CDC - Malaria - About Malaria - Biology - Protective Effect of Sickle Cell
The evolutionary link between sickle-cell trait and malaria resistance showed that humans can and do adapt. But are the “bugs” that make us sick evolving as. The link between sickle cell disease and malaria is a very good example of how genetic variation can provide immunity from diseases. PDF | Sickle cell anaemia is a major chapter within haemolytic In this brief review, in keeping with the theme of this journal, we. focus on the close and complex relationship betweeen this blood disease and this infectious disease. The simplest explanation of this fact is that malaria makes the anaemia.
In subgroup analysis of individuals with SCT, malaria exposure was associated with reduced school enrollment adjusted OR 0.
Conclusions SCT appears to reduce incidence of malaria. Overall, children with SCT do not appear to attend more years of school; however children who get malaria despite SCT appear to have lower levels of enrolment in education than their peers.
A growing literature has documented the importance of human genetic variations in the exposure to, and transmission of, malaria. Genes with protective traits against malaria have been shown to occur with increased frequencies in malaria-endemic regions. Among the genetic variations which offer protection against malaria are those that determine red blood cell RBC haemoglobin disorders in general, and those that cause thalassaemia and sickle cell disease SCD in particular.
SCD is a classic example of a balanced polymorphism: Subjects with one allele HbAS — the sickle cell trait, hereafter referred to as SCT are generally perceived to not suffer immediate negative health consequences, but to benefit from protection from malaria infection and mortality.
There is also suggestive evidence that these protective effects translate into cumulative health benefits such as reduced rates of stunting [ 5 ].
Both SCD and SCT are very common in sub-Saharan Africa, and have been demonstrated to occur with high frequency in areas with high malaria transmission. There is a large literature suggesting that malaria explains an important component of the lagging development performance of sub-Saharan Africa [ 6 ].
However, these studies largely rely on ecological designs; for example several compare educational outcomes for individuals born in more versus less malarial areas prior to national eradication campaigns. As such they may be subject to confounding biases.
Link between Sickle Cell Disease and Malaria | Blood Diseases
Research which examines educational outcomes as a function of individual, rather than geographic, variation in malaria exposure is needed. The genetic variations generated by SCD provide an opportunity to identify the effect of malaria exposure in childhood on educational attainment.
Using the technique of Mendelian randomization, the key assumption is that a specific genotype in this case HbAS is linked to a health-related characteristic protection from malariabut is unrelated to other confounding variables or to the outcome of interest [ 13 ]. Soares, open the way to new therapeutic interventions against malaria, a disease that continues to inflict tremendous medical, social and economic burdens to a large proportion of the human population.
Sickle cell anemia is a blood disease in which red blood cells reveal an abnormal crescent or sickle shape when observed under a conventional microscope.
Link between Sickle Cell Disease and Malaria
It is an inherited disorder - the first ever to be attributed to a specific genetic modification mutationin by Linus Pauling two-times Nobel laureate, for Chemistry inand Peace, in The cause of sickle cell anemia was attributed unequivocally to a single base substitution in the DNA sequence of the gene encoding the beta chain of hemoglobin, the protein that carries oxygen in red blood cells.
Only those individual that inherit two copies of the sickle mutation one from their mother and the other from their father develop sickle cell anemia. If untreated, these individuals have a shorter than normal life expectancy and as such it would be expected that this mutation would be rare in human populations. This is however, far from being the case.Understanding Sickle Cell Trait and Disease
Individuals carrying just one copy of the sickle mutation inherited from either the father or mother were known not to develop sickle cell anemia, leading rather normal lives. The researchers have envisioned the journey from infection to illness to recovery as a loop. The infected mosquito bites the person and transfers the malarial parasite into his bloodstream that keeps multiplying inside the cell, hidden from the immune system.
The parasite ultimately ruptures its own cellular refuge and, in the process, releases toxins which damage the surrounding tissue. These variables, when plotted on a graph, resembled the above recovery loop.
Protective Effect of Sickle Cell Trait Against Malaria-Associated Mortality And Morbidity
The plot of number of red blood cells against the number of immature red blood cells revealed that animals had a loop that took them from health to illness and back to health.
Sickle cell carriers are able to fend off malaria. Immunologists have long observed and shown that mice with a sickle-cell mutation had increased tolerance to malaria.