Praziquantel-induced tegumental damage in vitro is diminished in schistosomes derived from praziquantel-resistant infections

The aggressive use of praziquantel to combat schistosomiasis in Egpyt raise s concern about the possible emergence of resistance. Eggs from Egyptian pa tients with praziquantel-resistant infections (not cured by doses of praziq uantel) have been used to establish infection-specific schistosome isolates in mice. The response of these worms to the drug was observed in vitro, in order to determine if the isolates obtained from these resistant infection s were. in fact, less responsive to praziquantel. One of the hallmark effec ts of praziquantel on schistosomes in vitro is a disruption of the worm's o uter surface, the tegument. Here, praziquantel-induced tegumental damage is observed in 3 distinct isolates, 2 derived from resistant infections and 1 from an infection cured by a single dose. The isolates from the resistant infections were less susceptible to praziquantel-induced tegumental damage in vitro, suggesting that the norms are in some way less responsive to the drug.