Genetic diversity among natural populations of Schistosoma haematobium might contribute to inconsistent virulence and diverse clinical outcomes

Abstract

There is an evident difference in the intensity of morbidity caused by Schistosoma haematobium in North-African zones compared to Sub-Saharan ones. Clinical outcome dichotomy corresponds to two geographically distinct intermediate host snail species that are only infected by the related strain of the parasite. In concert, there is a manifest hybridization of the parasite with other Schistosoma species confined to certain regions of Africa. This raises a reasonable suggestion that S. haematobium has no less than two phylogenetic clusters that have different virulence. The aim of the study was to examine the possible diversity among S. haematobium using simultaneous amplification of genomic DNA of selected isolates. Random amplified polymorphic DNA-polymerase chain reaction markers were used to study the genetic diversity among S. haematobium natural isolates from selected regions of Africa (Egypt, Zimbabwe, and South Africa) that represent different ecological conditions, different species of intermediate host, and different possibilities of field hybridization with other schistosomes. A moderate to high level of genetic diversity was evident among the three isolates. More bands were shared by the isolates from Zimbabwe and South Africa (similarity index = 0.721) than those shared by each with the Egyptian isolate (similarity index = 0.551 and 0.566, respectively), suggesting that at least two phylogenetic groups of S. haematobium do exist in distinct geographic regions of Africa. The elucidation of the possible genetic diversity among S. haematobium parasites may explain many ambiguous aspects of the biology of the parasite-like virulence, immune evasion and drug resistance.

<p>Genetic Diversity of <em>Schistosoma haematobium</em> in Qena Governorate, Upper Egypt</p>

“…Findings exhibited moderate to high variation in genomic schistosome populations, thus clarifying genetic diversity among S. haematobium populations in Egypt relative to other African isolates from Zimbabwe and South Africa. 46 Our results exhibited high genetic diversity among human isolates in four neighboring geographical regions in Qena Governorate, Upper Egypt. These results are in harmony with those of previous studies that document a high degree of genetic variation in selected S. haematobium populations.…”

“…High genetic diversity may also contribute to the emergence of new strains that are either non-susceptible or drug-resistant through genetic swapping and recombination between old and newly emerged genotypes. 27,44 This 46 In the present research, four RAPD markers A02, A07, A09, and A10 were tested against genomic DNA isolated from 50 S. haematobium egg samples. These primers proved to be useful in differentiating S. haematobium from other schistosomes.…”

“… 45 A previous study in Egypt used RAPD-PCR analysis for natural S. haematobium populations to analyze the genetic diversity of Egyptian isolates as opposed to other African isolates. 46 …”

Diverging patterns of introgression from Schistosoma bovis across S. haematobium African lineages

“…Such diverse introgression patterns could explain some variations in virulence and compatibility with snails in S . haematobium natural populations [ 49 , 50 ]. We advocate that more genomic analyses are thus required to quantify such heterogeneity in introgression patterns and validate the hypothetical link between introgression patterns and these important life-history traits.…”

Schistosomiasis Morbidity Hotspots: Roles of the Human Host, the Parasite and Their Interface in the Development of Severe Morbidity

“…The role of intra-specific differences and interactions on the host morbidity profile must also be considered ( 132 , 133 ). Although the role of the parasite genetic diversity in differential host response is well known for microparasites ( 134 , 135 ), there is comparably less known regarding the potential importance of macroparasite genetic heterogeneities in general, and schistosomes in particular, on disease epidemiology ( 136 ).…”