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Chapter 7

8 Malaria [chapter 7] textbook notes.docx

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University of Toronto Scarborough
Health Studies
Caroline Barakat

Chapter 7: Malaria, Another Fever Plague Malaria is a fever plague -Said to kill half the ppl who ever live on planet and continues to kill till today Every 5 secs, mostly children under 5 in Africa -Number of cases estimated to be 300-500 million, with 10% outside of Africa -Annually 2-3 million deaths A Look Back  Antiquity of malaria: in Ebers papyrus [1570 BC]  Clay tablets in King Ashurbanipal  Chinese medical text ‘Nei Chang’ [2700 BC] oRecords typically describe the typically enlarged spleen, periodic fevers, headaches, chills, and fever oPossibly came to Europe from Africa through Nile valley and people close contact with those of Asia Minor  Greek physician, Hippocrates discussed 2 kinds of malaria:  One with recurrent fevers every third day [benign tertian]  Another with fevers on the fourth day [quartan] o Noted that people living near marshes had enlarged spleens Disease was so prevalent in marshland of Roman campagna, called the ‘roman fever’ believed that fever recurred during sickly summer season die to “vapors” emanating from marshes; called Italian name of “mal’aria”=bad air spread across Europe, in England by 14 and brought to new World by Europeans explorers, colonists and slaves 1800s; worldwide 1880, Charles Louis Laveran, French physician in Algeria, examined drop of blood taken from a soldier with malaria fever under microscope  Found in red blood cells transparent globules containing black- brown malaria pigment  Also mobile filaments emerging from clear spherical bodies; process called ‘exflagellation’  Some patients had b-cells shaped like crescents  He discovered an animal parasite How did bad air cause malaria? Ronald Ross; a surgeon in Indian medical service, published papers on malaria, claiming it was an intestinal infection He visited Dr. Patrick Manson, who took a drop of blood from a sailor ill with malaria and showed Ross the parasite peppered with the black-brown malaria pigment Ross began to think that mosquitoes had the disease and began to dissect o He ignored the brown spotted-winged mosquito anopheles; which was the actual carrier of malaria o Zygotes: spherical cells into which the flagella had penetrated, turning into oocysts o Experiments with sparrows showed that malaria was not conveyed by dust or bad air [July 28 1898]  Giovanni Grassi: anopheles mosquitoes that carry malaria, work showed that the association of the disease with swampy, marshy areas of the world is due to the fact that these are ideal breeding sites for mosquitoes  Ross didn’t complete the proof of mosquito transmission with human malaria, Italians did  Ross flagged the dapple-winged mosquito as the vector  Grassi contributed by recognizing the vector as the ‘Anopheles’  Ross received Nobel prize in 1902 and Laveran in 1907  malaria can be induced in a host by the intro of sporozoites though bite of an infectious female mosquito, but parasite don’t appear immediately in blood clear now that when an infected female anopheline mosquito feeds, it injects sporozoites st that go to liver 1 ; where they live and multiply for several weeks The Disease Malaria over 170 species, but four ‘Plasmodium’ are specific for humans human malarias caused by P. falciparum, P. vivax, P. ovale, & P. malariae  All transmitted through bite of an infected female anopheline mosquito when during blood feeding she injects sporozoites from her salivary glands # Of sporozoites inoculated is usually less than 25 Travel via bloodstream to the liver; they enter liver cells, entire process less than 1 hour Within liver cell; parasite multiplies asexually to produce 10,000 or more infective offspring Don’t return to the liver but instead invade erythrocytes The asexual reproduction of parasites in red blood cells & their ultimate destruction with release of infectious offspring [merozoites]  Responsible for the pathogenesis of the disease  When released from erythrocytes they can invade other red b-cells  w/ 10 fold parasite x and large red b-cell destruction Some cases merozoites enter red cells but don’t divide, instead differentiate into male/female gametocytes [crescents of Laveran] Detailed cycle of growth on page 146 all of pathology of malaria is due to parasite x in erythrocytes primary attack of malaria starts with: headache, fever, anorexia, malaise, myalgia followed by paroxysms of chills, fever, profuse sweating may be nausea, vomiting and diarrhea reason why malaria is frequently called “great imitator” depending on the species the paroxysms assume a characteristic periodicity  P. vivax, ovale and falciparum the period b/w fever burst is 48h  P. malariae it is 72h  Fever corresponds to the rupture of red cell as merozoites are released from infected red cell anemia is the most immediate pathological consequence of parasite x & destruction of erythrocytes there can also be suppression of red cell production in the bone marrow 1 few weeks of infection spleen is palpable b/c swollen from accumulation of parasitized red cells and profilaraion of white cells  At this time soft and easily ruptured, if treated spleen returns to normal size  Chronic infections spleen continues to enlarge becoming hard and blackened in color due to malaria pigment  Long-term consequences of malaria; enlarged spleen and liver and organ dysfunction P. falciparum infections are more severe; can lead to death rate of 25% malaria complications: kidney insufficiency, kidney failure, fluid-filled lungs, neurological disturbances, and severe anemia in pregnancy can result to stillbirth, lower birth weight than normal, abortion nonimmune people/children can develop cerebral malaria [mechanical blockage of microvessels in brain b/c of sequestration of infected red cells]  falciparum malaria; 50% of all clinical malaria cases, responsible for 95% of deaths P. vivax results in severe and debilitating attacks but is rarely fatal, 45% of clinical cases the benign quartan malaria, P. malariae may persist in body for 4 decades without signs of pathology  p. malariae and p. ovale; 5% of clinical cases “Catching” Malaria most important of tropical parasitic diseases [but can exist in temperate areas] present 90 countries in world considered malarious [half in Africa south of Sahara] malaria occurred anywhere that the vector and par
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