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Malaria in the Asia-Pacific Region

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Malaria in the Asia-Pacific Region Volume 13 | Issue 45 | Number 1 | Article ID 4395 | Nov 09, 2015 The Asia-Pacific Journal | Japan Focus Malaria in the Asia-Pacific Region J. Kevin Baird Summary borne of a well-to-do urban worldview. In truth, the Asia-Pacific region is rife with endemic Despite its relative invisibility to most people malaria and it faces challenges in mitigating living in the urban Asia-Pacific, endemic and eliminating this serious problem. malaria occurs across the region. The unique character of Asian-Pacific malaria includes a The challenges are steep. There is no vaccine serious problem of drug resistance, dominance against malaria. Emerging strains of drug- of a particularly difficult species to control and resistant malaria threaten incurable infections. treat, and another that normally dwells in Some infections cannot be treated safely and monkeys but often infects humans. Most patients suffer repeated clinical attacks over nations in the region with endemic malaria many months. Other infections derive from have called for its elimination by the year 2030. forest-dwelling monkeys. About two billion Meeting that ambitious goal will require throughout the Asia Pacific live at risk of the mobilizing technical and financial resources, infection and tens of millions contract it each and social and political will. Malaria is a year.1 Unknown numbers, perhaps as many as formidable foe fully capable of defeating half- two hundred thousand each year, do not hearted efforts to eliminate it. survive the malaria attack.2 This article explores the Asia-Pacific malaria problem and Key Words: Malaria, public health, control, the misplaced broad public complacency treatment, elimination regarding it. Introduction The highest risk in urban centers is not malaria itself, but ignorance of or indifference to the Many well-educated people think of malaria as malaria occurring in rural areas. The educated, a single disease that is largely, if not entirely, empowered and endowed sectors of Asia- isolated to the African continent. This includes Pacific metropolises can act against malaria in many living in the enormous urban centers of the region if they see and understand the the Asia-Pacific. They go about their daily lives formidable problem and the challenges faced in in gleaming modern cities with convenient eliminating it from the region. This article aims access to professional clinical care. Some may at such awareness. worry about dengue fever, and an unlucky few will actually contract it. Others will be more What is Malaria? anxious about threats like MERS-CoV or particular strains of influenza that are much Malaria is a term that encompasses a wide less common than dengue, but with much variety of diseases caused by single-celled higher fatality rates. There are no vaccines or parasites in the genus Plasmodium. There are cures for these viral infections. Malaria, by over 170 species in this genus that infect comparison, is not only thought of as a distant particular species of mammals, birds and threat, but is also widely believed to be reptiles. Only 5 species are known to routinely completely preventable and curable with infect humans:Plasmodium falciparum, inexpensive simple therapies. This is an illusion Plasmodium vivax, Plasmodium malariae, 1 13 | 45 | 1 APJ | JF Plasmodium ovale, and Plasmodium knowlesi. the cyclical nature of the intense fever and Among these, P. falciparum and P. vivax cause chills of a malaria attack. If the infection is not the vast majority of infections. All of these properly diagnosed, or the patient waits too parasites follow a complicated life cycle that long before seeking treatment, the infection depends upon particular species of mosquitoes can progress to death in people who lack a in the genus Anopheles. The ability to transmit partial immunity by prior chronic exposure to malaria by these species varies among them malaria. This is true of all of the species of like the ability to play chess among humans – malaria, but especiallyP. falciparum, P. from those who don’t know how to grand knowlesi, and P. vivax. Even with prompt masters. While it is true that mosquitoes carry diagnosis and appropriate treatment, these malaria from one person to another, in a infections (excepting P. malariae) lead to strictly biological sense the parasites use intense illness with complete debilitation for at humans to carry malaria from one mosquito to least several days. It is a devastating illness another – the plasmodia have sex in the and fatal if not properly managed. The causes mosquito, which makes it, and not us, the of death by malaria are many, including coma, definitive host for these parasites. Figure 1 severe anemia, respiratory distress, liver or illustrates the life cycle of P. vivax, which is kidney failure, and shock. only slightly different from the other species, but in an important way to be explained later in One of the primary reasons