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Comparing the malaria species

Comparing the malaria species
  Plasmodium falciparum Plasmodium vivax Plasmodium ovale Plasmodium malariae Plasmodium knowlesi[1-7]
Geography Tropical, temperate zones Tropical, temperate zones, absent from West Africa Tropical, endemic in West Africa, present in Philippines, Indonesia, and Papua New Guinea Tropical, isolated pockets Southeast Asia
RBC preference RBCs of all ages Young RBCs (reticulocytes) Young RBCs (reticulocytes) Older RBCs RBCs of all ages
Infected RBC diameter Normal Larger than normal Larger than normal Normal or smaller than normal Normal
Ameboid trophozoites No Yes Yes No No
Band forms No No No Yes Yes
Schizont* 16 to 20 merozoites; very rare in peripheral circulation 20 to 24 merozoites 4 to 16 merozoites (8 typical) 6 to 12 merozoites (8 or 10 typical) 8 to 16 merozoites (10 typical)
Parasitemia Can be very high Usually <2% Usually <2% Usually very low Can be high
Disease severity End organ damage and death can occur End organ damage and death less common than P. falciparum but can occur Severe disease uncommon Severe disease rare Severe disease can occur
Chloroquine resistance Yes Yes No Rare No
Relapses from liver No Yes Yes No No
Incubation period 12 days (8 to 25) 14 days (8 to 25; occasionally months) 15 days (9 to 17) 18 days (15 to 30; occasionally months to years) 11 days (9 to 12)
Prepatent period 11 days 12 daysΔ 12 days 32 days Uncertain in naturally infected humans
Cycle in red cell 48 hours 48 hours 48 hours 72 hours 24 hours

RBC: red blood cell.

* Identification of a schizont with >12 merozoites in the peripheral circulation is an important diagnostic clue for P. vivax. In general, schizonts of P. falciparum are very rarely seen in blood films; they occur only in the setting of severe disease with hyperparasitemia.

¶ The prepatent period is the time from mosquito bite to the first appearance of parasites in the peripheral blood (as detected by microscopy).

Δ The latency period of vivax is typically longer than falciparum (refer to UpToDate table summarizing time to symptoms for each species).
References:
  1. Shearer FM, Huang Z, Weiss DJ, et al. Estimating geographical variation in the risk of zoonotic Plasmodium knowlesi infection in countries eliminating malaria. PLoS Negl Trop Dis 2016; 10:e0004915.
  2. Lim C, Hansen E, DeSimone TM, et al. Expansion of host cellular niche can drive adaptation of a zoonotic malaria parasite to humans. Nat Commun 2013; 4:1638.
  3. Lee KS, Cox-Singh J, Singh B. Morphological features and differential counts of Plasmodium knowlesi parasites in naturally acquired human infections. Malar J 2009; 8:73.
  4. William T, Menon J, Rajahram G, et al. Severe Plasmodium knowlesi malaria in a tertiary care hospital, Sabah, Malaysia. Emerg Infect Dis 2011; 17:1248.
  5. Grigg MJ, William T, Menon J, et al. Artesunate-mefloquine versus chloroquine for treatment of uncomplicated Plasmodium knowlesi malaria in Malaysia (ACT KNOW): An open-label, randomised controlled trial. Lancet Infect Dis 2016; 16:180.
  6. Chin W, Contacos PG, Collins WE, et al. Experimental mosquito-transmission of Plasmodium knowlesi to man and monkey. Am J Trop Med Hyg 1968; 17:355.
  7. Coatney GR, Collins WE, Contacos PG. The Primate malarias. Division of Parasitic Diseases, Atlanta, GA 1971.
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