Background: Schistosomiasis is a chronic parasitic disease, affecting over 207 million people and causing over 300,000 deaths per year mainly in sub-Saharan Africa. Significant numbers of non-human primates such as Chlorocebus aethiops (Ch. aethiops) (vervet) and Papio anubis (baboon) are naturally infected with S. mansoni in Ethiopia, and may have potentially significant implications for transmission and control efforts.

Objective: The objective of this study was, therefore, to assess the genetic diversity and population structure of S. mansoni isolates from human and non-human primates free ranging in close proximities to villages in selected endemic areas of Ethiopia.

Methods: A cross-sectional study was conducted in Bochesa (Ziway), Bishan Gari (Kime) and Finchaa (Camp 7) endemic localities in Oromia Regional State, Ethiopia. For population genetic study 2,356 S. mansoni miracidia were directly isolated from faecal specimens of 60 human hosts and 44 non-human primates. DNA extraction, PCR amplification, and genotyping were performed using fourteen microsatellite loci.

Result: 201 alleles were scored for 14 loci examined. Individual alleles counted for human and monkey in Bochesa were 137 and 100, for human and baboon in Kime were 103 and 119, and for human and baboon in Finchaa were 152 and 89, respectively. At a population level, the mean number of alleles per locus, allelic richness, expected heterozygosity in Hardy-Weinberg equilibrium and pairwise genetic differentiation (F_ST) values ranged from 6.3-10.9, 4.71-7.38, 0.41-0.55, and 0.19-26.78%, respectively. The Bayesian structure and the FCA showed three clusters of population. Genetic diversity of S. mansoni isolates among and within individual subjects from the three endemic areas at infrapopulation level also showed a value of 2.00-6.93, 1.06-1.93, 34-59% and -0.146-0.236, mean number of alleles per locus, allelic richness, expected heterozygosity in Hardy–Weinberg equilibrium and  inbreeding coefficient (F_IS), respectively.

Conclusion: Occurrence of infection of a single host with multiple S. mansoni strains and inter- and intra-host genetic variations was observed. Substantial genetic diversity and gene flow across S. mansoni population per site occurred and non-human primates likely play a role in local transmission and maintenance of infection. Therefore, public health and wildlife professionals should work together for better disease control and elimination strategies.

Key words: Schistosoma mansoni, Human, Non-human primates, Ch. aethiops, Vervet, Papioanubis, Baboon, Genetic diversity, Population structure, Ethiopia