malaria tends to be this article. almost invisible is its affinity for impoverished and isolated rural areas, and its aversion to urban environments. Access to quality healthcare in cities bodes poorly for parasite survival. Further, the anopheline mosquito vectors do not survive in urban environments and are not found there. The single known exception to this rule is a particular species, Anopheles stephensi, which thrives in the massive cities of India and causes a great deal of malaria in them. That species adapted to breeding in sunlit pools of clean rooftop water created by air conditioning units. Most mosquito vector species, however, have no tolerance of urban grime. Malaria victimizes the poorest of the poor in rural settings, those Figure 1. The extraordinary complexity in the life having limited access to rudimentary health cycle of malaria parasites, with the human liver at care that governments struggle to deliver to lower left, the human blood stream at lower center, the many remote peripheries of modern and the gut and salivary glands of anopheline mosquitoes at upper right. From the WHO as adapted civilization. These people are among the most from Mueller et al.3 invisible to us, and they suffer tremendously in vast numbers from malaria and other diseases endemic to the Asia-Pacific. About a week or so after being bitten and infected, people begin to show symptoms as Malarious Asia-Pacific parasites emerge from the liver and begin infecting red blood cells. The invasion, rupture A glance at a world map of the levels of malaria and reinvasion of red blood cells account for prevalence reveals what most residents of the 2 13 | 45 | 1 APJ | JF Asia-Pacific do not realize – that malaria is not Notice that the distribution of P. vivax reaches solely an African problem, it is all around us much farther north than P. falciparum. There right here in the region, and quite a lot of it. are a couple of important reasons for this. The two maps of Figure 2 show the distribution First, this species develops quicker at lower of the two dominant species of parasites that ambient temperatures in its cold-blooded cause malaria, P. falciparum and P. vivax. mosquito host, allowing it to thrive in Wherever there is color, even if blue, indicates temperatures P. falciparum cannot tolerate. stable transmission of malaria, meaning it is Secondly, P. vivax is able to place dormant almost always present. The dark grey areas forms in the human liver (called hypnozoites, indicate unstable transmission, where malaria see Fig.1), providing it a safe haven during the is only sometimes present. Figure 3 zooms in harsh winters on the Korean Peninsula, for on the Asia-Pacific and reveals theexample, when there can be no mosquitoes to extraordinary patchwork of transmission, both transmit them. broad swaths of persistent stable transmission along with a scattering of both very high risk and risk-free pockets. Figure 3. Maps showing the distribution of malaria risk in the Asia Pacific forPlasmodium Figure 2. Maps showing the distribution of malaria falciparum (top) and Plasmodium vivax(bottom). risk globally forPlasmodium falciparum (top) “PR” indicates prevalence rate, or the percentage of and Plasmodium vivax (bottom). See color keys in residents found infected by malaria parasites in Figure 3. Courtesy of theMalaria Atlas Project, population surveys of blood by microscopic University of Oxford, United Kingdom. examination. The scales between P. falciparum and P. 3 13 | 45 | 1 APJ | JF vivax differ for biological and epidemiological experimental formulation of the drug in 1943.6 reasons. Courtesy of theMalaria Atlas Project, Licensed in the USA in 1946, its useful life University of Oxford, United Kingdom. began to unravel at the border between The World Health Organization monitors Thailand and Cambodia in the 1960s. The malaria reporting globally, and in 2013 it parasite P. falciparum evolved a means of estimated a total of 11.2 million cases ofP. surviving chloroquine, and with continued use vivax in the Asia-Pacific, along with 25 million the resistant strains overwhelmed and cases of P. falciparum.4 That’s 36.1 million dominated the sensitive strains. Over the attacks of malaria in the region. Someensuing 20 years, those resistant strains spread scientists believe these WHO estimates are around the globe. Millions are thought to have 5 lost their lives to infections by resistant strains underestimated by a large degree. 7 Remarkably, in the instance of P. vivax, over treated with what had become a useless drug. 80% of all attacks globally occur in the Asia- Eventually, after a great deal of research and Pacific, making this principally a regional advocacy for change, chloroquine was replaced problem. with a new class of drugs called the artemisinins – discovered by a medical science Malaria Problems of the Asia Pacific unit of the Chinese Army working in support of the North Vietnamese during the war with the Malaria as a public health problem varies Americans (by the 2015 Nobel laureate Dr.
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