New insights into the genetic diversity of Schistosoma mansoni and S. haematobiumin Yemen

Abstract

Background: Human schistosomiasis is a neglected tropical disease of great importance that remains highly prevalent in Yemen, especially amongst rural communities. In order to investigate the genetic diversity of human Schistosoma species, a DNA barcoding study was conducted on S. mansoni and S. haematobium in Yemen.

Methods: A cross-sectional study was conducted to collect urine and faecal samples from 400 children from five provinces in Yemen. The samples were examined for the presence of Schistosoma eggs. A partial fragment of the schistosome cox1 mitochondrial gene was analysed from each individual sample to evaluate the genetic diversity of the S. mansoni and S. haematobium infections. The data was also analysed together with previous published cox1 data for S. mansoni and S. haematobium from Africa and the Indian Ocean Islands.

Results: Overall, 31.8 % of participants were found to be excreting schistosome eggs in either the urine or faeces (8.0 % S. mansoni and 22.5 % S. haematobium). Nineteen unique haplotypes of S. mansoni were detected and split into four lineages. Furthermore, nine unique haplotypes of S. haematobium were identified that could be split into two distinct groups.

Conclusion: This study provides novel and interesting insights into the population diversity and structure of S. mansoni and S. haematobium in Yemen. The data adds to our understanding of the evolutionary history and phylogeography of these devastating parasites whilst the genetic information could support the control and monitoring of urogenital and intestinal schistosomiasis in these endemic areas.

Fig. 1

A geographic map showing the location of the districts and provinces involved in the study. The map was created using the Esri ArcMap 10.2.1 software

Fig. 2

Minimum spanning TCS networks incorporating all 19 S. mansoni cox1 haplotypes from Yemen. Each line between haplotypes represents a single bp change and small circles between lines represent unsampled or extinct haplotypes. Group 1: Taiz (YTSM) & Ibb (YISM); Group 2: Sana’a (YSSM) & Dhamar (YDSM); Group 4: Ibb (YISM) Group 5: Ibb (YISM), Hodiedah (YHSM) & Dhamar (YDSM). Grouping of haplotypes was based on Webster et al. [15]

Fig. 3

Minimum spanning TCS networks joining the 19 S. mansoni cox1 Yemeni haplotypes from this study with other haplotypes from 14 countries within sub-Saharan Africa from Webster et al. [15]. Each line between haplotypes represents a single bp change and small circles between lines represent unsampled or extinct haplotypes. Connecting group 6 with group 4 was done based on a connection limit of 20–30 nucleotide differences. Majority of Yemeni isolates were grouped closely to coastal Kenya and Zambia (group 4) while five haplotypes were linked with more complicated network to Niger, Saudi Arabia, Senegal, Mali, Oman, Egypt and Kenya (group 1). Four haplotypes divided equally between Zambia ZA2 (group 5) and central Africa, Cameron, Niger and Nigeria (group 2). Yemeni haplotypes linked African haplotypes with long branches within four groups

Fig. 4

Neighbor-joining cox1 phylogenetic tree for S. mansoni with 1000 bootstrap values. Nineteen haplotypes clustered into five groups

Fig. 5

Minimum spanning TCS networks incorporating all 9 S. haematobium cox1 haplotypes from Yemen. Each line between haplotypes represents a single bp change and small circles between lines represent unsampled or extinct haplotypes. The network forms 2 groups of haplotypes linked together. Group 1 forms one branch containing only samples from Hodiedah (YHSH). Group 2 forms simple network containing Taiz (YTSH), Dhamar (YDSH), Sana’a (YSSH) and Ibb (YISH). The majority of the samples are closely clustered around the main haplotype (Y2TDISH) with separate single links representing a single polymorphic mutation

Fig. 6

Minimum spanning TCS networks joining the 9 S. haematobium cox1 Yemeni haplotypes by this study and 18 countries across Africa and the Indian Ocean Islands from by Webster et al. [15, 22]. Each line between haplotypes represents a single bp change and small circles between lines represent unsampled or extinct haplotypes. H1 involved haplotypes from SE1, SE2a, SE3a, SE4, SE5, SE6a, SE7a, SE8a, SE9, MA2, NI1a, NI2, LB1, GB1, NG1, CA1, CA1a, CA2, CA3, CA4, CA5, SU1, KE2, TA1a, MW1, MW2a, MW3 & Zan4. Hodiedah haplotypes were exclusively linked with group 1 and Y5HSH was found similar to H1. The rest of Yemeni haplotypes were grouped with coastal Kenya, Zanzibar, Tanzania, Mauritius & Madagascar. Y2TDISH include Y2DSH, Y2TSH & Y2ISH haplotypes (group 2). Yemeni haplotypes linked the two groups of African haplotypes with small branches

Fig. 7

Neighbor-joining phylogenetic tree for S. haematobium with 1000 bootstrap values. Y2TDISH was the dominant haplotype detected in three provinces, Taiz (Y2TSH), Dhamar (Y2DSH), and Ibb (Y2ISH)