Author Contributions
AEB, IM and JK identified the research problem and designed the research project, MO-K, PS, IF, M, JK and LJR co-ordinated the field studies and molecular epidemiology, CK, DL-N, CB processed samples and performed molecular assays, JHK, ZR, RK and AAF conducted the microsatellite genotyping and analysed data, CJ and CK contributed data, JHK and AEB wrote the paper.