What is Wuchereriasis (Elephant Disease)?
Wucareriasis (elephantiasis, elephant disease) – helminthiasis, is caused by filamentous helminths – filarias that circulate in the blood.
It is estimated that about 80 million people worldwide are infected with wusheriasis.
Causes of Wuchereriasis (Elephant Disease)
The causative agent of wuchereriasis is the Bancroft filament (Wuchereria bancrofti), common in the tropics and subtropics. In the former USSR, elephant disease was found in isolated cases in Central Asia. Adults are most commonly found in the lymphatic glands and vessels. As a result of blockage of the lymphatic vessels, inflammatory thickening of their walls occurs, as well as stagnation of the lymph. The affected areas greatly increase in size.
Females produce a huge number of larvae, each about 0.3 mm long. They are called “night microfilariae”, as they appear at night in peripheral blood, on the day they go deep into the body and are held in the pulmonary vessels, heart and kidneys. This periodicity is associated with the peculiarities of the transmission of parasites, which occurs through intermediate hosts, namely, various blood-sucking mosquitoes. When mosquitoes suck in the evening or at night the blood of carriers of filarias, the larvae enter the mosquito’s stomach and then penetrate into the cavity of its body. There they grow somewhat and eventually accumulate at the base of the piercing insect’s proboscis. When sucking the blood of a healthy person, such a mosquito pierces into the skin the piercing bristles of its proboscis; at this time, the larvae of the filariala come out of the trunk and actively penetrate the skin, then getting into the blood.
Wuchereria bancrofti is most common among filarial parasites in humans. The parasite is found in the tropics and subtropics – Asia, Oceania, Africa, places in South America and in the Caribbean.
The man is the only final owner of the Wuchereria bancrofti. Adult worms live in humans up to 17 years old, the larvae in the bloodstream – up to 70 days. It is estimated that 120 million people are infected with wucarariosis.
According to the terminology adopted by the WHO Expert Committee on Filariasis, periodic and sub-periodic microfilaria strains are distinguished. Microfilariae Wuchereria bancrofti of the periodic strain (Microfilaria nocturna) are found in the vessels of the lungs during the day, and at night they move to the peripheral vessels. The microfilariae of the Wuchereria bancrofti subperiodic strain, identified in the Pacific Ocean zone and therefore called W. pacifica, are in peripheral blood around the clock, but during the day their number increases markedly.
Pathogenesis During Wuchereriasis (Elephant Disease)
The source of wuchereriasis is a sick person or a parasitic carrier, the source of brughosis is a person and some monkeys. The direct carriers of infection are mosquitoes.
The causative agent of wuchereriosis, Wuchereria bancrofti, is transmitted by many species of mosquitoes, most often Culex fatigans, S. pipiens, Aedes polynesiensis. The development of microfilariae in mosquitoes lasts 8-35 days, depending on the ambient temperature. When a mosquito bites, invasive forms of microfilariae enter the skin, are actively implanted in the bloodstream and are brought into the tissues by blood flow. The transformation of microfilariae into mature forms occurs 3-18 months after they enter the human body.
The basis of the pathogenesis of wuchereriasis are toxic-allergic reactions, the mechanical effect of helminths on the lymphatic system and secondary bacterial infection. Like many other helminthiasis, wuchereriasis in some cases may not give a pronounced clinical picture. Sometimes there are no clinical manifestations of invasion at all. Asymptomatic vukheririoz occur in cases where the parasites do not clog the lymphatic vessels and do not cause inflammatory changes in the surrounding tissues. Patients with such forms of infection are detected by chance when they detect microfilariae in peripheral blood.
Vukherii in lymphatic vessels, including in the thoracic duct, intertwine into balls, which cause a slowing of the lymph flow and lymphostasis. Parasites cause inflammatory sealing of the walls of the lymphatic vessels, which ultimately leads to blockage of blood vessels as a result of stenosis or thrombosis. Thrombosed lymphatic vessels often rupture. Due to prolonged lymphangitis and lymphadenitis, elephantiasis (elephantiasis) can develop in various parts of the body. Modified endothelium of lymphatic vessels, foci of necrosis in lymph nodes and surrounding tissues are favorable places for the development of coccal infection with the formation of abscesses. As a result of the vital activity of parasites and, especially, when they decay, substances are formed that lead to the sensitization of the body with local and general allergic reactions – eosinophilia, skin rashes, etc.
Symptoms of Wuchereriasis (Elephant Disease)
Asymptomatic incubation period lasts 3-18 months.
Allergic manifestations may develop approximately 3 months after infection. Microfilariae detected in the blood no earlier than after 9 months. The disease begins with various allergic manifestations. On the skin, especially on the hands, painful elements like exudative erythema appear, lymph nodes increase in the inguinal areas, on the neck and in the armpits, painful lymphangitis, funiculitis, orthoepididymitis, and synovitis with outcome in fibrous ankylosis often occur, and in women – mastitis. With long-term recurrent funiculitis and orchepididymitis occurs hydrocele. Fever is characteristic, bronchial asthma and bronchopneumonia are often developed. After 2-7 years after infection, the disease enters the second stage, which is characterized mainly by lesions of the cutaneous and deep lymphatic vessels with the development of varicose dilatation, impaired lymph flow, and rupture of these vessels. There are painful lymphangitis with regional lymphadenitis. At this time, for several days, the patient has marked symptoms of general intoxication due to high body temperature and severe headaches. Often there is vomiting, sometimes delirious state develops. The attack usually ends with profuse sweating. As a result of ruptures of the lymphatic vessels, lymph flow and a decrease in the intensity of lymphadenitis are observed.
