THE ADJUSTMENT OF THE SCHIZOGONIC CYCLE OF PLASMODIUM-CHABAUDI-CHABAUDI IN THE BLOOD TO THE CIRCADIAN-RHYTHM OF THE HOST

Experiments were performed with P. chabaudi chabaudi to investigate th e relationship between the development of the parasite and the circadi an rhythm of the host. Blood was taken from a donor mouse at 10.00 hou rs, when it contained mainly young stages and inoculated to receptor m ice, either immediately or after 8 hours at +4-degrees-C. The inoculum was diluted in order to obtain a more or less extended prepatent peri od. Thus, by using successively the different mice, parasitemias could be followed during 12 days before the crisis. When parasitemias reach ed 1%, from day 1 (D1) to D7, depending on the dilution, the parasitic patterns were studied every 6 hours during 2 or 3 days. In mice inocu lated at 10.00 hours the rhythm remained unmodified. In mice inoculate d at 18.00 hours the infection was at first synchronous (from D1 to D4 ) but the schizogony occurred between 06.00 and 12.00 hours instead of midnight. From day 4 to day 7 the infection became asynchronous. At d ay 10 the normal rhythm was resumed and the schizogony occurred around midnight.