Onchocercosis - epidemiology, clinics, diagnostics, treatment.
Filariasis
Wuchereriasis - epidemiology, clinics, diagnostics, treatment.
Wuchereriasis is transmissible tissue tropical helminthiasis with mainly impairment of the lymphatic system. It is wide-spread in Africa, Pacific region, China, India, Indonesia.
Causative organism is dioecious nematode Wuchereria bancrofti having length up to 100 mm, the larva has regular flexures of the body, cover.
Epidemiology. A source of invasion and final owner is a man, intermediate owners are mosquitos Culex, Anopheles, Aedes, Mansoni. The periodic form with night peak of microfilariae’s number in a blood and subperiodic day form.
The way of transmission is transmissible during a bite of a mosquito.
Development cycle in a carrier of the disease is: a mosquito swallows larvas (microfilariae) during blood sucking of a sick person => the growth in a mosquito organism => two moults => invased larvae are accumulated in the thrust device of a mosquito in 2-3 weeks.
Development cycle in an organism of a man is: larvae take root in a skin during a bite of a mosquito => larvae penetrate into a blood and reach lymph nodes and vessels => larvae turn into puberal heminths (macrofilariae) which give birth to larvae (microfilariae) => circulation of them in a blood. Microfilariae live 70 days, macrofilariae live more than 10 years.
Pathogenesis includes:
1) sensibilization of an organism by antigens of a helminth;
2) mechanical damage of lymphatic vessels by clews of helminths with the deceleration or the arrest of a flow of the lymph;
3) inflammatory infiltration of walls of lymphatic vessels with a necrosis, subsequent fibrosis and obliteration;
4) increase of lymphonoduses, varicose vasodilatation with their rupture and lymphorrhea in hollow organs, abdominal cavity due to the lymphostasis;
5) an elephantiasis of various parts of a body due to prolonged lymphostasis;
6) an addition of a secondary infection with development of abscesses.
Clinics. Incubative period lasts for 8-16 months.
Early (migratory) stage lasts 2-7 years.
1. Allergic manifestations include rash like an exudative erythema, edemas, itch, high temperature (filariatoid fever), conjunctivitis.
2. Basic manifestation is occasional attacks of a lymphadenitis or lymphangitis with temperature and malaise. Attacks continue about 2 weeks and repeat some times per year during several years.
3. The lesion of lymphatic vessels of sexual organs is combined with a funiculitis, epididymitis, orchitis and leads to the hydrocele.
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4. Mesenteric lymphadenitis is a cause of an acute abdomen.
5. Filarial abscesses in medial fields of the upper parts of thighs are sterile, slowly appear and slowly disappear.
6. The suppuration of lymphonoduses, formation of abscesses and their rupture, formation of ulcers and scars are frequent in Indonesia, Malaysia, Thailand. In India abscesses are rare.
7. Asthmatic bronchitis, pneumonia, eosinophilia may be present.
8. Hepatosplenomegaly.
Stage of a varicose vasodilatation lasts from 2 till 8 years:
1. Sharp increase of lymphonoduses is accompanied by an attack of a pain (blockade by a tangle of parasites with a distention of a capsule).
2. Varicose dilation of superficial and deep lymphatic vessels leads to a lymphostasis.
3. Rupture of lymphonoduses leads: to chyluria and hematochyluria in kidneys and urinary bladder; to chylos diarrhea in an intestine; to chylous ascites in peritoneum; to chylocele in a srotum. A lymphoscrotum is an increase of a scrotum and extention of lymphatic vessels in a combination with the increase of inguinal and femoral lymphonoduses.
4. There are aseptic abscesses around the adult helminths in subcutaneous fat, muscles, genital organs, cavities of joints, thoracic and abdominal cavities. Peritonitis and empyema occur in the appearance of secondary flora.
The third stage (obstructive) lasts more than 8 years:
1. An edema of sheaths of a testicle (hydrocele) with possible hemorrhages, turning into a solid fibrous mass and abscess formation occurs more often in eastern and western regions of tropical Africa and in northern India.