Phases of relative well-being are periodically replaced by regular exacerbations of the disease. In place of lymphangitis there are dense yarns, the affected lymph nodes are also subjected to fibrous compaction. Characteristic is an increase in the inguinal and femoral lymph nodes. Initial swelling of the lymph nodes does not cause pain, however, with the subsequent development of lymphangitis, severe pain appears in the nodes. The lesion can be one- or two-sided, the size of the nodes from small to 5-7 cm in diameter. Often, the so-called lymphoscultum (chylous soaking of tunica vaginalis) and chyluria develop in parallel. Lymphocrotum is clinically manifested by an increase in the scrotum. When palpation of the skin of the scrotum, dilated lymphatic vessels are easily detected. When these vessels rupture a large amount of rapidly coagulating lymph flows. Lymphatic leakage from damaged vessels may last for several hours.
In countries of North Africa, India and China, patients with wucheriasis often have chyluria or lymphuria. The patient notices that the urine has acquired a milky white hue. In some cases, the urine becomes pink or even red, sometimes it is white in the morning and red in the evening or vice versa. The presence of blood in the urine along with lymph is apparently explained by the ruptures of the small blood vessels of the dilated lymphatic vessels. Microfilariae are detected in the urine only at night. Sometimes this is preceded by a slight pain over the pubis or in the groin areas. A characteristic is the retention of urine due to coagulation of the lymph and the formation of flakes in the urinary tract. In lymphuria in the urine there is an admixture of lymph, protein in a significant amount, possible admixture of blood, but there is no trace of fat. Lymphocytes are found in urine sediment.
The bodies of the dead filarial usually dissolve or calcine without a trace. However, in some cases, dead parasites cause the development of abscesses, which lead to severe complications, such as empyema, peritonitis, purulent inflammation of the genitals.
In connection with damage to the walls of the lymphatic vessels in wuchereria, microbes can enter the surrounding tissues and blood, which can lead to the development of sepsis. In the blood of such patients hemolytic streptococcus is often detected.
The third (obstructive) stage of the disease is characterized by elephantiness. In 95% of cases, ivory of the lower extremities develops, more rarely – the upper extremities, genitals, certain parts of the body and very rarely the face. Clinically, elephantiasis is manifested by rapidly progressing lymphangitis with the addition of dermatitis, cellulitis in combination with fever, which in some cases may be the main symptom of the disease and is a consequence of the addition of a bacterial infection. The skin over time becomes covered with warty and papillomatous growths, there are patches of eczema-like skin changes, non-healing ulcers. The legs can reach enormous sizes, they take the form of shapeless lumps with thick transverse folds of the affected skin. The weight of the scrotum is usually 4-9 kg, and in some cases up to 20 kg, a case is described when the patient’s scrotum weight reached 102 kg. In the case of facial elephantiness, the upper eyelid is more often affected.
Diagnosis of Wuchereriasis (Elephant Disease)
The diagnosis and differential diagnosis of wucarariosis is based on epidemiological data and the characteristic clinical picture of the disease (allergic manifestations in the early stage of the disease, damage to the lymphatic system, and finally the development of elephantiasis in the third stage of the disease).
The final confirmation of the diagnosis is the detection of microfilariae in the blood. Blood for analysis must be taken at night. If W. Pacifica invasion is suspected, it is better to take blood for analysis during the day (daytime peak of filariamia). When viewed under a cover glass of a fresh drop of blood at low magnification of the microscope, mobile microfilariae are easily detected. To establish the type of microfilariae, blood products (smears or drops) stained according to Romanovsky are examined. In the third stage of the disease, the concentration of microfilariae in the blood is negligible. In these cases, enrichment methods are used (Bell filtration or concentration). One ml of venous blood is added to 9 ml of a 2% formalin solution in distilled water, the mixture is centrifuged for 3-5 minutes, and the resulting precipitate is examined under a microscope. Used and more complex methods of enrichment. In Hiluria, microfilariae can sometimes be detected in the urine. Intradermal allergy test with antigen from Dirofilariaimitis (dog filarias), complement fixation reaction and agglutination reaction with adsorbed antigens are not strictly specific.
Tests using PCR and immunological tests have also been developed.
Treatment of Wuchereriasis (Elephant Disease)
Albendazole, a broad-spectrum anthelmintic drug combined with ivermectin, is recommended for the treatment of wuchereriasis (elimination of mature stages) outside the United States. The combination of albendazole and diethylcarbamazine is also effective.
Since 2003, the antibiotic doxacycline, which kills bacteria of the genus Wolbachia, symbiotic filarias, is used for the treatment of wucarariosis, which leads to their death or reduction of pathogenicity.
Prevention of Wuchereriasis (Elephant Disease)
Prevention is reduced to the improvement of the population (screening and deilmintization) and vector control.