Genetic Diversity and Emerging Zoonotic Onchocerca Species in Human Populations in Taraba State, Nigeria

Abstract

Background: A better understanding of parasite population genetic processes in specific biogeography is needed to support onchocerciasis elimination goals. The genetic diversity of Onchocerca microfilariae was explored by amplifying a fragment of the 16S rRNA gene in the endemic area in Taraba State, Nigeria, Methods: Eight (8) communities were selected including six onchocerciasis endemic communities with records of ivermectin treatment having been annually distributed for 10 to 16 years, and two non-onchocerciasis endemic areas. The participants were 211 from endemic and 110 from non-endemic areas as control. Skin snips were taken from consenting participants by convenience sampling methods using a sterile sclera punch, from males and females residing within the communities for ten years and above or since birth, microfilaria and residual skin snips were preserved in RNALater® in a 1.5 ml micro-centrifuge tube. DNA was extracted from microfilariae recovered and from those in residual skin snip specimens. Polymerase Chain Reaction (PCR) amplification using specific primers for 16S genes was done to detect the identity of Onchocerca species. The amplified products were sequenced and analyzed for species identity. Results: Multiple sequence alignment and phylogenetic analysis results showed distinct diversity of two sample sequences (G49_O.v. Gashaka and Y02_O.v. Yorro) from other samples from the study area and other regions, indicating emergence of a new polymorphic strain of O. volvulus. Report of a preliminary case of emerging zoonosis of O. ochengi infection in human (skin snips) sample (O. ochengi G44) in this study. Conclusions: It is clear there is genetic diversity of Onchocerca species and emerging zoonosis in the study site. We suggest further investigation on the extent and potentials of emerging zoonotic onchocerciasis by O. ochengi, in the light of cattle, Simulium vectors, environmental and humans overlap in the study area.