Abstract
The effect of exposure to high temperature on the fertilization stage and the sporogonic stage of rodent malaria, Plasmodium berghei and P. yoelii, was studied in vivo and in vitro. It has been recommended that P. berghei-infected mosquitoes needs to be maintained at a temperature of about 21C, but P. yoelii-infected mosquitoes can be reared at normal insectary temperature (24-27C). We found that exposure meal remarkably impeded the development of both P. berghei and P. yoelii in the mosquitoes. The damaging effect occurred by the exposure to 26C from 0-30 min in P. berghei and from 0-180 min in P. yoelii after the blood meal. Exflagellation and resulting ookinete formation of P. berghei, in vitro, were also impaired by exposure to 26C for the first 30 min of incubation. Exflagellation in P. yoelii was not impaired at 26C but was impaired at 31C. These results indicate that exposure to low temperature is essential for transformation of malaria parasites in mosquito stage, and each species of Plasmodium has an appropriate low temperature as a trigger for the transformation.