Plasmodium chabaudi: Effect of antimalarial drugs on gametocytogenesis

Buckling, A., Crooks, L., and Read A. 1999. Plasmodium chabaudi: Effect of antimalarial drugs on gametocytogenesis. Experimental Parasitology 93, 45-5 4. The proportion of asexual blood-stage malaria parasites that develop int o transmission stages (gametocytes) can increase in response to stress. We investigated whether stress imposed by a variety of antimalarial drugs admi nistered before or during infection increased gametocyte production (gameto cytogenesis) in vivo in the rodent malaria parasite, Plasmodium chabaudi. A ll methods of drug treatment greatly reduced the numbers of asexual parasit es produced during an infection but resulted in either no reduction in numb ers of gametocytes or a smaller reduction than that experienced by asexuals , We used a simple model to estimate temporal variation in gametocyte produ ction. Temporal patterns of gametocytogenesis did not greatly differ betwee n untreated and prophylaxis infections, with rates of gametocytogenesis alw ays increasing as the infection progressed. In contrast, administration of drugs 5 days after infection stimulated increased rates of gametocytogenesi s early in the infection, resulting in earlier peak gametocyte densities re lative to untreated infections. Given the correlation between gametocyte de nsities and infectivity to mosquito vectors, and the high frequency of subc urative drug therapy and prophylaxis in human populations, these data sugge st that antimalarial drugs may frequently have only a small effect on reduc ing malaria transmission and may help to explain the rapid spread of drug-r esistant genotypes. (C) 1999 Academic Press.