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all erythrocytes invaded Pv/Po = reticulocytes Pm = senescent RBC up to 36 merozoites sequestration of infected erythrocytes trophozoite and schizont.

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Presentation on theme: "all erythrocytes invaded Pv/Po = reticulocytes Pm = senescent RBC up to 36 merozoites sequestration of infected erythrocytes trophozoite and schizont."— Presentation transcript:

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2 all erythrocytes invaded Pv/Po = reticulocytes Pm = senescent RBC up to 36 merozoites sequestration of infected erythrocytes trophozoite and schizont stages primarily in brain, heart, lungs, and gut complications immune evasion (spleen avoidance) Higher Parasitemia in Falciparum Malaria

3 avoidance of spleen low oxygen tensions better invasion

4 Severe Falciparum Malaria Complications Features Indicating Poor Prognosis cerebral malaria anemia hyperpyrexia hypoglycemia acidosis GI and liver syndromes pulmonary edema blackwater fever algid malaria (shock) impaired consciousness repeated convulsions respiratory distress shock acidosis/hyperlactemia hypoglycemia jaundice or other liver malfunctions renal impairment high parasitemia (>500,000/mm 3 )

5 Cerebral Malaria severe complication of falciparum malaria mortality of 30-50% a diffuse encephalopathy with loss of consciousness severe headache followed by drowsiness, confusion and coma consciousness ranges from stupor to coma unresponsive to pain, visual, and verbal stimuli convulsions frequently observed onset can be gradual or sudden associated with sequestration in micro- vasculature of brain

6 P. falciparum expresses ‘knobs’ on the surface of infected erythrocytes. Knobs mediate cytoadherence to endothelial cells.

7 Several Parasite Proteins Are Associated with Knobs KAHRP and PfEMP2 are believed to interact with the submembrane cytoskeleton of the host erythrocyte reorganization of the membrane skeleton may result in knob formation PfEMP1 crosses the erythrocyte membrane and is exposed on the surface

8 family of var genes conserved intracellular C-terminus acidic terminal segment (ATS) binds cytoskeleton + KAHRP transmembrane domain variable extracellular domain composed of modules 2-7 copies of Duffy-binding like domains 5 sequence types (  ) 1-2 cys-rich interdomain regions all have DBL1  + CIDR participates in cytoadherence PfEMP-1 Structure

9 CD36 Ig super-family ICAM-1 VCAM-1 PECAM-1 E-selectin thrombospondin chondroitin sulfate A hyaluronic acid Rosetting Receptors CR-1 glycosaminoglycan blood group A Possible Host Receptors

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11 Sequestration Hypothesis cytoadherence  cerebral ischemia  hypoxia, metabolic effects  coma  death

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13 Problems with Sequestration Hypothesis rapid reversibility lack of ischemic damage low levels of permanent neurological damage sequestration occurs in non-cerebral malaria cases

14 Cytokine Theory

15 Cytokine Theory Problem minimal lymphocyte infil- tration or inflammation

16 Severe falciparum malaria potentially high parasitemias sequestration complex (and not fully understood) host-parasite interactions


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