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MALARIA causative agent = Plasmodium species

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Presentation on theme: "MALARIA causative agent = Plasmodium species"— Presentation transcript:

1 MALARIA causative agent = Plasmodium species
40% of world’s population lives in endemic areas 3-500 million clinical cases per year million deaths (90% Africa) known since antiquity early medical writings from India and China Hippocrates usually credited (500 BC) Laveran identified parasite (1880) Ross demonstrated mosquito transmission (1898) Garnham described liver stage (1940’s)

2 Clinical Features characterized by acute febrile attacks (malaria paroxysms) periodic episodes of fever alternating with symptom-free periods manifestations and severity depend on species and host status immunity, general health, nutritional state, genetics recrudescences or relapses can occur over months or years can develop severe complications (especially P. falciparum)

3 Malaria Transmission natural (sporozoites/Anopheles)
blood transfusions shorter incubation period fatality risk (P. falciparum) no relapses possible (vivax/ovale) syringe sharing congenital relatively rare although placenta is heavily infected

4 Febrile Attack (Malaria Paroxysm)
Prodromal Symptoms end of incubation period 2-3 days before 1st paroxysm includes: malaise, fatigue, lassitude, headache, muscle pain, nausea, anorexia (i.e., flu-like symptoms) can range from none to mild to severe Febrile Attack (Malaria Paroxysm) periodic febrile episodes alternating with symptom-free periods initially fever may be irregular before developing periodicity may be accompanied by splenomegaly, hepatomegaly (slight jaundice), anemia

5 cold stage feeling of intense cold vigorous shivering, rigor
lasts min

6 hot stage intense heat dry burning skin throbbing headache
lasts 2-6 hours

7 sweating stage profuse sweating declining temperature
exhausted, weak  sleep lasts 2-4 hours


9 Malaria Paroxysm paroxysms associated with synchrony of merozoite release temperature is normal and patient feels well between paroxysms falciparum may not exhi-bit classic paroxysms continuous fever 24 hr periodicity tertian malaria quartan malaria

10 Karunaweera et al (1992) PNAS 89:3200
sweating rigor TNF = tumor necrosis factor-a () proinflammatory cytokine (produced in response to malarial antigens?)

11 Other Features of the Paroxysms
may be accompanied by spleno-megaly, hepatomegaly (slight jaundice), hemolytic anemia P. falciparum can be lethal in non-immune (eg., children, expatriates) paroxysms become less severe and irregular as infection progresses semi-immune may exhibit little (1-2 days fever) or no symptoms

12 Immunity Anti-Parasite Immunity
slow to develop short lived ‘premunition’ non-sterilizing lower parasitemia less symptoms Anti-Parasite Immunity immune response prevents merozoite invasion, eliminates infected erythrocytes, etc. Anti-Disease Immunity eg., neutralization of exo-antigens or toxic effects

13 Current Distribution of Malaria
tropical and subtropical climates formerly widespread in temperate zones (ague) 40% of worlds population live in endemic regions

14 Distribution of Malarial Parasites
P. vivax most widespread, found in most endemic areas including some temperate zones P. falciparum primarily tropics and subtropics P. malariae similar range as P. falciparum, but less common and patchy distribution P. ovale occurs primarily in tropical west Africa

15 Malaria Epidemiology Stable or Endemic Malaria
~constant incidence over several years includes seasonal transmission immunity and disease tolerance correlates with level of endemicity (especially adults) Unstable or Epidemic Malaria periodic sharp increase in malaria little immunity high morbidity and mortality Endemicity Levels: holo- hyper- meso- hypo-

16 Roper et al (1996) AJTMH 54:325 eastern Sudan (mesoendemic, seasonal)
rainy season June-Sept. peak symptomatic malaria Oct.-Nov. followed cohort of 79 individuals using thick films and PCR (P. falciparum)

17 Mosquito Transmission
susceptibility of anopheline species feeding habits density longevity climatic factors temperature, humidity, rainfall, wind, etc "Everything about malaria is so moulded by local conditions that it becomes a thousand epidemiological puzzles." Hackett (1937) Anopheles

18 Malaria Control Reduce Human-Mosquito Contact Reduce Vector
impregnated bed nets repellants, protective clothing screens, house spraying Reduce Vector environmental modificaton larvacides/insecticides biological control Reduce Parasite Reservoir diagnosis and treatment chemoprophylaxis

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