Copepod consumption by amphibians and fish with implications for transmission of species.

Parasitic nematodes in the genus have a complex life cycle that requires more than one host species in both aquatic and terrestrial habitats. The most well-studied species, , is the causative agent of human Guinea worm disease (dracunculiasis). There are several other species that infect non-human animals, primarily wildlife (reptiles and mammals). The classic route of transmission to humans is through the ingestion of water containing the intermediate host, a cyclopoid copepod, infected with third-stage larvae (L3s). However, many animal hosts (e.g., terrestrial snakes, dogs) of other sp. appear unlikely to ingest a large number of copepods while drinking. Therefore, alternative routes of infection (e.g., paratenic or transport hosts) may facilitate transmission to these species. To better understand the role of paratenic and transport hosts in transmission to animal definitive hosts, we compared copepod ingestion rates for aquatic species (fish, frogs [tadpoles and adults], and newts) which may serve as paratenic or transport hosts. We hypothesized that fish would consume more copepods than amphibians. Our findings confirm that African clawed frogs () and fish consume copepods, but that fish ingest, on average, significantly higher numbers (68% [34/50]) than adult African clawed frogs (36% [18/50]) during a 24-h time period. Our results suggest that amphibians and fish may play a role in the transmission of to definitive hosts. Still, additional research is required to determine whether, in the wild, fish or frogs are serving as paratenic or transport hosts. If so, they may facilitate transmission. However, if these animals simply act as dead-end hosts or as means of copepod population control, they may decrease transmission.