In Vitro Effects of High Temperatures on Avian Malarial Parasites

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Abstract
A heparinized physiol. saline-blood mixture, containing Plasmodium cathemerium, was drawn up into capillary pipettes. These were sealed by flame and placed in a water bath at 50[degree] C, The thermal death point of P. cathemerium was detd. to be 50[degree] C for 8 mins. A few parasites survived after exposure to this temp, for 7 min. but they evinced a prolonged incubation period when inoculated into animals. 3 strains of P. cathemerium (3H1-3, 3H1-4, 3H1-5) were isolated from strain 3H1-2 in this manner. During the periodicity study, the parasites of strain 3H1-3 exhibited marked disturbance of synchronism in the production of both asexual and sexual parasites. 7 months later this strain had returned to normal. The parasites of strain 3H1-4 had almost lost their power of gametocyte production during the periodicity study. There was a concomitant loss of periodicity in asexual reproduction. In the subsequent studies, this strain did not produce gametocytes and was incapable of infecting mosquitoes. Its asynchronism of reproduction remained unchanged. Strain 3H1-5 demonstrated no change from the parent strain in the characteristics investigated. Two effects of crisis on the periodicity of the infection were: a) delay in segmentation, and b) loss of synchronism during the crisis. These effects, not necessarily concomitant, might occur separately or simultaneously. Similar effects were noted just before the death of the host. When the synchronism of the asexual cycle was disturbed by a crisis, the synchronism of the gametocyte production was also disturbed.