Microinvertebrate consumption rates of Fasciola hepatica miracidia are not affected by alternate food

The liver fluke (Fasciola hepatica) is a significant parasite of the global livestock industry, leading to negative economic and animal welfare impacts. Control of F. hepatica is becoming increasingly difficult as many liver fluke populations are developing resistance to commonly used anthelmintics. Additional or alternate control methods are, therefore, required. Microinvertebrates such as those of the order Cyclopoida and subclass Ostracoda are common organisms found in the same aquatic habitats as F. hepatica's intermediate snail host. We explore whether these microinvertebrates are effective predators of F. hepatica miracidia. We experimentally determined a) the consumption rates of miracidia by the two microinvertebrate groups, b) the form of functional feeding response displayed by each and c) whether inclusion of an alternate food source altered miracidial predation patterns. We find that cyclopoids and ostracods feed on miracidia and that where a statistically supported fit was found, the functional feeding response for both microinvertebrates was type II. Further, miracidial consumption by either microinvertebrate did not decline significantly in the presence of alternate prey. Our results suggest that cyclopoids and ostracods are both effective predators of F. hepatica and therefore have the potential as F. hepatica biocontrol agents. An important next step will be to explore what impact such predation has on the infection dynamics of the adult fluke in the definitive host.