Application of Non-Fluorescent Dyes to Assess the Antischistosomal Effect of Antimalarial Drugs on Schistosoma mansoni Adult Worms.

The possible emergence of praziquantel (PZQ)-tolerant and/or -resistant schistosomes requires the study and development of new antischistosomal drugs as alternatives to PZQ. The present study investigates the capability of 3 dyes-methylene blue (MB), neutral red (NR), and trypan blue (TB)-to assess the in vitro antischistosomal effect of antimalarial drugs on Schistosoma mansoni adult worms. S. mansoni adult worms were incubated in the medium alone as the control or in the medium supplemented with 10 μg/ml primaquine (PQ), artesunate (AR), or amodiaquine (AQ) for 5 days. Viabilities of the worms were observed following staining with MB, NR, or TB. The disparity of MB and NR staining among male and female adult worms treated with PQ, AR, and AQ correlated with the various levels of damage to the male and female worms. Furthermore, the severity of the damage to the adult worms treated with the 3 drugs appeared to be reflected in the TB staining status. The results indicate that the 3 non-fluorescent dyes can serve as useful complementary tools to assess the antischistosomal effect of antimalarial drugs.