Plasmodium vivax is a human pathogen from the group of microorganisms called the protozoa. It is the causative agent for the recurring malaria. The Plasmodium vivax survives in the body of mosquitoes and it is a unicellular parasite. The parasite causes malaria after the mosquito bites an individual thereby infecting the red blood cells with the parasite. The P. vivax is a common parasite in America. It is found mainly in the United States. It is also found in large numbers across the Latin America. In addition, the parasite is common in parts of Africa. There is evidence that P. vivax is common in Asia and South American region causing an estimated 65 per cent cases of malaria in these regions. Malaria is a tropical disease and is found in both tropical and non-tropical areas. The main reason that makes the parasite prevalent in Asia is the dense population of the region. In fact, the oldest history of P. vivax is for Asia. The parasite is said to have first been found in Asia.
About 80% of the global incidences of P. vivax is concentrated in the Asian region. Globally, approximately 2.85 billion individuals are infected by P. vivax. The regional incidence of the parasite is said to be increasing globally as that of P. falciparum is decreasing (Arnott, Barry, and Reeder, 2012, p 1). As a result, the disease has become an important disease among the human race and raised a lot of concern. There are certain factors that favor the transmission of P. vivax parasite. Some of these factors include globalization, which has enhanced international travels. This has caused widespread of the Anopheles mosquito. In addition, the population is growing at a high rate especially in the Asian parts of the world. Towns become congested and the environmental conditions deteriorate. The conditions favor the breeding of mosquito and subsequently the malaria transmission. Malaria transmission has been increasing even in the previously non-endemic areas (Monga, 2011, p 230). The image of the parasite can be observed as shown below under a microscope.
Mechanism of pathogenesis
The P. vivax is one of the four microorganisms that cause malaria. It causes malaria known as benign tertian. The disease is not highly fatal. However, it is the most difficult malaria to cure. The symptoms of this malaria are not different from the common malaria symptoms. They include fever, headache, and diarrhea. Vomiting is also common. The patient feels weak, and chills can also be experienced. However, the disease has one significant complication, which is the enlargement of the spleen. The parasites become dominant in the liver. As a result, the disease keeps on recurring after months or some years (WHO, 2012 para 5).
The dominant parasites can be killed, but only under specific medication. The microorganism is introduced in the body by the Anopheles mosquito. Plasmodium sporozites pass through the salivary glands of the mosquito and into the blood stream of the human being. Once it gets into the body, it invades the liver cells. In the liver, the plasmodium sporozites invade the hepatocytes. Most of them divide and form schizonts. This might take about 1 to 2 weeks after which they rapture to form large numbers of merozoites. The merozoites then move out of the liver and invade the red blood cells. This stage is referred to as the erythrocytic stage. The merozoites are produced at a very high rate. They are usually in ring forms. They mature to form tropozytes and then the red cell schizonts that cause malaria symptoms (WHO, 2012 para 5).
In fact, after 48 hours, enough of them are already produced to cause symptoms on the patient. It is necessary to note that the sporozoites that are found in the liver stage do not cause malaria. The merozoites formed in the erythrocytic stage are the ones that cause malaria. The parasites digest the red cells proteins found in the hemoglobin. The parasites release toxic substances into the body. These toxics substances are referred to as hemozoin. It is these toxins that cause high fever in the individual. Heme is a non-protein form of hemoglobin that is formed after the blood has been digested by the malaria parasites or any other blood feeding parasites. Free heme spread toxins to the cells. The parasite converts the free heme into hemozoin. The hemozoin can also be referred to as the malaria pigment. It is vital to note that this toxin is the one that enhances survival of the malaria parasite. Therefore, it is essential when developing drugs for malaria cure. The other toxin that the parasite P. vivax can cause is the glycosylphosphatidylinositol (GPI). This toxin makes the macrophages and the endothelial cells active to produce cytokines. There is limited knowledge regarding to virulence mechanisms of the malaria causing organisms. The virulence knowledge that can be identified on the P. vivax is that it infects young red blood cells (RBCs), as opposed to P. falciparum that affects RBCs at all stages (The Rockefeller University Press, 2012, p 567).
Mechanisms of growth in the Lab
Study of P. vivax microorganism in the laboratory is usually very difficult. In fact, the microorganism cannot be grown in a defined medium. The main reason as to why it is not easy to study it in the lab is because the microorganism grows in immature red blood cells. The immature red blood cells can only be derived from the haemopoetic stem cells. The concentration of these cells is usually very low such that it cannot be sufficient for researchers to grow cells infected by P. vivax in the laboratory. It becomes difficult for researchers to perform in vitro experiments, which are crucial for further discovery on drug development. However, there have been recent advances in the study. In these studies, researchers will be seeking to produce a constant supply of immature red blood cells from the stem cells. The cells will then be infected by P. vivax, which will be obtained directly from the patients. A continuous supply of the infected cells will be ensured. This is an alternative to help in studying the microorganism in the laboratory (Tres Cantos Open Lab Foundation, 2011 para 1). The parasites grow in the blood cells outside the human body only in the presence of Locke’s solution and should be free of calcium chloride. Ascetic fluid can also be present (The Rockefeller University Press, 2012, p 567).
