Onchocerciasis

Introduction to onchocerciasis Onchocerciasis (onchocerciasis) is a parasitic disease caused by the parasitic silkworm parasitic on the eye or subcutaneous tissue. The main clinical feature is eye damage, which can cause blindness. It is also called river blindness. . basic knowledge Sickness ratio: 0.0001% Susceptible people: no special people Mode of transmission: black fly transmission Complications: dwarfism, femoral hernia, glaucoma, optic atrophy

The cause of onchocerciasis

(1) Causes of the disease

Adults are linear, white, tapered and obtuse at both ends. Females are 33.5 to 50 mm long and 0.27 to 0.40 mm wide. Males are 19 to 42 mm long and 0.13 to 0.21 mm wide. Microfilariae are highly active and have no sheath. There are two kinds of microfilaments, the length of which is large, and the width is (285 ~ 368) m × (6 ~ 9) m; the length is small, the width is (150 ~ 287) m × (5 ~ 7) m, very It is rare in peripheral blood. It is mainly found in the connective tissue near the female and the lymphatic vessels in the skin. It can also be seen in the eye tissue and urine. It is not obvious in periodicity and can survive for about 30 months. When the intermediate host is a Simulium When not only sucking blood and sucking the skin tissue fluid, the microfilaria is swallowed with the tissue fluid and reaches the pectoral muscle. After about 6 to 7 days, it develops into the infected larvae and migrates to the lower lip of the sputum. That is, the human body is infected, the larva develops into an adult for about 1 year, and the adult life span does not exceed 18 years, generally 8 to 10 years.

(two) pathogenesis

Adults and microfilariae have pathogenic effects. Adults are parasitic in the subcutaneous tissue lymphatic junction. The most basic lesions of this disease occur in the skin, lymph nodes and ocular tissues. In the skin, it is characterized by mild chronic inflammation and late elastic fibers. Reduced, atrophic and fibrotic, can form subcutaneous fibrous nodules, adultia in the nodules, pathological examination found granuloma around the worm, fibrous tissue and eosinophils, giant cells, plasma cells, etc., lymph node lesions Chronic inflammatory changes, ocular tissue often has chronic non-granulomatous inflammatory changes, microfilaria can cause punctate keratitis or corneal opacity, iritis or iridocyclitis, choroidal retinitis, optic atrophy, Leading to blindness.

Onchocerciasis prevention

In the immune zone, since the disease is transmitted by black flies, the elimination of black flies has become an important aspect of controlling this disease.

Onchocerciasis complications Complications, dwarfism, hernia, glaucoma, optic atrophy

Dwarfism, femoral hernia, glaucoma, optic atrophy, etc.

Onchocerciasis symptoms common symptoms itching itch nodules corneal opacity

The incubation period is unknown. It can be found that infants under 1 year old can be diagnosed with adult nodules. It is estimated that the adult and microfilariae have a pathogenic effect on humans, especially in the latter.

1. Skin damage: Adults parasitize the lymphatic confluence in the subcutaneous tissue, causing local inflammatory reaction, fibrous tissue hyperplasia, forming fibrous nodules surrounding the worm body, nodules diameter 2 ~ 25mm, or larger, no pain Hard, it contains two to several adult and many microfilarias, the number of nodules is more than 3 to 6, and there are also hundreds of people, can be found in any part of the body, microfilariae metabolites or Toxic substances after death can cause skin allergic reactions and can cause severe dermatitis. The rash can occur in the face, neck, shoulders, etc. It is itchy, accompanied by hyperpigmentation, showing pigmentation areas or pigmentation disappearance areas, and looks like a leopard. Skin, it is also known as leopardosis, followed by skin thickening, discoloration, cracking, and finally the skin loses its elasticity and shrinks like an old man.

2. Lymph node lesions: lymph nodes can be swollen, firm and painless, containing microfilariae. In some parts of Africa, some patients have a "hanging groin", which is the loss of elasticity of the skin causing the groin to sag. Forming a drooping sac containing enlarged fibrotic lymph nodes, in addition, can cause scrotal hydrocele, external genital elephantiasis, hernia (especially femoral hernia).

3. Eye damage: the most serious, this is the microfilariae from the adjacent tissue into the eye, the mechanical damage of the microfilaria, the secretion of microfilariae or the antigenic substance and toxic substances after death cause the eye Damage, development is slow, eye damage in some areas of Africa is as high as 30% to 50%, microfilariae invade the cornea, can cause corneal opacity, affect vision, severe fibrosis, can cause blindness, microfilaria can be Free movement in the eye can also invade the deep part of the eye, causing inflammation of the iris, ciliary body, retina and choroid, or partial or total blindness caused by invasion of the optic nerve. Adults suffering from "river blindness" can reach 5% to 20%.

4. Dwarfism: Dwarfism caused by microfilariae directly or indirectly damage the pituitary gland in Uganda.

Inspection of onchocerciasis

From the tumor puncture, or with a skin-like biopsy clip, take a small amount of epidermis on a glass slide and add physiological saline for biopsy to see microfilaria. In addition, microfilaria can be found in urine and blood. The immunodiagnostic method has little practical significance and needs further study.

Slit lamp, ophthalmoscope directly to see the microfilaria in the anterior chamber of the eye, or surgical removal of the subcutaneous nodules to find adults.

Diagnosis and identification of onchocerciasis

The diagnosis of this disease is mainly based on the area in which the patient lives and the typical eye changes. Patients in the non-epidemic areas have recently visited African or South American infected areas, and have asymmetric itching, acute rash and limb swelling. Suspected onchox filariasis, and detailed clinical examination and laboratory examination, microfilaria in the cornea and aqueous humor for the diagnosis of diagnosis, microfilaria in the skin specimens can also be confirmed, with radioimmunoassay Enzyme-linked immunosorbent assay for the determination of specific antibodies can be helpful in the diagnosis.

Acne and dermatitis are common irritating skin lesions in the tropics and need to be differentiated from this disease.

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