Association between Sickle Cell Trait and Low Density Parasitaemia in a P. falciparum Malaria Holoendemic Region of Western Kenya

Abstract

Aims:The frequency of the mutant gene for sickle cell is widely distributed in the sub-Saharan Africa, the Middle East, and the Indian subcontinent. There is epidemiologic evidence that sickle cell trait confers a survival advantage against malaria and that the selection pressure due to malaria has resulted in high frequencies of the mutant gene in areas of high malaria transmission. We carried out a study to look at the relationship between sickle cell trait, age, haemoglobin level, and malaria parasite density. Methods: We carried out a cross-sectional study between the months of October and December, 2004 in Kombewa Division of Kisumu West District, a P. falciparum malaria

Association Between Haematological Parameters and Sickle Cell Genotypes in Children With Plasmodium Falciparum Malaria Residents in Kisumu County in Western Kenya

“…In our study, the prevalence of malaria was lower in HbAS (31.1%), in comparison to HbAA (39.2%). Likewise, numerous studies have demonstrated a lower prevalence of malaria among children with HbAS relative to those with HbAA (14,40,41). Our nding is consistent with that of Makani et al among other studies in Africa where sickle cell disease is prevalent and malaria is holoendemic (41).…”

“…Numerous studies have demonstrated protective effect of HbSS from P. falciparum infection compared to HbAS but results in higher morbidity and mortality once the infection occur (14,58,63,65). However, we did not nd any signi cant association between both HbAS and HbSS with P. falciparum infection.…”

“…Our study provides a unique approach by not only looking at the comparisons of the haematological parameters in sickle cell genotypes in P. falciparum infection but also determines the association of these parameters to sickle cell gene in the infection. A few studies have been carried out in African countries where malaria is holoendemic with varied demonstrations on the protective effect of sickle cell gene (HbAS and HbSS) of asymptomatic and symptomatic P. falciparum infection of variable severity (14,20,22,23). None of the above studies have speci cally described haematological differences on the basis of sickle cell genotypes in children presenting with steady state of P. falciparum malaria apart from Prohit et al (24) and…”

“…Plasmodium falciparum is the most deadly and most prevalent species in areas of malaria holo-endemicity including Kisumu in Western Kenya (11,12). Due to this protection associated with SCT, these disorders have reached a balanced polymorphism in malaria holo-endemic regions such as in Kisumu County in western Kenya (13,14). It is thought that SCD make the cell susceptible to haemolysis at reduced thresholds of oxygen and any interior or exterior stressors on the RBC can simply make them haemolyse (14).…”

“…Whenever a gene that has a potential for reducing tness achieves high frequencies in the population, it is assumed that the gene confers a survival advantage (19). Su cient studies including the ones conducted in the same locality in Western Kenya and elsewhere, have demonstrated that individuals who are heterozygous for the HbS are protected from the severe form of malaria infection (9,14,20,21). Malaria confers a selective heterozygous survival advantage to carriers of the HbS gene and this is referred to as balanced polymorphism (18).…”