An Observational Study of the Effect of Hemoglobinopathy, Alpha Thalassemia and Hemoglobin E on P. Vivax Parasitemia

Background The protective effect of α-thalassemia, a common hematological disorder in Southeast Asia, against Plasmodium falciparum malaria has been well established. However, there is much less understanding of the effect of α-thalassemia against P. vivax. Here, we aimed to investigate the proportion of α-thalassemia including the impact of α-thalassemia and HbE on the parasitemia of P. vivax in Southeast Asian malaria patients in Thailand. Methods A total of 210 malaria patients, admitted to the Hospital for Tropical Diseases, Thailand during 2011-2012, consisting of 159 Myanmeses, 13 Karens, 26 Thais, 3 Mons, 3 Laotians, and 6 Cambodians were recruited. Plasmodium spp. and parasite densities were determined. Group of deletion mutation (--SEA, -α3.7, -α4.2deletion) and substitution mutation (HbCS and HbE) were genotyped using multiplex gap-PCR and PCR-RFLP, respectively. Results In our malaria patients, 17/210 homozygous and 74/210 heterozygous -α3.7 deletion were found. Only 3/210 heterozygous -α4.2 and 2/210 heterozygous--SEA deletion were detected. HbE is frequently found with 6/210 homozygotes and 35/210 heterozygotes. The most common thalassemia allele frequencies in Myanmar population were -α3.7 deletion (0.282), followed by HbE (0.101), HbCS (0.013), -α4.2 deletion (0.009), and --SEA deletion (0.003). Only density of P. vivax in α-thalassemia trait patients (-α3.7/-α3.7, --SEA/αα, -α3.7/-α4.2) but not in silent α-thalassemia (-α3.7/αα, -α4.2/αα, ααCS/αα) were significantly higher compared with non-α-thalassemia patients (p=0.027). HbE did not affect P. vivax parasitemia. The density of P. falciparum significantly increased in heterozygous HbE patients (p=0.046). Conclusions Alpha-thalassemia trait is associated with high levels of P. vivax parasitemia in malaria patients in Southeast Asia.