Studies on Vectors of Onchocerciasis, Simulium Species, in Achi, Oji River Local Government Area, Enugu State, Nigeria

Abstract

The vectors of Onchocerciasis Simulium, flies were studied in Achi, Oji River Local Government Area, Enugu State, Nigeria, to determine the breeding sites, distribution, the vectorial capacity, parous and nulliparous rates, as well as the infection rate, the transmission potentials and the species spectrum of the flies, with a view to recommending some feasible and applicable control measures for the vectors. This would complement or form a component of the chemotherapeutic control of this disease by the use of the drug, Ivermectin. The breeding sites of S. damnosum s.l complex – the vectors – were located around the waterfalls and rapids along the courses of some rivers in Achi, like Oji river, Iyi Nwankpu and Ubeneji. Larval forms were collected by ice collecting method from the substrates in bijou bottles containing carnoy fixative with entomological forceps, for cytotaxonomic studies. The adult flies were collected in collecting tubes on human baits, for morphological identification , parous and nulliparous as well as infection rate studies. They were counted and recorded as daily, monthly and. annual biting rates and also vectorial density or capacity. Total flies caught were 3,135 in one year period, in which 1,527 (70%) were parous and 632 (30%) nulliparous. The Annual biting rate were 4,635, the infected flies were 40 (1.7%). The Annual transmission potential was 25.78. Some Simulium species identified were S. damnosum s. s., S. squamosum, S. yahense and S. sirbanum. Integrated vector control (IVC) is recommended by the use of good chemical larvicide like Temophos, and a mopping up with the biological use of Bacillus thuringiensis, to complement the present control programme using the efficient drug, Ivermectin