Predation preference of the crayfish Procambarus clarkii on schistosomiasis transmitting snails: influence of snail species, infection status, and size.

backgroundSchistosomiasis control relies largely on preventive chemotherapy; however, rapid reinfection persists in many endemic settings due to continued transmission by freshwater snail intermediate hosts. Biological control using natural predators has been proposed as a complementary strategy to reduce vector snail populations. The invasive North American crayfish Procambarus clarkii, which preys on schistosome-transmitting snails, represents a promising candidate. However, the ecological and biological factors influencing predator-prey interactions between crayfish and intermediate snail hosts remain poorly understood.

methodsWe evaluated the predatory potential of Procambarus clarkii on schistosomiasis-transmitting snails under controlled laboratory conditions. Aquarium-based experiments assessed the effects of snail species, infection status, prey size, and crayfish developmental stage on predation dynamics. Predation outcomes were quantified using cumulative predation and time-to-depletion analyses and analysed using exact binomial tests, Fisher's exact tests, generalized linear models (GLMs), and paired Wilcoxon signed-rank tests.

resultsIn early-time cumulative predation analysis, infected snails were consumed more frequently than uninfected snails (64.3% vs. 35.7%; exact binomial test, p = 0.044). Time-to-depletion analysis also showed earlier clearance of infected snails (median 18 h vs. 20 h; paired Wilcoxon signed-rank test, p = 0.002). Predation did not differ significantly between snail species (p = 0.37), indicating no evidence of species-specific prey selection. Crayfish exhibited size-dependent predation, preferentially consuming larger snails (7-12 mm) over smaller snails (< 6 mm; p = 0.04), with no significant differences observed among larger size classes (p = 0.44). In predator-prey stage experiments, adult crayfish consumed similar proportions of adult and juvenile snails (82.8% vs. 80.6%), whereas juvenile crayfish consumed significantly more juvenile than adult snails (63/180 vs. 10/180; p < 0.001).

conclusionPredation by Procambarus clarkii was influenced by prey size and infection status rather than species identity. The preferential removal of infected and larger snails provides experimental evidence for the potential of crayfish as a complementary biological control agent within integrated schistosomiasis control strategies.