The microorganism can be detected in a patient through lab tests. This is the best way to confirm the diagnosis of the disease, in addition to the symptoms manifested. The diagnosis of malaria in the laboratory involves blood tests. It involves identifying the parasite in the blood of the patient. Identification of its antigens in the blood can also be a confirmatory test for malaria. Microscopy is regarded as the best for laboratory confirmatory test for malaria. The technique is simple, and most lab technicians can apply it with minimal problems. A drop of blood from the patient is collected to carry out the test. Blood collection can be through a finger prick. It can also be collected from a large vein such as at the arm (Monga, 2011, p 232).
After the blood has been collected, a blood smear is made on a glass slide. It is then placed in a reagent to stain the parasite. The reagent commonly used is the Giemsa stain. Once this has been done, the smear under a microscope is examined. A magnification of ×1000 can be used to observe the parasites clearly. On observation under the microscope, the parasites are identified by their physical appearance. Alternatively, presence of the parasite can be noted as a result of the appearance of the red blood cells that they have infected. For perfect diagnosis of malaria, it is necessary to understand various morphological features presented by various blood stages of the parasites. One should not rely on a single image to confirm the test. Before drawing conclusions various morphological characteristics should be identified (Antimicrobial Resistance Network, 2009 para 2). The morphological features at different stages are described differently. During the trophozoites stage, the parasite is polymorphus in shape. The shapes are of the form of large rings and amoeboid mass. In a thin smear, they appear as shown in the following diagram:
At the schizonts stage, large bodies containing merozoites are observed. Golden brown pigmentation is also observed. This stage is present in the peripheral blood. They appear as shown in the following diagram.
The gametocytes have large bodies with large nucleus. In addition, the gametocytes have a red or purple nucleus in females. Males have pink nucleus. They appear as shown in the diagram below:
At the parasitic stage the parasites can be easily observed in large numbers (Antimicrobial Resistance Network, 2009 para 3). Other laboratory tests that can be used to detect the disease include antigenic detection, serological tests, and indirect fluorescent antibody test.
Disease Treatment/ Prevention
The best recommended treatment for P. vivax is the use of chloroquine and primaquine. The latter is effective at the liver stage. It helps in decreasing the risk of relapse. However, resistance of the parasite to these drugs is increasing over the recent years (Filho, et al. 2007 para 3). Scientists have been given a wakeup call to do more research so as to discover new drugs, which are not resistance. One of the drugs that have been developed to overcome the resistance is the artesunate. The drug is not used in the United States. The drug is used in combination with primaquine for effective cure to be achieved. Another drug that can be used to treat P. vivax is mefloquine. The drug is readily available in many countries. Atovaquone- proguanil is also effective especially for patients who have developed a resistance to chloroquine. Despite the fact that quinine is not so effective, it can also be used to treat P. vivax malaria. If radical treatment is not offered to the patients, there are high chances that the disease is going to relapse after some time. In fact, the relapse can be as high as 100 per cent of the cases. Therefore, the best way to avoid the occurrence of a relapse is to give radical treatment. Eradication of the disease at the liver stage by use of primaquine is usually effective in avoiding a relapse (Monga, 2011, p 232).
All forms of malaria can be prevented. The spread of malaria is mostly associated with travelers. Therefore, one the efforts that can be used to prevent malaria are to seek advice from a mobile clinician when travelling so as to get advice on the best malaria protection mechanism to adapt. The main reason as to why it is advisable to seek medical advice before travelling is because the effectiveness of the various drugs is not the same in all regions and may also vary with time. In taking the prevention measures, one should evaluate the risk of infection. Then prevention of mosquito bites is also effective which can be achieved by controlling the mosquitoes. Chemoprophylaxis can also be taken as a preventive medication (WHO, 2012 para 7).
Malaria can be attributed to various species of mosquito parasites among which is the P. vivax. The form of malaria caused by this microorganism is not fatal, but is recurring. The recurrence can be avoided through radical treatment. The P. vivax parasite is most common in the Asian countries. As a result of its increasing epidemiology, it has raised so much concern worldwide. Research is still being done to find a solution on its control and how it can be reduced. With the observation of the correct measures, the disease can be controlled.
Antimicrobial Resistance Network (2009), Laboratory Diagnosis of Malaria; Pakistan Antimicrobial Resistance Network. Web.
Arnott, A., Barry, A. E. and Reeder, J. C. (2012). Understanding the population genetics of Plasmodium vivax is essential for malaria control and elimination. Malaria Journal, 11(1): 14-23. Web.
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Monga, S. P. S. (2011). Molecular pathology of liver diseases. New York: Springer. Web.
The Rockefeller University Press, (2012). The Cultivation of Malarial Plasmodia (Plasmodium Vivax and Plasmodium Falciparum) In Vitro. JEM; 16(4): 567. Web.
Tres Cantos Open Lab Foundation (2011). A two-year project to create a continuous lab-based supply of the P. vivax malaria parasite in the blood stage. If successful this project will offer a technology breakthrough that could allow further advances in research on P. Vivax. CRESIB, Spain. Web.
WHO, (2012). International travel and health; World Health Organization. Web.