Influence of the host photoperiodicity on the schizogonic cycle and the synchronism of the rodent malaria parasite Plasmodium chabaudi chabaudi

This study intended to determine whether LD (Light:Dark) regimens different from the usual 12:12 hours could impair the schizogonic cycle and the sync hronism of the rodent malaria parasite Plasmodium chabaudi chabaudi. Five i llumination regimens of 12:12 LD, 5:5 LD, 18:18 LD, DD (constant dark) and LL (constant light) were used. Mice were kept in these regimens three month s prior to and throughout the experiment. The total and the differential pa rasitaemia were checked every hour, during more than 24 hours. The parasita emia data indicated that changes in the LD regimen, except for the LD 18:18 , do not affect the length of the developmental cycle of this malaria paras ite which remains 24 hours. In both the LL and 18:18 LD regimens, the synch ronisation of parasites were impaired, mostly in the LL regimen. Also, we n oticed that the schizogony which usually occurs in the dark part of the cyc le may happen in the light part too. A circadian rhythm in the frequency of the schizogonic cycle and a time dependent occurrence of ring forms, troph ozoites and schizonts were observed. Al high parasitaemia, the infection wa s desynchronised. The total parasitaemia curves displayed a plateau region, followed by a drop at the end of the plateau, and an increase after the sc hizogony to reach the next plateau level.