Broader Geographic Sampling Increases Extent of Intermediate Host Specificity for a Trematode Parasite...

Knowledge of helminth life cycles is essential to understanding their host specificity, geographic distribution, and transmission. Many helminth life cycle descriptions are based on field collections in a limited part of the parasite's range. However, it is important to determine whether helminth life cycles and host specificity remain consistent across their geographic range so that we may better understand their life history and transmission ecology. Here, we investigated whether the life cycle of a widespread trematode, Quinqueserialis quinqueserialis (Notocotylidae) varies across its geographic range. Four species of planorbid snails; Gyraulus circumstriatus, Gyraulus crista, Planorbula sp., and Promenetus exacuous, were collected at 5 locations in Canada (3 in Manitoba, 2 in Northwest Territories). Snails and parasite larvae were morphologically and genetically identified to species. The total prevalence of Q. quinqueserialis infections in snail hosts among the 5 locations was 2.3% (n = 1,017). Three species of snails were infected with Q. quinqueserialis rediae: G. circumstriatus, G. crista, and P. exacuous. Two of the 3 species of snails were infected in central (Manitoba) and northern locations (Northwest Territories) within Canada, which indicates limited life cycle variation across a large geographic range. This is the first report of snails naturally infected with Q. quinqueserialis in Canada. These novel host records demonstrate that this trematode species is not as host-specific for first intermediate host species as previously described.