Malaria: Protozoa II Flashcards
Malaria is caused by 4 Plasodium
- P. Malariae
- P. Ovale
- P. Vivax
- P. Falciparum
Malaria life cycle in 2 organisms
- mosquito (sexual cycle)
2. Human (asexual cycle)
Malaria life cycle
- Infected mosquito bites human; sporozoites migrate through bloodstream to liver of human
- sporozoites undergo schizogony in liver cells; merozoites are produced
- Merezoites released into bloodstream from liver infects new RBC
- Merezoite develops rings stage in RBC
- Ring stage grows and divides producing mereozoites
- Merozoites are released when RBC ruptures; some merozoites infect new RBC, some develop into male and female gametocytes
- Another mosquito bites infected human and ingests gametocytes
- In mosquito digestive tract, gametocytes unite to form zygot
- Resulting sporozoites migrate to salivary glands of mosquito
Malaria: Exoerythrocytic Schizogony
- hepatocyte invasion
- asexual replication
- no overt pathology
relapse
hypnozoite
recrudenscence
subpatent
Erythrocytic stage
- intracellular parasite undergoes trophic phase
- young trophozoite called ‘ring form’
- ingest host haemoglobine
Erythrocytic Schizogony
- nuclear division
- erythrocyte ruptures releasing merozoites
- blood stage results in disease symptoms
Malaria clinical features is characterised by
acute febrile attacks (malaria paroxysms)
Manifestations and severity depends on
species and host status: immunity, health, nutritional state, genetics
recrudescences and relapses can occure over
months or years
Paroxysms associated with
synchrony of merozoite release
Falciparum is different
may not exhibit classic paroxysms and thus has continous fever
Gametogenesis occurs in
mosquito gut.
- Exflagellation most obvious
- gametocyte activating factor in mosquito
Sporogony
occurs in mosquito
- fusion of micro and macrogrametes
- zygote–>ookinete
- ookinete transverses gut epithelium
Invasive stages
- Merozoite: erythrocyte
- Sporozoite: salivary glands and hepatocytes
- Ookinete: epithelium
P. vivax causes
- benign tertian malaria
- fever paroxysms recur every 48 hrs
- relapses up to several yrs
P. falciparum causes
- malignant tertian malarai
- fever paroxysms recur every 48 hours
- true relapses do not occur
- most virulent in humans
- greatest killer of humanity
P. malariae causes
- quartan malaria
- fever paroxysms recur every 72 hrs
- relapses up to several decades
- transfusion malaria
P. ovale causes
- milk tertian malaria
- fever paroxysms recur every 48 hrs
- rarest malaria