2. Lymphatic edema and elephantiasis more often affect the calfs, scrotum, forearm, penis, female sexual organs, mammae.
3. Chyluria meets less often and can happen with hematochyluria.
4. An elephantic fever results from an addition of secondary flora.
The occult filariasis is characterised by absence of clinics and microfilariemia, immunological hypersensitivity, discharge of microfilariae by the lungs (clinics of a bronchopneumonia with an eosinophilia).
Differential diagnostics: malaria, brucellosis, tuberculosis, HIV-infection (AIDS).
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Laboratory diagnostics.
1. There is the microscopy of a native blood smear taken in the afternoon and in the night for detection of microfilariae (it is necessary to investigate urine, chylous fluid).
2. The microscopy of stained smears and thick drops of the blood determines species with a quantitative evaluation.
3. The method of concentration on membranous filters with colouring and microscopy is used at the low level of microfilariaemia.
4. Mazotti’s test is an increase of microfilariae in a blood in 15 minutes after prescription of 100 mg of ditrasine.
5. The immunological methods (Complement Fixation Test, Indirect Haemagglutination Test, Reaction of fluorescent Antibodies) have a secondary importance.
Treatment.
Diaetylcarbamazine citras (Ditrazin citras, Banocid, DEC) 4-6 mg/kg/day PO after meals for 14-21 days. The courses are repeated.
An antibacterial therapy is prescribed in elephantic fever.
There is surgical treatment in the late stages (chyluria, elephantiasis, hydrocele).
Onchocercosis - epidemiology, clinics, diagnostics, treatment.
Onchocercosis (River blindness) is transmissible tropical tissue helminthiasis with mainly impairment of the skin, hypodermic fat, lymph nodes and eyes. It is wide-spread in tropical Africa, Mexico, Colombia, Guatemala.
Causative factor is Onchocerca volvulus dioecious nematode having length up to 100 mm, the larva has angular flexures of a body and has no cover.
Epidemiology. A source of an invasion and final owner is a man, intermediate owners and transmitting organisms are midges of Simulium species, which multiply in fast flowing rivers (foci near the rivers). Two types of Onchocerca are distinguished in Africa: that of dampforest and that of savanna (it is more virulent and more often results in blindness). Hunters, fishermen, workers of coffee plantations form risk group. The way of transmission is transmissible.
Development cycle in a carrier of the disease consist of following: the midges swallow microfilariae during blood sucking => microfilariae develop up to invasive stage in 6-7 days.
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Development cycle in an organism of a man is: larvae take root into a skin during a bite of the midges and penetrate into a blood => they get under a skin and aponeuroses of the muscles => they become puberal => female gives birth to larvae (microfilariae) up to 2 millions per year => microfilariae are accumulated in a skin, lymphonoduses, tissues of an eye.
Pathogenesis.
1. Toxico-allergic influence of the puberal parasites and larvae leads to the development of allergic immediate and slow type reactions.
2. Mechanical influence of adult parasites, formation of the granulomatous reaction with a fibrosis around them causes the connective tissue noduses “onchocercomae”.
3. The penetration of microfilariae into an eyeglobe results in an impairment of the posterior and anterior chambers, a sclerosis, an atrophy of an optic nerve and blindness.
4. The dermatitises, lymphatic oedema of the skin, sexual organs, extremities develop due to the parasitizing there.
Clinics. Incubative period lasts till one year.
1. Local edema on a place of a bite, itch, urticarious rash, eosinophilia.
2. Onchocercal dermatitis is characterised by a strong itch, erythematic - papular rashes (“filariatosous scabies”), hyperpigmentation then hypopigmentation, cutaneous oedema, dryness, peeling, atrophy. Pseudoadenocysts (“a pendent groin”, “a pendent armpit”) with hypodermic tissues and lymphonoduses occur.
3. Onchocercomae - the dense, mobile, painless noduses from 0,5 to 10 cm with thin-walled or dense connective tissue capsule, with alive or dead parasites - are situated in Africans below waist, in the Americans on the top part of a body. They can suppurate or calcinate.
4. The impairment of lymphatic system leads to the inguinal and axillary lymphadenitis, oedemas, orchitis, hydrocele, elephantiasis of the lower extremities and genitals.
5. The impairment of the eyes runs as the conjunctive-corneal syndrome, punctated keratitis, ulcer of the cornea, sclerosis of the choroidal vessels, neuritis and atrophy of the optic nerve, blindness.
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