the incidence is associated with the activity of mosquitoes. The local population mainly suffers from erased forms due to repeated infections and circulation of specific antibodies in the blood. In the acute form, the disease is more often carried by immigrants. According to the latest data, about 80 million people are infected with lymphatic filariasis. a person of endemic areas, clinical manifestations are observed in 15% of them. Since 2000 WHO is actively developing a program to eliminate the disease with mass coverage of the local population with chemoprophylaxis.
Causes of vuhereriosis
The causative agent of helminthiasis is the nematode Wuchereria bancrofti (Bancroft’s filamentum) from the Filarudae Cobbold family. The length of the female can reach 10 cm, the male – 3-4 cm. Females give birth to microfilariae larvae. Sexually mature parasites live in lymph nodes and vessels, and larvae live in the host’s blood. The development of nematodes occurs with the change of hosts. The reservoir and source of vuhereriosis is an infected person and some species of monkeys. The disease is transmitted with a mosquito bite.
When an infected person is bitten, microfilariae enter the mosquito’s body. After passing the development cycle to the invasive stage (about 40 days), the larvae enter the proboscis of the insect. Thus, a healthy person becomes infected with a new bite. Localization of microfilariae in the human body depends on the activity of mosquito vectors. During the day, the larvae are in the vessels of internal organs, and at night they migrate to the subcutaneous ones in order to get into the insect’s body during the greatest activity with a bite. In the body of the host, adults can live up to 7-8 years, in some people they parasitize up to 20 years; the life span of the larva is up to 6 months.
During a mosquito bite, microfilariae enter the human bloodstream. In his body, during the stages of development to mature individuals, larvae secrete metabolic products. This is associated with the first clinical symptoms in the form of toxic-allergic reactions due to sensitization by foreign substances. Adult nematodes live in lymphatic vessels. Forming tangles, they block their lumen. The vessels dilate, often burst, their wall becomes inflamed. Relapses of infection contribute to thrombosis and sclerosis of lymphatic vessels, which ultimately leads to lymphostasis. The phenomena of fibrosis and necrosis are also noted in the lymph nodes. Altered vascular walls, as well as open wounds, serve as a place of attachment of secondary infection.
Symptoms of vuhereriosis
The incubation period is 5-6 months, for indigenous people it can be delayed for decades. There are periods of acute and chronic manifestations. The acute period lasts from several weeks to several years. Symptoms of an allergic reaction are characteristic: fever, myalgia, headache, skin rashes such as exudative erythema. Many patients have so-called tropical pulmonary eosinophilia. This symptom complex includes nocturnal coughing attacks, subfebrile body temperature, weakness, signs of miliary lung damage on an X-ray.
There is a local reaction from the tissues in which the pathogen is located. Lymphangitis and lymphadenitis develop. Lymph nodes are painful, the skin over inflamed structures is hyperemic, edematous. The inguinal nodes are most often affected. Funiculitis, orchiepididymitis, synovitis occur, a hydrocele is formed, the labia can swell in women, as well as mammary glands with the formation of mastitis. Such acute phenomena last from several hours to several days. Then the process regresses. The frequency of relapses ranges from single attacks per year to monthly exacerbations.
Against the background of constant activation of the inflammatory process, varicose lymphatic vessels develop. Often the vessels burst, ulcers appear on the skin with the expiration of lymph. When the deep lymph nodes are affected, the attacks may resemble malaria (pronounced intoxication on the background of fever, followed by sweating), and when the lymphatic structures of the abdominal cavity are involved, an acute abdomen. In the acute period of vuchereriosis, the phenomena of obstruction of the lymph flow are reversible, however, with repeated inflammations, fibrosis of blood vessels and lymph nodes is formed, they are replaced by connective tissue strands, lymphostasis occurs, lymphedema (elephantiasis) develops, a chronic form occurs.
Elephantiasis (elephantiasis) is more characteristic of the lower extremities, genitals, the upper eyelid is most often affected on the face. Objectively, the limbs become enormous, the skin becomes covered with warty growths, many non-healing ulcers are formed. Due to the rupture of the lymphatic vessels of the internal organs, chyluria is formed (lymph excretion with urine when the vessels of the kidneys and bladder are ruptured), chyletic diarrhea, ascites, peritonitis. Chyletic impregnation of the scrotum – lymphoscrotum – is also characteristic of the chronic stage. In the case of the development of such pathology, the weight of the scrotum can reach 15-20 kg.
The most common complication is the attachment of infection at the site of rupture of the lymphatic vessel with the formation of lymphangitis, thrombophlebitis, gangrene, sepsis. In addition, lymph is a protein-rich fluid. With constant loss due to vascular damage, progressive protein deficiency develops, patients lose weight, and cachexia occurs.
