Evolutionary selection of Malaria in Human Genome
Malaria is a vector-borne disease that affects a huge number of population around the world. The disease is caused by the malaria parasite Plasmodium falciparum, which is transmitted by the mosquito. The wild type disease was found in sub-Saharan Africa almost 42000 years ago (Price, 2018). Till then, the disease causes various changes in human genome and as well as affect the evolution of human. In addition to this, several cultural factors like environmental changes, inheritance of various beliefs and practices, and as well as social systems have contributed to then adaptation of malaria in human. In this essay, the biological and as well as the cultural factors of malaria adaptation is discussed briefly.
Malaria is assumed to be a one of the strongest factor for the evolutionary selection in the history of human evolution. Malarial adaptation has caused in the change in the human genomic level. It is seen that the HbS allele has increased in numbers in the population who have already exposed to the disease. Although there was cases of mortality. Along with this different population around the world has developed various evolutionary changes in response to the exposure of malaria. For example, the HBB gene has 3 coding SNPs to prevent malaria. They are Glu6Val ( HbS), Glu6Lys ( HbC), Glu26Lys (HbE). The HbS is mainly popular in the African region, but it is not found in the Southeast Asia. In addition to global differentiation, local gene pool also showed significant difference in Africa. Presence of different malaria-resistance gene in different places suggested that evolutionary changes has occurred by the effect of malaria(Taylor, Cerami & Fairhurst, 2013). The haplotype analysis and the statistical modelling of G6PD locus indicates that the origin was 10000 years old. Analysis of 100 mtDNA showed that the parasite of the malaria have already existed 100,000 years ago. Although the malaria parasite of Africa had increased almost 10,000 years ago and slowly expanded in various area around the world. This result along with the analysis of polytene chromosome have proved the fact that the malaria parasite acted as the reservoir during the evolutionary procedure of human (Mangano & Modiano, 2014). The variation in the genetic component also suggested towards the matter genetic component of the individual showed various immunological responses against the disease. In relation to this, it can be seen that different ethnic population has evolved different resistance against malaria during the evolutionary process. Although, it is also documented that the ethnic groups who lived in the same region also had different resistance to the malaria. For example, Fulani population are mainly found in the West Africa and lived with other ethnic population. It had observed that, the Fulani population had low rate of malaria prevalence in comparison to other ethnic population lived in that region. Detailed epidemiological studies showed that the resistance against the malaria in Fulani population had come due to genetical evolution that is genetical changes in response to malaria. The Fulani population had more number of antimalarial antibodies and along with this increased amount of IL-4 is also responsible for the protection of malaria (Cherif et al., 2016). In that study, it was revealed that , the IL4-524 T allele was responsible for the high level of antibody against malaria antigen (Calixto Fernandes,2013). In a malaria endemic region, one of the most common genetical alteration was onset of sickle cell anemia. The mutation of sickle cell anemia is a recessive disease that is the disease is found only in the people who two copies of altered gene. The carriers, that is the person who have only one copy of altered gene, showed resistance to malaria. This phenomenon is known as heterozygote advantage. The alteration is closely associated with the human evolutionary process (Gong et al., 2016).
Global Differentiation of Malaria-resistant Gene
Environmental changes mainly the climatic changes cause alteration in the vector borne diseases like malaria. With global climatic change, the concern of disease dynamics has changed globally. The vector of malaria and the parasite responsible for the disease are very much sensitive to the climatic change. In a study, it is seen that the parasite of malaria transmitted well in the temperature range of 30-32 degree centigrade. The required rain- fall level for best transmission of malaria parasite was about 15-17 mm per day (Ngarakana-Gwasira et al., 2016). From this finding, it can be said that the climatic change made the malaria a serious threat throughout the world. In another study it is seen tat between the time of 2000 -2010, the incident of malaria had reduced globally by 17% (Caminade et al., 2014). Environmental pollution is another important factor that contribute to the adaptation of malaria. With growing population, urbanization is also increased. As a result, of urbanization, pollution has also come in to the scenario of malarial development. The larvae of the malaria vector breeds in a clean water. However in a recent study it seen that with growing pollution, the vectors of the malaria also adapt themselves to a polluted water bodies. The study showed that larvae can survive in the polluted condition as well due to the exposure in polluted environment (Bichet et al., 2013). The social and cultural factors are another crucial factors of human evolution in adaptation to malaria. The social and cultural phenomena that are associated with the human evolution are mainly social beliefs, social status, social structures, social roles, and also economic condition. Along with this the health resources is also associated with the economic condition of the human society that is the population who have more power can earn more money and can have more health resources in comparison to the economically backward people in the society. There is a close relationship between the malaria and the literacy rate in the population. The economically backward peopke generally have lower rate of literacy. As a result, they do not have proper knowledge about the disease. As a result, they became more malaria prone. Lack of awareness also promotes outcome of the disease more in the poor people. The social environment promotes malaria by driving them towards the disease during various social activities. One of the major cause of this drive towards the disease is poor economic condition of the people. They have to do various risky economic activity due to their poverty. They are forced to do risky works like deforestation for land and as a result, they are directly exposed to the vector of the malaria. The lack of proper shelter is also another social aspect of malaria. The poor people generally lives in a very congested environment and due to lack of proper knowledge they don’t even know about the fact that malarial mosquito completes their breeding only in the fresh water and as a result they do not maintain proper cleanliness around them. Moreover, they are more exposed to the disease (Rapoport, 2016). The use of bed net was a preventive measure for the malaria, although, the economic condition of the poor people did not allow them to buy the bed net. Another social factor in adaptation to malaria is ignorance local medical cultures of malaria prevention. In relation to the previous fact, people who lives near the forest region, had their own of mosquito prevention and they were not ready to accept the modern culture as this practice had inherited from their previous generations. From very ancient time, malaria was a serious problem. The local population have evolved various measures to combat against malaria by various trial and error method. The local population has learned about the malaria traditionally and as well as locally. For example there is a local belief that malaria is caused by the “ mal-air” that is the bad condition of air is responsible for the disease. This belief was established by the experience and observation of the local people and they established relation among the malaria and humidity of the air. People have understood that they can protect themselves by avoiding the air during the rainy season of the year. Another belief was that, malaria was a related to forests, water bodies and teak flowers and they believed that the disease was nothing but a forest fever. From this believe, they learned to protect themselves from the disease by avoiding the forests near water bodies, and also they avoided forest during the blooming season of teak flower. However there was no documented prove of effectiveness of this beliefs, the people participated in those practice. Those beliefs have inherited over the time from one generation to another. The introduction of modern medical technology introduced contradiction in between the ancient local beliefs and the modern concepts. This resulted in community problem and people gradually became adapted to the modern concepts (O’Neill et al., 2015).
In conclusion, it can be said that the most common vector borne disease around the world, has serious impact on the human genetic evolution and the evolution is also region specific. The entire region in this world has not similar genomic adaptation. Not only the biological factors,but the socio- cultural and environmental factors are also associated with the adaptation process of the malaria. The socio-economic factor and inheritance of ancient beliefs from generation to generation has also left prints of contribution in the adaptation of malaria
References
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Calixto Fernandes, M. H. (2013). IL-3-Polymorphismen und Infektionsdynamik von Plasmodieninfektionen bei Kindern aus der Ashanti-Region, Ghana.
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Price, M. (2018). Dramatic evolution within human genome may have been caused by malaria parasite. [online] Science | AAAS. Available at: https://www.sciencemag.org/news/2017/03/dramatic-evolution-within-human-genome-may-have-been-caused-malaria-parasite [Accessed 29 Sep. 2018].
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