Ochocerca volvulus and its vector in the South Kavirondo district of Kenya

Abstract

Onchocerciasis is recorded in an area of South Kavirondo. The skin infection rate in a sample of 609 (men, women and children) was 51 per cent. varying from 98 per cent. to 13 per cent. The vector is Simulium neavei which is present in greatest density in areas of highest human infection. The fly infectivity rate for the whole area was 10·1 per cent. Contact between fly and population is made in the vicinity of rivers—in the bush and at fords. S. neavei appears to harbour in the lighter bush bordering rivers. It has been found as far as 700 yards from a stream but occurs in greatest numbers within 300 yards. A survey of the rivers and tributaries produced larvae and pupae of S. lepidum, S. hirsutum, S. alcocki, S. elgonensis, S. nigritarsus, S. duodecimum, S. unicornatum and one S. damnosum, but not that of S. neavei. Attempts to infect various animals by the bite of captured adult S. neavei appear to be unsuccessful.