Studies on resistance of Schistosoma to praziquantel(ⅩⅦ) Biological characteris- tics of praziquantel-resistant isolates of Schistosoma japonicum in mice / 中国血吸虫病防治杂志

ABSTRACT

Objective To investigate the biological characteristics of the praziquantel-resistant isolate of Schistosoma japoni-cum in mice,so as to explore the pathogenicity to definitive hosts and transmission intensity of the praziquantel-resistant isolate of S. japonicum. Methods Mice were infected with the cercariae released from two praziquantel-resistant isolates and two pra-ziquantel-susceptible isolates of S. japonicum. The mouse-Oncomelania hupensis snail-mouse cycle was established and main- tained in the laboratory. The prepatent period of parasite eggs,egg production,egg distribution in mice,parasite susceptibility to mice and egg size were investigated in each parasite isolate. Results The prepatent period of parasite eggs,egg counts in mouse feces,adult worms recovered from each mouse,egg counts in mouse tissues,egg counts in the mouse liver,and egg counts in intestine tissues were 36.1 d and 36.8 d ( t=0.907, P=0.372 ) , 14.6 / 100 mg and 21.2 / 100 mg (t=2.946, P=0.007),20.5 and 25.1 worms per mouse(t=2.128, P=0.042),31303 and 38594 per paired adult worm(t=2.185, P=0.04),14810 and 19715 per paired adult worm(t=2.934, P=0.007),and 16493 and 18879 per paired adult worm(t=1.044, P=0.309)in the mice infected with Jiangsu praziquantel-susceptible and-resistant isolates of S. japonicum, respectively,and there were no significant differences between Jiangsu praziquantel-susceptible and-resistant isolates of S. ja-ponicum in the length of paired adult worms(t=0.328, P=0.744),female adult worms(t=0.386, P=0.701)or male adult worms(t=0.332, P=0.741). The prepatent period of parasite eggs,egg counts in mouse feces,adult worms recovered from each mouse,egg counts in mouse tissues,egg counts in the mouse liver,and egg counts in intestine tissues were 35.5 d and 35.6 d(t=0.169, P=0.867),13.3/100 mg and 18.9/100 mg(t=3.622, P=0.001),17.6 and 25.1 worms per mouse(t=3.153, P=0.004),30932 and 53903 per paired adult worm(t=3.865, P=0.001),12307 and 26363 per paired adult worm (t=4.388, P<0.01),and 18625 and 27541 per paired adult worm(t=2.679, P=0.012)in the mice infected with Hunan praziquantel-susceptible and-resistant isolates of S. japonicum,respectively,and there were no significant differences between Hunan praziquantel - susceptible and - resistant isolates of S. japonicum in the length of paired adult worms (t=0.853, P=0.397),female adult worms(t=0.573, P=0.569)or male adult worms(t=0.742, P=0.461). Conclusions The praziquantel-resistant isolate of S. japonicum has a higher parasite egg production and more eggs deposited in the mouse liver than drug-susceptible isolate,suggesting that the praziquantel-resistant isolate of S. japonicum exhibits a greater pathogenicity to definitive hosts. In addition,more parasite eggs are detected in the feces of mice infected with the praziquantel-resistant isolate of S. japonicum relative to the drug-susceptible isolate,indicating that the praziquantel-resistant isolate of S. japonicum exhibits a greater transmissibility than the drug-susceptible isolate.