Malaria continues to select for sickle cell trait in Central Africa (original) (raw)
Related papers
Sickle Cell Trait and the Risk of Plasmodium falciparum Malaria and Other Childhood Diseases
The Journal of Infectious Diseases, 2005
Background. The gene for sickle hemoglobin (HbS) is a prime example of natural selection. It is generally believed that its current prevalence in many tropical populations reflects selection for the carrier form (sickle cell trait [HbAS]) through a survival advantage against death from malaria. Nevertheless, 150 years after this hypothesis was first proposed, the epidemiological description of the relationships between HbAS, malaria, and other common causes of child mortality remains incomplete. Methods. We studied the incidence of falciparum malaria and other childhood diseases in 2 cohorts of children living on the coast of Kenya. Results. The protective effect of HbAS was remarkably specific for falciparum malaria, having no significant impact on any other disease. HbAS had no effect on the prevalence of symptomless parasitemia but was 50% protective against mild clinical malaria, 75% protective against admission to the hospital for malaria, and almost 90% protective against severe or complicated malaria. The effect of HbAS on episodes of clinical malaria was mirrored in its effect on parasite densities during such episodes. Conclusions. The present data are useful in that they confirm the mechanisms by which HbAS confers protection against malaria and shed light on the relationships between HbAS, malaria, and other childhood diseases. Malaria causes 1200 million episodes of febrile illness and 11 million deaths every year in young children living in sub-Saharan Africa [1, 2]. The factors determining which children die and which survive are complex, but they are likely related to both the host and the parasite. Of the host-specific factors, the sickle cell trait (HbAS) remains the best described [3], having been shown to confer strong protection against Plasmodium falciparum malaria in numerous studies conducted in various countries over the course of 150 years [4-10]; nevertheless, the protective mechanisms at work remain incompletely understood. A number
Malaria and Early African Development: Evidence from the Sickle Cell Trait
2013
We examine the effect of malaria on economic development in Africa over the very long run. Using data on the prevalence of the mutation that causes sickle cell disease we measure the impact of malaria on mortality in Africa prior to the period in which formal data were collected. Our estimate is that in the more afflicted regions, malaria lowered the probability of surviving to adulthood by about ten percentage points, which is roughly twice the current burden of the disease. The reduction in malaria mortality has been roughly equal to the reduction in other causes of mortality. We then ask whether the estimated burden of malaria had an effect on economic development in the period before European contact. Examining both mortality and morbidity, we do not find evidence that the impact of malaria would have been very significant. These model-based findings are corroborated by a more statistically-based approach, which shows little evidence of a negative relationship between malaria ecology and population density or other measures of development, using data measured at the level ethnic groups.
Experimental Parasitology, 1997
Sickle-cell trait is associated with higher prevalence of multiple infections in Gabonese children with asymptomatic infections. Experimental Parasitology 87, 39-46. Through PCR amplifications of the gene encoding the merozoite surface antigen 2, utilizing allele-specific 3D7 and FC27 probes, we have examined the prevalence of Plasmodium falciparum in children aged from 7 to 14 years living in a village located in the equatorial forest region of Central Africa (Gabon). Using this technique, 61% (100/163) of the blood samples were shown to be infected with P. falciparum with 24 alleles distinguished by size polymorphism and sequence type. The two main families (3D7 and FC27) and hybrid alleles were detected regardless of sex and hemoglobin phenotype. No age-related changes in prevalence of P. falciparum strains were observed; however, the prevalence of infection (42%) was significantly lower in individuals with the sickle-cell trait compared with their normal-hemoglobin counterparts (68%). Mixtures of genetically distinct parasite clones were present in 82% of children carrying the sickle-cell trait but in only 58% of normal-hemoglobin carriers. The significance of these observations regarding the design and interpretation of epidemiological investigations is discussed in the context of malaria transmission in the region studied.
The protective effect of sickle cell haemoglobin against severe malaria depends on parasite genotype
bioRxiv (Cold Spring Harbor Laboratory), 2021
Host genetic factors can confer resistance against malaria, raising the question of whether this has led to evolutionary adaptation of parasite populations. In this study we investigated the correlation between host and parasite genetic variation in 4,171 Gambian and Kenya children ascertained with severe malaria due to Plasmodium falciparum. We identified a strong association between sickle haemoglobin (HbS) in the host and variation in three regions of the parasite genome, including nonsynonymous variants in the acyl-CoA synthetase family member PfACS8 on chromosome 2, in a second region of chromosome 2, and in a region containing structural variation on chromosome 11. The HbS-associated parasite alleles are in strong linkage disequilibrium and have frequencies which covary with the frequency of HbS across populations, in particular being much more common in Africa than other parts of the world. The estimated protective effect of HbS against severe malaria, as determined by comparison of cases with population controls, varies greatly according to the parasite genotype at these three loci. These findings open up a new avenue of enquiry into the biological and epidemiological significance of the HbS-associated polymorphisms in the parasite genome, and the evolutionary forces that have led to their high frequency and strong linkage disequilibrium in African P. falciparum populations. .
Journal of Integrated Health Sciences, 2017
Sickle cell disease (SCD) though initially restricted to certain geographical places, now has become a global problem due to migration. 1, 2 Epidemiology of SCD is same as malaria, which is considered to be a disease of tropics. World distribution of sickle gene has remained same like that of past and present malaria. 3 Sickle gene is thought to be result of mutation to protect local community from death due to plasmodial disease. 3 Thus, relationship between malaria and genetic disorders like thalassemia, Sickle cell disorder and glucose-6-phosphate dehydrogenase deficiency (G6PD) is an example of interaction of gene with environment. 3,4,5 Mediterranean region, Africa and Asia which has archives of high malaria prevalence is also native for hemoglobinopathies. Migration and resettlement of communities has made SCD, a global problem which is common in America, Australia and Europe, as well. 1 Continent of Africa has high prevalence of malaria as well as SCD. As per WHO, in 2015, 214 million new cases of malaria were reported of which 88% were in Africa. 6 SCD is also very common in Africa, where 3% of newborn are affected and high mortality (50%-90%) is reported among African children with SCD. 7 ,8 In retrospective hospital based study from The Democratic Republic of Congo, Africa, 90 children of malaria with SCD (homozygous) were admitted. This 10 years study concluded that children below 5 years were at higher risk for acute crises due to malaria. They may need blood transfusion and anti-malarial prophylaxis. 9 Evidence are also available to suggest that sickle cell trait (SCT) is giving protection against malaria mortality and morbidity. It also prevents from heavy parasitaemia and severe anemia due to malaria. 10 However, protection offered is not complete. 9 Malaria-endemic countries who have also high prevalence of SCD, should adopt malaria prophylaxis policy especially for children. 3 In Africa, for comprehensive care, screening, prophylaxis, and treatment of SCD is recommended, however large population based study may tell us about estimate of preventable child deaths by interventions policy and its cost benefit advantage. 7 Again guidelines regarding malarial antiprophylaxis need more precision in varied groups like children, pregnant females, diabetics and immune compromised population.
Background: Sickle cell anaemia is an important genetic and public health problem in Manipur, which is a small hilly state, situated at the north eastern extreme corner of India sharing an international boundary with Myanmar. Our present study provides a comprehensive database on the occurrence of sickle cell trait in the Manipuri population especially with regard to Manipuri Muslims, as till date no work has been done on Manipuri Muslims with different castes.