Genetic Diversity of Schistosoma haematobium in Sub-Saharan Africa: A Systematic Review

Urogenital schistosomiasis caused by the parasite Schistosoma haematobium is the most common form of schistosomiasis. This parasite has a high potential for genetic exchange within parasite populations giving rise to the genetic diversity that is important for its survival. Genetic differences may lead to some parasite strains being more immunogenic which may have a negative impact on management and control of schistosomiasis. Therefore, understanding these genetic differences in the parasite may lead to better management of the disease. The aim of this review was to systematically review scientific literature on the genetic diversity and population structuring of S. haematobium and the methods used across sub-Saharan African countries. A literature search was done on PubMed, African Journals online and Google scholar using predefined search terms such as urinary schistosomiasis, S. haematobium, genetic diversity in sub-Saharan Africa in combination with Boolean operators (AND, OR). The search included studies published from 2000-2020 that emphasised on genetic diversity of S. haematobium in sub-Saharan Africa. A country in sub-Saharan Africa was included if had a study that determined the genetic diversity of S. haematobium Sixteen study articles from 18 sub-Saharan African countries met the inclusion criteria The genetic diversity of S. haematobium varied from low to high using different methods. Most studies conducted in these countries showed a high genetic diversity of S. haematobium 18/36 (50%) studies. Four methods namely, restriction fragment length polymorphism, randomly amplified polymorphic DNA, DNA barcoding and Microsatellite markers were used to determine diversity In these studies, measures of genetic diversity such as number of alleles per minute or allelic richness, heterozygosity, number of genotypes and unique haplotypes were used. Microsatellites were the most commonly used method and the studies reported number of alleles per locus ranging from 2-19 alleles per locus and heterozygosity of 6 to 71% in some studies. . The highest number of studies were conducted in West Africa Nigeria and Zimbabwe , 4/36(11%) each. Results show the need for continued monitoring of genetic variations in S. haematobium in sub- Saharan Africa. This will aid in understanding the epidemiology of disease, advancing novel treatment and vaccine strategies.