Malaria

11 Key excerpts on "Malaria"

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  Emerging Infections

  • John I. Gallin, Anthony S. Fauci(Authors)
  • 1998(Publication Date)
  • Academic Press

    (Publisher)

  This chapter reviews Malaria as an emerging infection in the context of up- to-date considerations of the biology and epidemiology of Malaria. Five key fac- tors have been identified which have or are currently influencing the increased global threat of Malaria. These are discussed in Section 4 after a general discus- sion of relevant biology and epidemiology in Sections 2 and 3. In Section 5, I briefly address the threat of global warming and how this may worsen the 468 KAREN P. DAY Malaria situation. I conclude with a discussion of the prospects for the future (Section 6). II. THE BIOLOGY OF PLA$MODIUM SPP. Malaria in humans is caused by infection with protozoan parasites of the genus Plasmodium. Four species of Plasmodium infect humans, namely, Plasmodium falciparum, P. vivax, P. Malariae and P. ovale. The former species is considered to be the most virulent as it causes the condition known as cerebral Malaria, which is often fatal. All four species are transmitted by anopheline mosquitos. A. Life Cycle Key features of the life cycle are the requirement of transmission between the anopheline and human host with expansion of the parasite population in both hosts by asexual replication in a range of tissues such as liver and bloodstream in the human host and the mosquito midgut. The basic Malaria life cycle is shown in Fig. 3. One P. falciparum sporozoite transmitted by a mosquito bite can invade a liver cell, which after 8 to 10 days can release 10,000 merozoites capable of invading erythrocytes. Replication of parasites in erythrocytes and their subsequent release from these cells results in induction of fever and im- mune responses which cause the characteristic pathology of Malaria. The pro- duction of transmission stages, known as gametocytes, results after commit- ment of infected cells to sexual development. Patterns of gametocyte production differ among the Plasmodium spp.

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  Parasitic Protozoa

  Babesia and Plasmodia

  • Julius P. Kreier(Author)
  • 2012(Publication Date)
  • Academic Press

    (Publisher)

  C H A P T E R 4 Plasmodi a off Human s Francisc o J. Lopez-Antunan o an d Gabrie l A. Schmuni s I Introductio n Malaria in humans is an infection caused by parasites of the genus Plasmodium, class Sporozoa, that are transmitted in nature by the bite of an infected female mosquito of the genus Anopheles. The disease caused by this parasite usually is characterized by intermittent febrile paroxysms, anemia, and spleen enlargement (Russell, 1968; Bruce-Chwatt, 1985). When parasites multiply in the bloodstream and invade more than 1% of the red blood cells, a cascade of effects may produce a severe and complicated disease that can terminate in coma and death of the victim if adequate diagnosis and proper treatment are not provided in time (Hall, 1976). The most common synonyms for Malaria in the English language are Roman, marsh, jungle, intermittent, paroxysmal, and periodic fever; ague (Bruce-Chwatt, 1976); and chills and fever. In other languages and in cultures in which Malaria is endemic, the variety of terms for Malaria is enriched by the people's interpretation of the disease or by the imagination of writers and poets. When, how, and why plasmodia invaded humans is a rather philosophical question that will not be addressed in this chapter. However, we will share the perspective of the Greek physicians of the fifth century B .C. , who were very familiar with Malarial fevers and the association of those diseases with marshes. In his book Airs, Waters, and Places, Hippocrates (English translation by Jones, 1923) states his belief in the balance between humans and their environment; this statement constitutes the first known systematic endeavor to present a causal relationship between environmental risk factors and disease.

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  Tropical Medicine

  A Clinical Text, 8th Edition, Revised and Expanded

  • Kevin M. Cahill(Author)
  • 2013(Publication Date)
  • Fordham University Press

    (Publisher)

