Weproduced a transgenic rodent malaria parasite (Plasmodium berghei) that contained the luciferase gene under apromoter region of elongation factor-1α. These transgenic (TG) parasites expressed luciferase inall stages of their life cycle, as previously reported. However, we were the firstto succeed in observing sporozoites as a mass in mouse skin following theirdeposition by the probing of infective mosquitoes. Our transgenic parasites mayhave emitted stronger bioluminescence than previous TG parasites. The estimatednumbers of injected sporozoites by mosquitoes were between 34 and 775 (median 80). Since luciferase activity diminished immediately after the death of theparasites, luciferase activity could be an indicator of the existence of liveparasites. Our results indicated that sporozoites survived at the probed sitefor more than 42 hours. We also detected sporozoites in the liver within 15 minof the intravenous injection. Apart from the liver, bioluminescence was notobserved in the lung, kidney, or spleen. We reconfirmed that the liver was thefirst organ for malaria parasites to enter and increase in number.

We assessed the effectiveness of practical instruction in parasitology for undergraduates at Jichi Medical School by examining grades on a practical examination. Two hundred six second-year medical students in 1997 and 1998 (103 students in each year) were enrolled in this study. The students took written and practical examinations at the end of the program. We found that grades on the practical examination were correlated with grades on the written examination (r=0.5664; p<0.001). The discrimination index ranged from 0.23 to 0.78. The percentage of correctly identified species was significantly higher when students studied live specimens than when they used other methods (p<0.0001 in both 1997 and 1998). The highest rates of correct identification (more than 90%) were for Anisakis species larvae and Enterobius vermicularis eggs in 1997 and for Anisakis species larvae, E. vermicularis eggs, and Anopheles mosquitoes in 1998. Results of neither written nor practical examinations differed significantly between students who chose biology at the entrance examination and those who did not. Our results suggest that undergraduates would gain a better understanding of parasitology by studying live specimens.

We produced a transgenic rodent malaria parasite (Plasmodium berghei) that contained the luciferase gene under a promoter region of elongation factor-1α. These transgenic (TG) parasites expressed luciferase in all stages of their life cycle, as previously reported. However, we were the first to succeed in observing sporozoites as a mass in mouse skin following their deposition by the probing of infective mosquitoes. Our transgenic parasites may have emitted stronger bioluminescence than previous TG parasites. The estimated number of injected sporozoites by mosquitoes was between 34 and 775 (median 80). Since luciferase activity diminished immediately after the death of the parasites, luciferase activity could be an indicator of the existence of live parasites. Our results indicated that sporozoites survived at the probed site for more than 42 hours. We also detected sporozoites in the liver within 15 min of the intravenous injection. Bioluminescence was not observed in the lung, kidney or spleen. We confirmed the observation that the liver was the first organ in which malaria parasites entered and increased in number.