Onchocercosis
Description:
Onchocercosis - chronically proceeding filariasis which is characterized by preferential damage of skin, hypodermic cellulose and eyes.
The onchocercosis is widespread in forest areas along the rivers and streams. The onchocercosis is eurysynusic in a number of the countries of Africa, the centers of an onchocercosis exist in Brazil, Mexico, Costa Rica, Venezuela, Guatemala. Around the world about 13 million people suffer from it.
The onchocercosis takes the second place among the infectious reasons of a blindness.
Onchocercosis symptoms:
Nodes become noticeable approximately in 3-4 months after infection. Females are capable to give rise to microfilarias approximately in one year of parasitizing in a human body.
Incubation interval duration - about 1 year. The disease begins with a febricula and fever. Note dryness and a peeling of skin, pruritic papular rash. Sometimes papules are transformed to pustules with formation of ulcers. At a considerable prevalence microfilarias skin takes a form of a lemon crust, shagreen or elephant skin. Eventually there are sites of a depigmentation of skin.
Onkhotserkoma. The most characteristic sign of an onchocercosis is existence under skin of dense, mobile, often painful fibrous nodes the sizes from 1-2 to 5-7 cm. Nodes can be on various body parts, but meet on the head, in pelvic area and around joints more often. In Africa at patients with an onchocercosis nodes are localized in the field of a basin, is more rare in shovels and are even more rare on the head. Most often they meet over ledges of bones where the hypodermic fatty tissue is thinner. Carriers of S. damnosum, S. neavei generally attack the lower body parts while in Central America the carrier of S. ochraceum attacks the head and a neck. In South America nodes at patients are located in occipital and temporal areas more often.
Changes of skin are one of characteristic symptoms of an onchocercosis. Skin becomes firm, shrivels, shelled, melkopapulezny, strongly pruritic rash periodically develops. Body temperature at the same time increases, symptoms of the general intoxication (the general weakness, headaches) appear. On papules then there are bubbles or pustules which ulcerate afterwards. Ulcers heal slowly with formation of hems. Quite often arising dermatitis very reminds an erysipelatous inflammation of skin. In these cases skin on affected areas becomes edematous, dark red color, body temperature reaches 39-40 °, hypostasis of lips and auricles develops. Exacerbations of dermatitis duration from several days to several weeks gradually lead to the fact that skin on the struck places is thickened, becomes edematous, increase in auricles is noted, they are bent kpered. On a neck and a back sites of the depigmented skin appear.
In certain cases (generally it concerns to Europeans) fibrous nodes are not formed though it is possible to find a huge number of parasites in skin. At this disease elephantiasis of a scrotum, the lower extremities, persons, to the gidrotsela, an orchitis, the localized abscesses, arthritises, perforation of bones of a skull causing epileptiform spasms are described. In the started cases patients with an onchocercosis of men sometimes have skin bags in which there are increased sclerosed femoral or inguinal lymph nodes.
Damage of eyes. At hit of microfilarias in an eye there are symptoms of chronic conjunctivitis, mucous is thickened, especially in the place of transition of a cornea to a sclera where the roller of a hyperemic conjunctiva 2-3 mm thick is formed. A precursory objective symptom of damage of a cornea is emergence of small gray-white spots in blankets. In this period of a disease photophobia, dacryagogue, a nictitating spasm develop. Defeats gradually extend from the periphery to the center of a cornea, causing permanent opacification it with a sharp vision disorder. The pannus at an onchocercosis often has triangular shape with the basis on the periphery and top at the center of a pupil. The iris of the eye often is depigmented and atrophies. In an anterior chamber of an eye exudate of brown color comes to light. Heavy eye complications of an onchocercosis are the cataract, glaucoma, a chorioretinitis and an atrophy of an optic nerve.
Damage of lymph nodes. Easy or moderate increase in lymph nodes - especially superficial and deep inguinal is often observed. By gravity in a groin the hanging-down skin pockets in which the increased lymph nodes are displaced are formed. It increases risk of inguinal and femoral hernias.
Other manifestations. At a heavy invasion the cachexia with loss of fatty tissue and an atrophy of muscles sometimes develops.
Among the adults who lost sight, mortality by 3-4 times exceeds usual.
Onchocercosis reasons:
It was supposed that there are two types of the onkhotserok capable to cause diseases of people: Lake of volvulus (Africa) and O. of caecutiens Brumpt (South America). Now it is proved that morphologically and biologically these parasites are identical. Onkhotserki have a threadlike body, утончающееся by the ends. Length of a parasite is 19-50 mm, width - 0,13-0,4 mm. Females are larger than males. Microfilarias can be large, 0,29-0,37 x 0,09 mm in size, and small, 0,15-0,29 x 0,05-0,07 mm in size.
A final owner is the person, intermediate owners (disease carriers) - females of midges of the sort Simulium. Adult parasites are localized in the fibrous nodes which are located under skin, an aponeurosis of muscles, a periosteum. Females of a parasite give rise to microfilarias which live mainly in skin blankets, is frequent in eyes, is more rare in lymph nodes and internals and is very rare in blood.
Treatment of the Onchocercosis:
WHO recommends several schemes of therapy of patients with an onchocercosis with the specified means in various combinations. The choice of a method of treatment and self-treatment of patients are carried out by only specially trained doctors that is connected with development of heavy allergic reactions at death of parasites as Mazzoti's reaction, with a possibility of an aggravation of damages of eyes in the course of treatment, and also with toxicity of a number of drugs.
The main tasks - to prevent irreversible changes and to facilitate a condition of the patient. At an arrangement onkhotserky on the head surgical treatment as puberal parasites are in close proximity to eyes is recommended. In other cases the main method of treatment - medicamentous.
Ivermectin, semi-synthetic macrocyclic lactone, is effective concerning microfilarias and serves as choice drug at an onchocercosis. Drug is appointed inside in a dose of 150 mkg/kg by 1-2 times a year. Side effects happen seldom - an itch, urticaria and spotty and papular rash are observed in 1-10% of cases. Ivermectin is contraindicated to children 5 years, pregnant and feeding are younger. It is impossible to apply it and at diseases of TsNS which can promote penetration of ivermectin through a blood-brain barrier (in particular, at meningitis). The single dose of ivermectin considerably reduces quantity of microfilarias, but its action time lasts only 6 months.
Suramin - strong, but toxic antiparasitic drug - is active concerning puberal helminths. It is appointed only if full treatment is necessary. Due to the nephrotoxic action of a suramin during treatment carefully monitor function of kidneys.