  Even advances in technology—such as the availability of blood banks and transfusions—and changes in societal practices—such as the explo- sion in intravenous drug abuse—have contributed to the spread of Malaria, especially in the more affluent parts of the world. In Europe, the United States, Australia, and most of the former Soviet Union, where endemic Malaria had been eradicated, the growth of rapid and relatively cheap air travel has been accompanied by a sharp increase in imported Malaria, and airport outbreaks have become a new phenome- non in the Western world. Physicians everywhere must be familiar with the clinical and therapeutic aspects of Malaria because there is no other disease that can pass so rapidly from a mild illness, the treatment of which is relatively simple, to a catastrophic state in which the outlook is virtually hopeless. Failure to consider Malaria in differential diagno- sis, or the inability to recognize parasites in a blood smear, can be a fatal error. The Parasite Four species of the genus Plasmodium commonly cause disease in human beings. These are P. vivax (benign tertian), P. ovale (ovale ter- tian), P. Malariae (quartan), and P. falciparum (malignant tertian). The 6 Malaria life cycles of these four Malarial parasites are broadly similar, with sex- ual development (sporogony) occurring in appropriate Anopheline mos- quito hosts, and asexual maturation (schizogony) occurring in man. FIGURE 1: (A) P. vivax ameboid trophozoites and a presegmenting schizont. Note prominent Schuffner’s dots. FIGURE 1: (B) Mixed infection with P. vivax and P. falciparum. During the act of biting an infected person, Anopheles mosquitoes may ingest male and female gametocytes. The male exflagellates in the insect gut and fertilizes a female parasite. The resulting oocyst then enlarges in the stomach wall of the mosquito for 7 to 20 days before rupturing into the body cavity, releasing thousands of sporozoites.

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  Imported Infectious Diseases

  The Impact in Developed Countries

  • Fernando Cobo(Author)
  • 2014(Publication Date)
  • Woodhead Publishing

    (Publisher)

  An eight-fold increase in the number of imported Malaria cases between 1972 and 1988 was reported for the Malaria programme in the WHO European Region, followed by a more gradual rise in 2000. More than 70% of cases reported were from France, the UK, Germany and Italy.

  The proportion of imported Malaria cases in immigrants in Europe has increased during recent years from 14% to 83%. VFRs travelling to sub-Saharan Africa have more than eight times the risk of acquiring Malaria compared to tourists, and more than twice the odds ratio after travelling to Asia (especially child VFRs).

  Malaria infection among immigrants can increase the risk of transmission in some areas that have vectors and certain climatic conditions (for example, in Greece in 2011); furthermore, imported Malaria in immigrants could also have an important role in transmission through organ transplantation, blood transfusion or occupational exposure.

  There are also a few cases of transmission of Malaria at airports where Anopheles mosquitoes carrying Malaria parasites are transported by aircraft to non-endemic areas.

  6.3 Biology and ecology of Malaria

  The natural biology of Malaria involves three components – Malaria parasites infect both human hosts and female Anopheles hosts. Fig. 6.2 shows the complete life cycle.

  Figure 6.2 Life cycle of the Malaria parasite

  In human beings, Plasmodium spp. grows and multiplies first in the hepatocytes of the liver and then in the erythrocytes of the blood. In the blood (asexual erythrocytic cycle), parasites grow inside the erythrocytes, leading to their destruction, and releasing daughter parasites (called merozoites) that continue the cycle by invading other red cells. This blood stage causes the main symptoms of Malaria. Several forms of blood-stage parasites (gametocytes) can be picked up by a female Anopheles mosquito during a blood meal, thus beginning another different cycle of growth and multiplication in the mosquito. After 10–15 days, the parasites are found as sporozoites in the mosquito’s salivary glands.

  When an infected mosquito bites a person, the sporozoites are injected with the mosquito’s saliva under the skin. They travel through the bloodstream to the liver and mature within hepatocytes to become tissue schizonts. Up to 30 000 parasites are released into the bloodstream as merozoites and produce symptomatic infection as they invade and destroy red blood cells. However, some parasites remain in a dormant stage in the hepatic tissue as hypnozoites, which may mature between two and 11 months or more after the initial infection. These are the parasites that cause relapsing Malaria in P. vivax and P. ovale infection. Once within the bloodstream, merozoites invade erythrocytes via receptors such as Duffy factor in P. vivax

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  The Political Ecology of Malaria

  Emerging Dynamics of Wetland Agriculture at the Urban Fringe in Central Uganda

  • Matian van Soest(Author)
  • 2020(Publication Date)
  • transcript Verlag

    (Publisher)

