Malaria Year 4 Internal Medicine Notes OmpathStudy

Malaria Year 4 · Internal Medicine Collection: 4TH YEAR ALL NOTES / IMED / IMED 4.3 / MOGERE -- Slide 1 Malaria Dr Alex Mogere Consultant physician Slide 2 Introduction Malaria is a protozoan disease transmitted by the bite of infected Anopheles mosquitoes. \nMalaria has been eliminated from the US, Canada, Europe, and Russia; its prevalence rose in many parts of the tropics Increases in the drug resistance of the parasite, the insecticide resistance of its vectors, and human travel and migration have contributed to this resurgence. Slide 3 Epidemiology Kenya has four malaria epidemiological zones, with diversity in risk determined largely by altitude, rainfall patterns and temperature. The zones are: Endemic Seasonal transmission Epidemic prone areas of western highlands of Kenya Low risk malaria areas Slide 5 Aetiology 5 species of the genus Plasmodium cause nearly all malarial infections in humans: P. falciparum,\nP. vivax,\nP. ovale\nP. malariae,\nP.knowlesi—in Southeast Asia—the monkey malaria parasite Slide 7 Pathogenesis: malaria transmission cycle Slide 9 Ct pathogenesis In P. vivax and P. ovale infections, a proportion of the intrahepatic forms do not divide immediately but remain inert for a period ranging from 3 weeks to ≥1 year before reproduction begins.\nThese dormant forms, or hypnozoites, are the cause of the relapses that characterize infection with these two species After entry into the bloodstream, merozoites rapidly invade erythrocytes and become trophozoites For P.falciparum PfRh5 is indispensable for erythrocyte invasion Most West Africans and people with origins in that region carry the Duffy-negative FyFy phenotype and are therefore resistant to P. vivax malaria Slide 10 Ct pathogenesis By the end of the intraerythrocytic life cycle, the parasite has consumed two-thirds of the RBC’s Hb and has grown to occupy most of the cell(schizont)\nThe disease in human beings is caused by the direct effects of the asexual parasite—RBC invasion and destruction—and by the host’s reaction After release from the liver,some of the blood-stage parasites develop into morphologically distinct longer-lived sexual forms (gametocytes) that can transmit malaria Slide 11 Epidemiology P. falciparum predominates in Africa, New Guinea, and Hispaniola (i.e., the Dominican Republic and Haiti);\nP. vivax is more common in Central America. \nP. malariae is found in most endemic areas, especially throughout sub-Saharan Africa, but is much less common.\nP. ovale is relatively unusual outside of Africa and, where it is found, comprises <1% of isolate Slide 12 CT epidemiology: endemicity Endemicity traditionally has been defined in terms of parasitemia rates or palpable-spleen rates in children 2–9 years of age and classified as: hypoendemic (<10%),\nmesoendemic (11–50%),\nhyperendemic (51–75%), and\nholoendemic ( 75%). Slide 13 Ct. epidemiology Constant, frequent, year round infection is termed stable transmission\nIn areas where transmission is low, erratic, or focal, full protective immunity is not acquired, and symptomatic disease may occur at all ages(unstable transmission).\nThe principal determinants of the epidemiology of malaria are the number (density), the human-biting habits, and the longevity of the anopheline mosquito vectors.\nThe entomologic inoculation rate (the no. of sporozoite- positive mosquito bites per person per year) is the most common measure of malaria transmission and varies from <1 in some parts of Latin America and Southeast Asia to 300 in parts of tropical Africa Slide 14 Ct. epidemiology The geographic distributions of SCD, Hbs C and E, hereditary ovalocytosis, the thalassemias, and dehydrogenase G6PD deficiency closely resemble that of f. malaria before the introduction of control measures.\nThis similarity suggests that these genetic disorders confer protection against death from f. malaria Slide 15 Clinical presentation Slide 16 Ct.Clinical presentation The fever is usually irregular at first (that of falciparum malaria may never become regular);\nIn nonimmune individuals with acute malaria, the spleen takes several days to become palpable,\nsplenic enlargement is found in a high proportion of otherwise healthy individuals in malaria-endemic areas and reflects repeated infections Slide 17 Ct. clinical presentation: severe malaria uncomplicated falciparum malaria (i.e., the pt can swallow medicines and food) carries a mortality rate of <0.1%. once vital-organ dysfunction occurs or the total proportion of erythrocytes infected increases to 2% (a level corresponding to 10^12 parasites in an adult), mortality risk rises steeply. Slide 18 Severe F. malaria Slide 19 Ct severe malaria Slide 20 Features indicating a poor prognosis in severe malaria Slide 21 Ct.Features indicating a poor prognosis in severe malaria Slide 22 Cerebral malaria Coma is a characteristic and ominous feature of falciparum malaria Coma is associated with death rates of ~20% among adults and 15% among children Cerebral