Susceptibility of human Plasmodium knowlesi infections to anti-malarials.
BACKGROUND
Evidence suggests that Plasmodium knowlesi malaria in Sarawak, Malaysian Borneo remains zoonotic, meaning anti-malarial drug resistance is unlikely to have developed in the absence of drug selection pressure. Therefore, adequate response to available anti-malarial treatments is assumed.


METHODS
Here the ex vivo sensitivity of human P. knowlesi isolates in Malaysian Borneo were studied, using a WHO schizont maturation assay modified to accommodate the quotidian life cycle of this parasite. The in vitro sensitivities of P. knowlesi H strain adapted from a primate infection to in vitro culture (by measuring the production of Plasmodium lactate dehydrogenase) were also examined together with some assays using Plasmodium falciparum and Plasmodium vivax.


RESULTS
Plasmodium knowlesi is uniformly highly sensitive to artemisinins, variably and moderately sensitive to chloroquine, and less sensitive to mefloquine.


CONCLUSIONS
Taken together with reports of clinical failures when P. knowlesi is treated with mefloquine, the data suggest that caution is required if using mefloquine in prevention or treatment of P. knowlesi infections, until further studies are undertaken.
Farrah A
FA
Fatih
Henry M
HM
Staines
Angela
A
Siner
Mohammed Atique
MA
Ahmed
Lu Chan
LC
Woon
Erica M
EM
Pasini
Clemens Hm
CH
Kocken
Balbir
B
Singh
Janet
J
Cox-Singh
Division of Clinical Sciences, Centre for Infection and Immunity, St, George's, University of London, London SW17 0RE, UK. s.krishna@sgul.ac.uk.
Sanjeev
S
Krishna
D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D037621:Artemisinins / Q000494:pharmacology; D001893:Borneo; D002738:Chloroquine / Q000494:pharmacology; D006801:Humans; D008288:Malaria / Q000469:parasitology*; D015767:Mefloquine / Q000494:pharmacology*; D021261:Parasitic Sensitivity Tests; D010963:Plasmodium falciparum / Q000187:drug effects / Q000302:isolation & purification; D016790:Plasmodium knowlesi / Q000187:drug effects* / Q000302:isolation & purification; D010966:Plasmodium vivax / Q000187:drug effects / Q000302:isolation & purification; D015047:Zoonoses / Q000469:parasitology
D000962:Antimalarials; D037621:Artemisinins; D002738:Chloroquine; D015767:Mefloquine