Malaria and the Sickle Cell Gene

      One of the most fascinating things I have ever learnt about malaria is the relationship between malaria and  the sickle cell gene. First I will give a little background about the sickle cell gene. Normal red blood cells that carry oxygen around the body are shaped like biconcave discs.
        In people with sickle cell anemia, the red blood cells have a sickle or crescent shape, hence they are unable to effectively carry oxygen around the body like they should. Those who are homozygous for this gene have the genotype HbSS and they are said to have sickle cell anemia. Those who are heterozygous for this gene have the genotype HbAS and they are said to have the sickle cell trait. These people do not experience any of the complications of sickle cell anemia.   This change in shape of RBCs is caused by  an abnormal type of hemoglobin called hemoglobin S. People who are heterozygous for the sickle cell gene meaning the have one allele for the normal hemoglobin and one allele of the sickle hemoglobin have been found to have increased immunity against malaria.
       It has been found that there is a high frequency of the sickle cell gene in places where malaria is endemic despite the many deaths from complications of sickle cell anemia among homozygotes in these areas.This is an example of natural selection. The high frequency of this gene has been found to be due to the selective advantage conferrred by HbAS against malaria mortality. In other words, even though people who are homozygous for this gene experience multiple complications and deaths, nature still keeps this gene at a high frequency in those areas to which malaria is endemic because of the protection that the gene offers agianst malaria.

References

1. Khairy, K., Foo, J. J., & Howard, J. (2010). Shapes of red blood cells: Comparison of 3d confocal images with the bilayer-couple model. Cell Mol Bioengineering , 1(2-3), 173-181. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2963995/

2. Thomas, N. W., Mwangi, T. W., & Roberts, D. J.  et al (2005). An immune basis for malaria protection by the sickle cell trait. PLOS Medicine, 2(5), 0041-0045. Retrieved from http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.0020128

Use of Insecticide Treated Mosquito Nets In Combination with Insect Repellents To Prevent Malaria

        Some of the measures used to control malaria infection in tropical places includes the use of insecticides and mosquito nets or a combination of both. Tourists who intend to travel to tropical or subtropical regions where malaria is endemic are often advised to use insecticide treated mosquito nets. According to research, to increase the effectiveness of the use of these nets, they have to be used at the times when mosquitoes feed the most in that area. For example in some areas the vectors feed in the early evening. Research has shown that the effectiveness of this prevention method in these areas can be increased by using the nets between dusk and bedtime.
      A study published in the British Medical Journal was conducted to determine if there was a decrease in the incidence of malaria infection if the mosquito nets were also treated with plant based mosquito repellents. The study was conducted in Bolivia. In this study, all the participants used insecticide treated mosquito nets. One group also used a plant plant based insect repellent and another group used a placebo. The results of the experiments showed a 80% decrease in the the infecion rate of plasmodium vivax, one of the types of parasites that cause malaria in that region in the group that used the net and the plant based repellent.
     The researchers concluded that insect repellents can provide protection against malaria in areas where the vectors bite in the early evening if used appropriately.

References

1.  Hill, N., Lenglet , A., & Arnez , A. M. (2007). Plant based insect repellent and insecticide treated bed nets to protect against malaria in areas of early evening biting vectors: Double blind randomized placebo controlled clinical trial in the bolivian amazon. British Medical Journal, 1023. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC207866

2. Takken W. Do insecticide-treated bednets have an effect on malaria vectors? Trop Med Int Health. 2002 Dec;7(12):1022-30. Review. PubMed PMID: 12460393. Retrieved from www.ncbi.nlm.nih.gov/pubmed/12460393.

What is Malaria?

       According to the NIH website,  malaria is a parasitic disease that can be contacted through mosquito bites. The disease can be contacted when a human is bitten by an infected anopheles mosquito. When the parasite enters the body, it affects the red blood cells which burst open and subsequently affect other red blood cells. The signs and symptoms of malaria infection include fever, shaking, chills, loss of appetite, nausea, vomiting, joint pain and discomfort and anemia but are not limited to these.

     The parasites stay in the red blood cells where they multiply for about 48-72 hours before the red blood cells burst open. The bursting of the red blood cells increases the amount of free hemoglobin in the blood stream. An individual might start to experience the signs and symptoms of malaria as early as eight days or as late as one year after infection. 

     According to the CDC, there are about 300-500 million cases of malaria each year and approximately a million people die from it every year. A large number of the people that die from Malaria are children. The disease is a major public health issue in tropical climates. Some of the measures used to try to prevent malaria infection in tropical climates include use of mosquito nets and spraying of insecticides. However, an increased resistance to insecticides is being seen.

References

1. Dugdale , D. C., & Vyas, J. M. National Institute of Health, (2011). Malaria. Retrieved from website: http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001646/

2. Global Health, Department of Parasitic Diseases. Center For Disease Control, (2010). Where malaria occurs. Retrieved from website: http://www.cdc.gov/malaria/about/distribution.html