  It is rather the constraints that Malaria has posed to colonial powers and their administrations and armies that have made it the number-one topic of tropical medicine, in itself a discipline that developed out of the colonial encounter and late 19th-century imperialism (Chakrabarti 2014: 141-163; Neill 2012: 205; Packard 1997: 281). Mark Nichter reminds us that “[…] the very representation of “tropical diseases” is problematic. It is a carryover from colonial medicine, when diseases common to the tropics were responded to by military-style campaigns enabling economic and military expansion” (2008: 153). During the colonial conquest of Africa by European forces, Malaria has repeatedly posed a major challenge to the invading troops, who at times were swept away in their hundreds by the tertian fevers (cp. Chakrabarti 2014: 126-140). In other cases, like the construction of the Panama Canal, it was the workers, brought in from Ja-maica, Martinique, and Barbados, who fell victim to Malaria in thousands (Harri-son 1978: 157-160). No wonder then, that colonial powers were desperately looking for a solution to the problem. Towards the end of the 19th century epidemiologists, physicians, and biologists were eagerly looking to decipher the transmission route of the disease. Malaria is ranked among the vector-borne diseases, as the infection occurs with the bite of a mosquito. What can almost be considered common knowledge today was suspected for a long time and finally proven in 1897 by Ronald Ross, when he succeeded in isolating the Malaria pathogens discovered earlier, in 1880, by the French military doctor Alphonse Laveran, from the guts of an Anopheles mosquito. It took another ten years until the complex life-cycle of the Plasmodium parasite had finally been unraveled, revealing the fatal relation between humans, parasites, and mosquitoes (Müller 2011: 24-27). 7 The Plasmodium parasite needs both – humans as well as mosquitoes – as hosts in order to procreate.

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  Protozoa and Human Disease

  • Mark F Wiser(Author)
  • 2010(Publication Date)
  • Garland Science

    (Publisher)

  Disease(s) Malaria Etiological agent(s) Plasmodium falciparum, P. vivax, P. ovale, P. Malariae Major organ(s) affected Blood Transmission mode or vector Anopheline mosquitoes Geographical distribution Tropical and subtropical regions throughout the world Morbidity and mortality Causes an acute febrile disease that in the case of P. falciparum can develop into a complicated disease involving several organs and lead to death if not treated Diagnosis Detection of parasites in blood Treatment Chloroquine, mefloquine, quinine, Fansidar®, artemisinin derivatives combined with other drugs, plus others Control and prevention Mosquito avoidance such as use of bed nets, repellents, protective clothing; chemical or biological control of mosquitoes and destruction of breeding areas; case detection and treatment Malaria 15 Table 15.1 Some historical highlights in the description of Malaria and the parasite Year Person Feature described 500 BC Hippocrates Clinical symptoms 1880 Laveran Blood-stage parasite 1898 Ross Mosquito transmission 1948 Garnham Liver stage of life cycle 168 CHAPTER 15: Malaria Malaria is caused by apicomplexan parasites (Chapter 11) of the genus Plasmodium . The parasite exhibits a heteroxenous life cycle involving a vertebrate host and an arthropod vector. Vertebrate hosts include: reptiles, birds, rodents, monkeys, and humans and the most common arthropod vector is a mosquito. Plasmodium species are generally host and vector specific in that each species only infects a limited range of hosts and vec-tors. Four distinct species infect humans: P. falciparum , P. vivax , P. ovale , and P. Malariae . These four species differ in regard to their morphology, details of their life cycles, and their clinical manifestations. P. falciparum and P. vivax are the most prevalent and each species accounts for about 40% of the total Malaria cases. In addition, there have been some reports of humans naturally infected with the simian parasites on rare occasions.

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  Advances in Malaria Research

  • Deepak Gaur, Chetan E. Chitnis, Virander S. Chauhan, Deepak Gaur, Chetan E. Chitnis, Virander S. Chauhan(Authors)
  • 2016(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  CHAPTER 4 The biology of Malaria transmission Robert E. Sinden

  The Malaria Centre, Department of Life Sciences, Imperial College London, London, UK

  The Jenner Institute, University of Oxford, Oxford, UK

  Purpose

  For the purposes of this text, transmission is defined as the progression of Plasmodium from a vertebrate host through the mosquito vector until inoculation into the next vertebrate host. Thus this chapter examines the biology of the infectious gametocyte in the vertebrate host, of the sexual and sporogonic development in the mosquito vectors, and of the delivery of infectious sporozoites into the proboscis of the mosquito.

