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Lecture 8

Lecture 8 Notes

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University of Toronto Scarborough
Health Studies
Caroline Barakat

HLTA01 – Lecture 8 Notes Thursday, November 8 , 2012 Malaria *NOT A ZOONOTIC DISEASE* Overview  Malaria is a fever plague  Malaria killed more than half of the people who have ever lived on this planet, and still does  Today, every 10 seconds a person dies of Malaria, mostly children under the age of 5, living in Africa  Malaria infections are on the rise, and as the fever plague spreads, it will continue to affect us in the places we live, work, travel to and fight in History  Old disease o Dates back to 2700 BC, written in the ‘Nei Chang’ documents th o Dates back to the 4 century (470-380 BC), also written in the ‘Hippocratic corpus’  First document that was written about the splenetic changes due to malaria and about the ingestion of stagnant water  "Those who drink [stagnant water] have always large, stiff spleens and hard, thin, hot stomachs, while their shoulders, collarbones, and faces are emaciated; the fact is that their flesh dissolves to feed the spleen..."  Hippocratus went as far as the define the different types of Malaria rd  Reoccurring fever every 3 day: Benign tertian malaria  Every 4 day: Quatrain malaria o Both known up to present day, due to the different parasites (from the same family) causing the disease  Noted those living near marshes had enlarged spleens  Roman Fever (27 BC)  Due to Malaria o Belief: resulting from poisonous vapours that emanate from ‘Roman Campagna’  Miasma  ‘Bad air’  Mal’aria means ‘bad air’ th  Reached Spain and Russia by 12 century  Reached England by 14 century th  Reached New World by 15 century o Belief that European settlers brought Malaria to New World from Africa  By 1800’s, Malaria was worldwide  By the 19 century: Prevalent in the Mississippi Valley, North Eastern US, American subtropics, and tropics including the Caribbean Malaria in Literature  Written about ‘The Inferno’ by Dante (1265-1321): 1 o "As one who has the shivering of the quartan so near,/ that he has his nails already pale/ and trembles all, still keeping the shade,/ such I became when those words were uttered." o He died of Malaria  William Shakespeare (1564 – 1616) o Mentioned in 8 of his plays  “ague”  English word for ‘malaria’  Demonstrates how much of an epidemic it was back then  Charles Louis Alphonse Laveran (1845-1922) o First person to identify parasite o Observed infected red blood cells of an infected individual under microscope  Observed black-brown malaria pigment and mobile filaments  Process he called exflagellation (1880)  William MacCallum and Eugene Opie o Correctly interpreted their observations: the gametocytes of Haemoproteus in the blood, when ingested by a biting fly, release the gametes in the stomach, where fertilization takes place, producing a wormlike zygote, the ookinete  Robert Koch (1898) o Argued that human malaria was caused by a mosquito bite but was unsuccessful in his efforts  Ronald Ross and Patrick Manson o Credited for discovering the cycles and etiology of malaria o Ronald Ross was an MD interested in Malaria  Knew that it was intestinal infection  Was mentored by Manson; Ross performed a series of experiments in India o Ross examined the stomachs of thousands of mosquitoes  There are different mosquitoes that act as vectors, and firstly observed the wrong types  Finally examined correct type and observed:  Wart-like oocysts that developed 4 -5 days after feeding on infected blood  Stripes or ridges that develop 7 – 8 days later  Made mosquitoes feed on infected individuals, were transferred over, and then infected mosquitoes fed on Ross and his son o Observed in his infected blood that it was in fact malaria o Was then treated and cured on mild malaria  Discovered:  Infectious stages in the mosquito salivary glands in the birds, sparrows  Giovanni Battista Grasi (1898) o Reported that the Anopheles claiger (type of mosquito), was the vector/carrier of human malaria 2 Epidemiology (WHO, 2006)  Estimated that Malaria has killed more than half the people who have ever lived on this planet  Estimated that every 10-30 seconds, a person dies of malaria  Globally, 300-500 million cases of Malaria each year o ~90% of the cases are from Africa  2-3 million deaths annually o Majority is among children aged 5 years or younger  Weak immunity; can’t handle symptoms  death occurs  Currently endemic in over 100 countries o In order for there to be an epidemic, the specific types of mosquitoes that are vectors must be present in that country  Most prevalent in rural tropical areas below elevations of 1000m o Ideal breeding grounds for mosquitoes and malaria  Plasmodium falciparum is found mostly in the tropics o Most dangerous type of malaria  most likely to cause death  P. falciparum and P. vivax account for 95% of infections o P. vivax is distributed more widely than P. falciparum, but it causes less morbidity and mortality  Malaria deaths are poorly reported  very underestimated  Areas of Concern: Figure 1: (Sub-Sahara Africa) o Above: Areas related to sensitivity to different drug treatments Figure 2: 3 o Above: Areas related to where malaria transmission occurs o Also measured by areas related to the spleen rates  larger spleens related to seriousness of malaria  Reoccurring malaria = larger spleens Figure 3: o Above: Number of cases of Malaria, globally 4 Figure 4: o Above: Areas related to the prevention of Malaria  High transmission rates in high dense population areas = increased risk of Malaria Global Malaria  Current project: Known as MAP (Malaria Atlas Project) (2008) o First spatial map of global malaria risk: many of the people exposed to malaria are at a lower risk than previously thought o Found that 2.37 billion people are at risk of contracting malaria from P. falciparum - but about 1 billion of them live under a much lower risk of infection than was assumed by previous historical maps Epidemiology in Canada  Reportable communicable disease in Canada since 1929 o Must be reported o But… estimated that only 30% to 50% of cases are reported to public health agencies  No longer endemic in Canada o It’
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