Abstract for presentation at 11th International Congress of Human Genetics

Frequency of hemoglobin S and C and their association with malaria episodes in two populations of different ethnic origins in eastern Sudan

  • Niven Salih, Institute of Endemic Diseases,University of Khartoum,Sudan, Sudan
  • Rihab Berair, University of Khartoum, Sudan
  • Prof Eltahir Khalil, University of Khartoum, Sudan
  • Ibrahim Elhassan, Institute of Endemic Diseases,University of Khartoum,Sudan, Sudan
  • Hani Gibael, University of Khartoum, Sudan
  • Domminique Kwiatkowski, Wellcome Trust Centre for Human Genetics, United Kingdom
  • Muntasir Ibrahim, Institute of Endemic Diseases,University of Khartoum,Sudan, Sudan

    • Background:There is a scarcity of studies among Sudanese populations on the possible association of abnormal hemoglobins particularly S and C to the spectrum of malaria episodes seen in the country.
    Here we study the frequencies of hemoglobins S and C in two different villages inhabited by two ethnic groups (Hausa and Massalit) in a malaria endemic area in Eastern Sudan. We test for the association of these abnormal hemoglobins with clinical and asymptomatic malaria episodes in these populations.
    Method: A total of 544 individuals from the two villages were genotyped for HbA, HbS and HbC using ARMS PCR. Protein electrophoresis was carried out to confirm the genotypes. Allele frequencies were calculated from 308 unrelated individuals. P. falciparum infection was established by microscopic examination.
    Results: Allele frequencies of HbA, HbS and HbC in Hausa were respectively 0.6813, 0.2473 and 0.0714. The frequencies of the three alleles in Massalit were 0.7330, 0.1877 and 0.0780.
    Genotype frequencies in Hausa were in Hardy-Weinberg equilibrium (p = 0.85). Departure from HWE was seen in Massalit (p=0.004). The calculated Odds Ratio for clinical malaria versus no malaria in Hausa for HbS was (OR: 0.58, P= 0.13), and for HbC (OR: 0.94, P= 0.80). In Massalit it was (OR: 0.46, P= 0.02) for HbS and (OR: 0.25, P= 0.03) for HbC. In asymptomatic versus clinical malaria in Hausa, the odds ratio for HbS was (OR: 2.22, P= 0.01) and for HbC (OR: 1.96, P= 0.19). In Massalit, the odds ratio for HbS was (OR: 2.0, P= 0.07) and for HbC (OR: 1.12, P= 0.55).
    Discussion:The findings confirm that HbS and HbC do not protect against infection but can protect against clinical episodes of malaria in the two populations. The frequencies of HbS and HbC genotypes in the two populations of Hausa and Massalit correlate well with frequencies of asymptomatic malaria in the two villages. Interestingly this is the first report of a high frequency of HbS in an indigenous Sudanese population (Massalit, a Nilo Saharan speaking group). Previous Data have pointed to gene flow and a possible recent introduction of HbS from West Africa into the country (Bayoumi et al,1986, Mohamed et al., 2006). The data also suggests the presence of a strong selective pressure through malaria since the introduction of the S gene, explaining the elevated frequency of HbS.
    *OR: Odd Ratio

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