  History

  Since the 1970s, the focus of Malaria research has been on the cyclic development of the pathogenic asexual blood stages of Plasmodium falciparum; it is therefore perhaps necessary to recall that Plasmodium was first identified when Laveran saw the explosive emergence of the male gametes in a sample of blood taken from a soldier in Tunis (Laveran 1881). The appreciation of the role of these lashing cells was memorably summarized by Manson in his advice to Ross: “Follow the flagellum!” In so doing, Ross discovered that it was mosquitoes that are the most common vectors of Plasmodium (Ross 1897), and Grassi and colleagues recognized that Anopheles transmitted the Malaria parasites to humans (Grassi 1900). McCallum soon recognized that the flagellum was indeed the male gamete and that fertilization took place in the mosquito, resulting in the formation of a motile “vermicule” (MacCallum 1897), thus making the vectors the definitive hosts of Plasmodium.

  Recognition of the key role of the mosquito in transmission led to the early and very effective implementation of environmental, housing, and personal schemes to reduce human–vector contact and the early introduction of both residual and targeted household insecticide spraying campaigns, notably in the protection of colonial forces. The success of the introduction of DDT into such campaigns is difficult to overestimate.

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  Infectious Diseases

  • (Author)
  • 2014(Publication Date)
  • Research World

    (Publisher)

  Over the longer term, developmental impairments have been documented in children who have suffered episodes of severe Malaria. ________________________ WORLD TECHNOLOGIES ________________________ Causes A Plasmodium sporozoite traverses the cytoplasm of a mosquito midgut epithelial cell in this false-color electron micrograph. Malaria parasites Malaria parasites are members of the genus Plasmodium (phylum Apicomplexa). In humans Malaria is caused by P. falciparum , P. Malariae , P. ovale , P. vivax and P. knowlesi . P. falciparum is the most common cause of infection and is responsible for about 80% of all Malaria cases, and is also responsible for about 90% of the deaths from Malaria. Parasitic Plasmodium species also infect birds, reptiles, monkeys, chimpanzees and rodents. There have been documented human infections with several simian species of Malaria, namely P. knowlesi , P. inui , P. cynomolgi , P. simiovale , P. brazilianum , P. schwetzi and P. simium ; however, with the exception of P. knowlesi , these are mostly of limited public health importance. Malaria parasites contain apicoplasts, an organelle usually found in plants, complete with their own functioning genomes. These apicoplast are thought to have originated through the endosymbiosis of algae and play a crucial role in various aspects of parasite metabolism e.g. fatty acid bio-synthesis. To date, 466 proteins have been found to be produced by apicoplasts and these are now being looked at as possible targets for novel anti-Malarial drugs. ________________________ WORLD TECHNOLOGIES ________________________ Life cycle The parasite's secondary (intermediate) hosts are humans and other vertebrates. Female mosquitoes of the Anopheles genus are primary hosts and transmission vectors. Young mosquitoes first ingest the Malaria parasite by feeding on an infected human carrier and the infected Anopheles mosquitoes carry Plasmodium sporozoites in their salivary glands.

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  Malaria Immunology

  • P. Perlmann, M. Troye-Blomberg, T. A. E. Platts-Mills(Authors)
  • 2002(Publication Date)
  • S. Karger

    (Publisher)

  Mol Biochem Parasitol 1999;104:195–204. 124 Yoshida S, Ioka D, Matsuoka H, Endo H, Ishii A: Bacteria expressing single-chain immunotoxin inhibit Malaria parasite development in mosquitoes. Mol Biochem Parasitol 2001;113:89–96. 125 Crampton JM, Stowell SL, Karras M, Sinden RE: Model systems to evaluate the use of transgenic haemoatophagous insects to deliver protective vaccines. Parasitologia 1999;41:473–477. 126 Ribeiro J, Kidwell MG: Transposable elements as population drive mechanisms: Specification of critical parameter values. J Med Entomol 1994;1:10–16. Prof. R.E. Sinden, Department of Biology, Imperial College of Science, Technology and Medicine, London SW7 2AZ (UK) Tel. 44 207 594 5425, Fax 44 207 594 5424, E-Mail [email protected] Malaria in the Mosquito 49 Perlmann P, Troye-Blomberg M (eds): Malaria Immunology. Chem Immunol. Basel, Karger, 2002, vol 80, pp 50–69 Malaria: Pathogenicity and Disease Mike English, Charles R.J.C. Newton Kenya Medical Research Institute and Wellcome Trust Research Laboratories, Kilifi, Kenya Introduction Falciparum Malaria is the most important cause of morbidity and mortality resulting from the four human plasmodium species. This chapter deals almost exclusively with this pathogen, although work on other species has contributed to our understanding of the pathogenicity of Malaria. Currently approximately 400 million people world-wide are infected with Malaria and there are thought to be 130 million new cases of Malaria each year. Estimates of attributable mor-tality suggest that over 1 million people die each year from Malaria [http://www. nature.com/nm/specialfocus/Malaria, Wahlgren M, 2000]. The great burden of disease is in sub-Saharan Africa where 90% of all deaths occur, the majority of these in children. For this reason the principal focus of this chapter will be on our understanding of the pathogenicity resulting in disease in African children.