Due to the obstruction of the urinary tract by blood clots and lymph, acute urinary retention is often noted. Zones of aseptic inflammation appear around the bodies of dead nematodes in the internal organs of a person. Infection of such structures leads to the development of abscesses. Upon self-opening of the formed ulcers, pleural empyema, peritonitis, purulent arthritis are formed in the serous cavities. The breakthrough of lymph into the lumen of internal organs leads to chyluria, chyletic ascites, diarrhea.
If there is a suspicion of vuchereriosis, it is mandatory to consult an infectious disease specialist, a parasitologist, followed by hospitalization of the patient in an infectious hospital. In the case of the formation of elephantiasis, a surgeon’s examination is necessary. The physical examination data depends on the stage of the disease. In the acute phase, the symptoms of a toxic-allergic reaction come first, and in the chronic phase – the consequences of lymphostasis.
Objectively, palpation usually determines a unilateral enlargement of the inguinal lymph nodes. Knots are painful. The presence of varicose dilated lymphatic vessels is noted on the lower extremities. There are wounds with lymph leakage at the site of their rupture. At the stage of the formation of elephantiasis, the lower extremities, mainly the lower legs and feet, are of enormous size, there are many warts, trophic ulcers on the skin. The scrotum, penis, labia majora are significantly enlarged, swollen. The mammary glands may fall below the waist. The following clinical and laboratory methods are used in diagnostics:
- Clinical and biochemical studies. In a general blood test with exacerbation, the presence of eosinophilia is characteristic, signs of inflammation are possible; with the progression of protein deficiency, a decrease in the level of total protein and fractions is noted. In the analysis of urine, hiluria is determined.
- Detection of the pathogen. For the direct detection of the parasite, smears or preparations of a thick drop of blood are examined. Microfilariae are determined by microscopy. Blood for such studies should be taken at night or during the day when conducting a provocative test with diethyl carbamazine.
- Identification of infectious markers. Rapid ELISA tests, a method of rapid immunochromatography, are used to detect specific antigens. The antibody titer is determined using ELISA, NRIF. Identification of nematode DNA is performed by PCR.
- Ultrasound examination. Ultrasound of lymph nodes, organs of the scrotum, lymph vessels of the extremities is performed. An important sonographic sign of vuhereriosis is the detection of moving microfilariae and adult parasites in lymphatic structures.
Differential diagnosis of vuhereriosis should be carried out with bacterial lymphangitis, as well as with the causes of nodular lymphangitis, such as sporotrichosis and leishmaniasis. It should be borne in mind that serological diagnostic methods can give cross-reactions with Strongyloides stercoralis antigens. Pulmonary eosinophilia must be distinguished from tuberculosis. It is important to distinguish chronic forms of vuchereriosis from diseases that can cause lymphostasis (hereditary pathologies of lymphatic vessels, chronic heart failure, varicose veins of the lower extremities).
Treatment of vuhereriosis
All infected people must be hospitalized and isolated. Treatment is aimed at the destruction of both larvae and adults. The main drug is diethylcarbamazine. It is taken orally at 6-7 mg / kg / day for 14 days or according to a scheme with a gradual increase in the dose. The decay products of nematodes can cause allergic reactions, so the drug is prescribed together with antihistamines and glucocorticosteroids. According to the indications, symptomatic treatment is carried out (taking antipyretic drugs, opening and drainage of abscesses).
When using diethylcarbamazine, adverse reactions in the form of itching, lymphadenopathy, hepatomegaly and splenomegaly are often observed. In addition, with concomitant onchocerciasis, irreversible eye damage may develop. In order to reduce undesirable effects, alternative schemes have been developed with the addition or isolated use of albendazole and ivermectin. Manifestations of the chronic stage of vuhereriosis are not cured by these medications. Drugs are prescribed in order to prevent further progression of the process. Surgical correction of lymphostasis, as well as wearing bandages, contributes to improving the quality of life.
Prognosis and prevention
If the disease is recognized in time and therapy is started in a timely manner, the prognosis is favorable. Fatal cases are most often associated with the development of infectious complications. Measures of non-specific protection are aimed at the destruction of mosquito breeding sites, isolation and treatment of patients. In countries endemic to vuchereriosis, it is necessary to use mosquito nets, repellents. Chemoprophylaxis with diethyl carbamazine or albendazole with ivermectin is widespread among the local population. As part of the WHO program for mass coverage of the population in order to prevent the development of the disease, diethyl carbamazine is used as an additive to salt throughout the year. Biological preparations for specific prevention have not been developed.