Emergence and genetic diversity of zoonotic Onchocerca species among human populations in Taraba State, Nigeria

Abstract

In the present study, the genetic diversity of Onchocerca (O.) species was investigated by amplifying a fragment of the 16S rRNA gene from the parasite obtained in some endemic areas in Taraba State, Nigeria. Three local government areas were selected: two onchocerciasis-endemic and one non-onchocerciasis-endemic regions. A total of 211 skin snips using a sterile sclera punch were obtained from consenting participants, males and females residing within the areas for at least ten years or since birth, by convenience sampling methods. The emerged microfilariae were examined microscopically. Nine microfilaria-positive skin snips were identified and preserved in RNALater®. DNA was extracted from recovered microfilariae and residual skin snip specimens and was tested by standard Polymerase Chain Reaction (PCR) using primers targeting the 16S gene. Six PCR-positive samples were sequenced and analyzed. Two sequences varied with those from other regions, suggesting a likely diversity of O. volvulus populations in the study area. A novel finding of O. ochengi, the pathogenic cattle parasite, was identified in some samples, suggesting a potential zoonotic species in humans. Further investigation on the extent of emerging zoonotic onchocerciasis by O. ochengi in the light of cattle, Simulium vectors (blackflies), and environmental and human overlap in the study area is required.