Onchocerciasis (River Blindness)

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Onchocerciasis is a tissue parasitic infestation caused by a filarial worm, Onchocerca volvulus. The microfilariae invade lymphatic system, subcutaneous and deep tissues producing acute inflammation and chronic inflammation at a later stage.

Clinical presentation

  • Skin inflammation with papules
  • Subcutaneous nodules
  • Atypical skin lesions (scarred, saggy, hanging areas of skin, leopard skin)
  • Skin nodules under the bony prominent areas
  • Microfilaria in anterior chamber
  • Scleritis and keratitis leading to impaired vision as well as blindness

Investigations

  • Visual acuity
  • Rapid diagnostic test (OV-16 - Onchocerciasis IgG)
  • Skin snip for microscopic examination
  • Slit lamp eye examination
  • B Scan

Pharmacological Treatment

Treatment is done in consultation with dermatologists and infectious disease specialists.

Apart from WHO recommended mass treatment campaign to communities at risk with annual preventive chemotherapy which polarize/paralyze the worm, treatment depends on individual patient presentation.

A: ivermectin (PO) 0.15mg/kg once every 12months for 12–15years

Note:

  • Patients with heavy ocular infestation require retreatment every 3 to 6 months.
  • Treatment will only arrest progression of the clinical features but not reverse them.

Dosage guidelines based on body weight 

Weight 

Dosage 

15-25kg

3mg 

26-44 kg

6mg 

45 -64 kg 

9mg 

65- 84 kg

12mg 

85kg or more 

0.15mg/kg 

Surgical treatment 

Nodulectomy: It is done mostly for nodules located in the scalp to minimize the ocular complications