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  Gregarines, Haemogregarines, Coccidia, Plasmodia, and Haemoproteids

  • Julius Kreir(Author)
  • 1977(Publication Date)
  • Academic Press

    (Publisher)

  falciparum (Rieckmann et al., 1974b) and cured volunteers in-fected with such a strain (Trenholme et al., 1975b). Although prelimi-nary findings are most encouraging, the value of this 4-quinoline-methanol compound in the widespread prophylaxis and treatment of drug-resistant Malaria remains to be determined. X. Epidemiology A. Measurement of Transmission Since the beginning of this century, much consideration has been given to understanding the factors which affect the transmission of Malaria and to measuring the prevalence of the disease in the community (Russell et al., 1963; Black, 1968). The interrelationship between human, mosquito, and climatic elements is complex and it may vary considerably from time to time and from place to place. Increase in the prevalence of Malaria has been associated with migrations, wars, poverty, and poor agricultural practices. The activities of the community and its domestic animals, the location of housing in relation to mosquito breeding sites, and various environmental factors may profoundly influence the course of the disease. In many instances man-made Malaria results from in-adequate drainage of surface water after engineering projects, land rec-lamation or agricultural development. The effectiveness of an anopheline species as a vector of human Malaria depends on its biting habits (pref-erence for or availability of animals surrounding man, outside or inside dwellings, time of night, etc.), its preferred breeding site, its suscepti-bility to infection, and its longevity. Important climatic factors include temperature, humidity, rainfall, and wind. Mosquitoes feed once every 2 days under lowland tropical conditions, but only once every 3 days at cooler highland temperatures. The extrinsic sporogonic cycle in the mosquito cannot usually be completed if the environmental temperature is below 16°C or above 33°C, but between these limits, the develop-mental cycle is shorter at the higher environmental temperatures.

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  Landscapes of Disease

  Malaria in Modern Greece

  • Katerina Gardikas(Author)
  • 2018(Publication Date)
  • Central European University Press

    (Publisher)

  C H A P T E R I Malaria: AN ANCIENT AND GLOBAL DISEASE 16 CHAPTER I tion. 2 This is also true with regard to the arrival of the disease on the shores of the Mediterranean, where, in fact, the narrative begins to tread on firmer ground only by the time of late antiquity. The evolutionary history of the disease predates the encounter of ma-laria with humankind. The genus Plasmodium dates as far back as the Cam-brian period, about 500 to 600 million years ago. 3 How did the four species of human Plasmodia 4 evolve among human groups? By virtue of their an-cient history and their concomitant polymorphisms, the Plasmodium spe-cies have a privileged position in their adaptive arms race with humans, over whom Plasmodia possess a considerable evolutionary advantage. P. fal-ciparum , for instance, contains one of the most polymorphic genes in ex-istence, the gene encoding for the antigen termed merozoite surface pro-tein 1 (MSP1), which is critical for the ability of the parasite to invade human red blood cells. 5 The extremely high degree of diversity of molecule MSP1 would have required some forty-eight million years of random mu-tation, but this diversity was actually achieved, not by chance, but by nat-ural selection within the parasite’s recent history of a few thousand years, thanks to the antigen’s interaction with the human immune system in the process, on the part of the Plasmodium , to try to evade recognition and break into the human red blood cells. 6 Thus, much of the research into the history of P. falciparum , a history of mutual adaptation between invader and defender, has been based on the degree of polymorphism of certain an-tigens. As a result of research along these lines, S. M. Rich and F. J. Ayala place the origin of present-day P. falciparum to a cenancestor, or common ancestor, as recently as 5,000 to 50,000 years ago.

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