Onchocerciasis

Question 1

What causes Onchocerciasis, and how is it transmitted?

Answer 1

Onchocerciasis, or river blindness, is caused by the filaria Onchocerca volvulus. It is transmitted by female blackflies, which are typically found near fast-moving water.

Question 2

What are the primary symptoms of Onchocerciasis in the skin?

Answer 2

Symptoms include severe itching, erythematous hyperpigmented papules, scratch marks, thickened and lichenified skin, loss of skin elasticity (hanging groins), and skin hyper-, hypo-, and depigmentation in chronic cases.

Question 3

What are onchonodules, and where are they commonly found?

Answer 3

Onchonodules are subcutaneous nodules representing adult worms, commonly found above the hipbones but can also be present elsewhere

Question 4

How can Onchocerciasis be diagnosed if microfilariae are not demonstrated?

Answer 4

If the history is suspect but microfilariae are not demonstrated, a Mazotti test can be performed. This involves giving 50-100 mg of diethylcarbamazine (DEC, Hetrazan) under careful conditions, as a positive test yields intolerable itching within a few hours

Question 5

What is the primary treatment for Onchocerciasis?

Answer 5

Ivermectin is the primary treatment, killing microfilariae with a single oral dose. Repeated treatment every 3 to 12 months is necessary if the patient stays in an endemic area. If the patient moves out of the area, repeated treatment may cure the infection as the adult worms die after a few years.

Question 6

How should Onchocerciasis be managed if there is eye involvement?

Answer 6

When there is eye involvement, steroid treatment should precede ivermectin.

Question 7

What is the dosage of ivermectin for treating Onchocerciasis based on body weight?

Answer 7

The dosage of ivermectin is:
Under 30 kg: 0.5 tablet (6 mg tablet)
30 to 50 kg: 1 tablet
50 to 70 kg: 1.5 tablets
Over 70 kg: 2 tablets