What Is River Blindness?

Onchocerciasis is a parasitic disease characterized by moss-like dermatitis, subcutaneous nodules, and visual impairment caused by onchocerciasis parasitizing human skin, subcutaneous tissue, and eyes. It is also called river blindness or blind filariasis. It is widespread in Africa and tropical America, and can cause 5% to 20% of adult blindness in endemic areas. The media is .

Basic Information

nickname: River blindness or blind filariasis
Visiting department: dermatology
Multiple groups: African and Tropical Americans
Common locations: Skin, lymph nodes and eyes

Common causes: Spinosaurus parasitizes on human skin, subcutaneous tissue, and eyes
Common symptoms: A rash on the face, neck, shoulders and other areas, itching at first, and eventually forming patches with marginal pigmentation and central hypopigmentation. Lymph nodes can swell, vision loss, blindness, etc.

Causes of Onchocerciasis

Male and female adults of Onchocerca spp. Are often paired or kinked into clumps, parasitizing human subcutaneous tissue, and the females produce microfilariae after fertilization. Whenever a female cricket bites a person to suck blood, the microfilariae enters the sac of the tadpole with the tissue, passes through the midgut, reaches the pectoral muscle through the blood cavity, and develops into an infected larva after two molting and moves to the lower lip of the tadpole. When the pupa bites again, the larva escapes from the lower lip and enters the human skin to become infected. Adults and microfilariae have pathogenic effects on humans, especially the latter. Adults parasitize the confluence of lymphatic vessels in the subcutaneous tissue, locally causing an inflammatory response, fibrous tissue hyperplasia, and forming fibrous nodules surrounding the body. In addition to parasitic in the connective tissue near the adult, microfilariae can also migrate to the skin, subcutaneous tissue, skin lymphatics and eyeballs in other parts. Microfilaments can invade the eyes and can cause vision impairment and blindness.

Clinical manifestations of onchocerciasis

Clinical symptoms appear during the incubation period of 3 to 15 months after infection, and are mainly limited to the skin, lymph nodes, and eyes.

Skin damage

Adults parasitize the confluence of lymphatic vessels in the subcutaneous tissue, locally causing inflammatory reactions, fibrous tissue proliferation, and forming fibrous nodules surrounding the worm. The nodules are 2 to 25 mm in diameter, or larger, painless and hard. Contains two to several adults and many microfilaria. The number of nodules is mostly 3 to 6, and there are also hundreds of them, which can be seen in any part of the body. Metabolites of microfilaria or its toxic substances after death can cause skin allergic reactions and can cause severe dermatitis. The rash can occur on the face, neck, shoulders, etc., and itchy at first, and eventually forms a patch of marginal pigmentation and central hypopigmentation, which looks like leopard skin, so it is also called leopard skin disease. Following the thickening of the skin and discoloration, the skin loses its elasticity and shrinks like an old man.

2. Lymph node lesions

Lymph nodes can be swollen, solid, painless, and contain microfilaria, a characteristic feature of onchocerciasis. In addition, it can still cause scrotal effusion, external genital elephantiasis, hernia (especially femoral hernia).

3. Eye damage

It is the most serious lesion of onchocerciasis. This line of microfilariae enters the eye from nearby tissues. It is caused by mechanical damage of live microfilariae, secretions of microfilariae, or antigenic and toxic substances after death. Eye damage develops slowly, and most patients are over 40 years old. Microfilariae enter the cornea from the skin through the conjunctiva, or enter the back of the eye through the bloodstream or the ciliary body blood vessels and nerve sheaths. After microfilament death, it causes inflammation, resulting in corneal damage and corneal cloudiness. Causes iris, ciliary body, retina and choroid inflammation or invades the optic nerve, affects vision, severe cases of fibrosis, can cause blindness.

Onchocerciasis examination

1. Peripheral blood eosinophils and IgE increased.

2. Take a small amount of epidermis from the puncture solution of the mass, or use a skin-like biopsy clip, and see the microfilament in the anterior chamber with a slit lamp or ophthalmoscope; or remove the subcutaneous knot by surgery Adults were found in the section.

Onchocerciasis diagnosis

According to the typical clinical manifestations in the epidemic area, take a small amount of epidermis from a biopsy fluid or a skin-like biopsy clip and place it on a glass slide and add physiological saline for biopsy. A diagnosis can be established by seeing the microfilariae in the anterior chamber of the eye, or by detecting the adult worm in the subcutaneous nodule surgically removed. In addition, microfilament puppets can be found in urine and blood. The accuracy of immunofluorescence and ELISA tests can reach 60% to 90%, and further research is needed. In the onchocercia genome, a 150kb gene series is unique to the species of onchocerciasis. The use of PCR to amplify this gene has important value in the diagnosis of onchocerciasis.

Differential diagnosis of onchocerciasis

Scabies and ringworm are common irritating skin lesions in the tropics and need to be distinguished from onchocerciasis.

Onchocerciasis treatment

Except for Hai Qunsheng and Suramin, ivermectin is superior to Hai Qunsheng in terms of safety, tolerance, and efficacy. Taking ivermectin can significantly reduce the number of microfilariae in the skin, and its side effects are lighter than that of the sea group.

Ivermectin

This product has no effect on adults, but has a strong effect on microfilariae and microfilariae embryos that are developing in the uterus. It is taken once a year or once every six months. Almost all the microfilariae disappeared within 1 month after taking the medicine once, and maintained a low density. After half a year, the number of microfilariae gradually increased. Therefore, 1 / year treatment is needed in endemic areas.

2. Ethylazine (Hai Qunsheng)

The effect is good, but the side effects are large, and it can be used as a medicine for those who cannot use ivermectin.

3. Suramin Sodium (Suramin)

Although this product can kill adult worms, it is highly toxic and cannot be used routinely except in a few cases.

Onchocerciasis prevention

Census treatment of patients and elimination of the media are the key to preventing the disease. In endemic areas of the disease, you should try to avoid being bitten by mosquitoes and black flies.