Malaria Infection Of Protozoa Genus Plasmodium Biology Essay


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Malaria is a life threatening disease ,which is caused by infection with protozoa of the genus Plasmodium. It, is the most important parasitic disease in tropical countries. Malaria remains one of the major killers of humans worldwide, threatening the lives of more than one-third of the world's population. It thrives in the tropical areas of Asia, Africa, and Central and South America, where it strikes millions of people. Each year 350 to 500 million cases of malaria occur worldwide. Sadly, more than 1 million of its victims, mostly young children, die yearly.

There are four species of Plasmodium that infect man and result in four kinds of malarial fever: P. falciparum, P. vivax, P. ovale, and P. malariae . P. falciparum is most common in tropical and subtropical areas. It causes the most dangerous and malignant form of malaria without relapses .Every year 700,000 to 2.7 million people are infected by Plasmodium falciparum and hence contributes to the majority of deaths associated with the disease. Since both vector and parasites have developed resistance to traditional therapeutic tools, strategies for malaria control have been addressed to design new therapeutic alternatives.

Experimental methods such as the inhibition of in-vitro Plasmodium falciparum [3] Trager W, Jensen J. Human malaria parasites in continuous culture. Science 1976;193:673-5 or the test of peters in mice[4] Peters W. Chemotherapy and drug resistance in malaria, vol. 1. Academic Press, Inc.; 1987 are used in the development of new therapeutic alternatives which allows evaluation of the drug activity by the quantification of the parasite growth in blood smears. Methods namely biochemical tests(parasitic lactate hydrogenase LDH), flurometric methods(FluorocromHoecht 33258-AND of plasmodium falciparum), or incorporation of the radio labeled precursors(Hypoxanthine tritiated, actual gold standard in malaria drug research, have been used to estimate the parasitic growth. [5] Bacon DJ, Jambou R, Fandeur T, Bras JL, Wongsrichanalai C, Fukuda MM, et al. World Antimalarial Resistance Network (WARN) II: in vitro antimalarial drug susceptibility. Malar J 2007:6. Because of high cost, specialized infrastructure needs and difficult handling ,the above mentioned tests are rarely used in developing countries. [6] Mitiku K, Mengistu G, Gelaw B. The reliability of blood film examination for malaria at the peripheral health unit. Trop Med Int Health 2000;5:3-8. Malaria quantification in the thin blood smears by means of light microscopy remains the most widely and commonly used method because it provides an efficient and reliable alternative compared to other methods. The staining process highlights the Plasmodium falciparum parasite and allows to distinguish erythrocytes and parasites.

Evaluation of stained slide is a routine and time-consuming task, difficult to reproduce, especially in situations where large numbers of samples require reliable analysis, and subjective which results in large inter and intra-observer variance. Different cells in microscope images can be differentiated by human visual analysis by using only the spatial and intensity information. After the blood cell slides have been analyzed, they are kept away. There is no quick and easy way of retrieving analyzing lot of images for future reference as with a computerized system. Some decision makers in emergency situations may not have accessed to test results before having to decide on treatment and they may have no experience of a particular rare condition and therefore not recognize it or not know how to deal with it. Emotional problems and fatigue degrade the expert's performance. Besides a recent study on the field shows the agreement rates among the clinical experts for the diagnosis are surprisingly low. Hence, it is very important to produce a common standard tool, which is able to perform diagnosis with same ground criteria uniformly everywhere. Many doctors and many pathologists identify this problem. Hence, it is important to develop a automatic parasitemia quantification from the thin blood films stained with Giemsa for the research of new therapeutic alternatives.

Quantification problems

Automatic quantification of thin blood smears infected with Plasmodium falciparum is a 2 fold problem.[10] Fidock DA, Rosenthal PJ, Croft SL, Brun R, Nwaka S. Antimalarial drug discovery: efficacy models for compound screening. Nat Rev Drug Discov2004;3:509-20. Besides precise counting of the number of infected erythrocytes, an estimation of which parasite life stage an erythrocyte is infected with is also needed which poses multiple challenges from image processing point of view. Firstly, inevitable variations either at the sample preparation, dye fabrication or parameterization of image parameters introduces large luminance differences even though they are captured from the same slide. Another fact is that most laboratories need to adapt the stain technique to the particular environment conditions because modifications of the staining procedure can mistake the entire detection technique.

Estimation of the life cycle stage per infected erythrocyte in highly important in terms of the evaluation of anti-malarial therapies. FIGURE showing the life cycle stages of falciparum.(figure three stages of plasmodium falciparum. The different infection stages are determined by their morphological characteristics and a correct classification is highly dependent on the observer experience because a slight difference among life stages may present feature overlapping features. Explain the figure containing the life cycle stages,talk about the various distinguishing features of each stage.

In addition it should be noted that any automatic quantification approach demands very low error values since parasitemia in case of Plasmodium falciparum is under a 6 % so that detection of any parasitemia variation should be under a 1%.

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