River blindness is caused by-

Ans. is 'a' i.e., Onchocerca Onchocerciasis (River blindness or Robles disease)o It is caused by Oncocerca volvulus.o Infection in human begins with deposition of infective larvae on skin by the bite of an infected blackfly.o The manifestations are -1) Oiicocercomata: These are subcutaneous itchy nodules over coccyx, sacrum, iliac crest and trachanter of femur. Nodules are firm and nontender.2) Skin: Pruritis & Rash are most frequent manifestation of onchocerciasis.3) Ocular Tissue: Visual impairment is the most serious complication of onchocerciasis.4) Lymph nodes: Mild to moderate lymphadenopathy is seen in inguinal & femoral areaso Definitive diagnosis depends on the detection of an adult worm in an excised nodule or more commonly of microfilariae in skin scrappings.