Range expansion and molecular confirmation of the Asian fish tapeworm in the lower Great Lakes and St. Lawrence River with notes on infections in baitfish

The Asian fish tapeworm, Schyzocotyle (formerly Bothriocephalus) acheilognathi, was surveyed in fishes from the lower Great Lakes, surrounding waters, and St. Lawrence River between 2009 and 2015. Sequences of the internal transcribed spacer region (ITS1, 5.8S, ITS-2) and the barcode gene cytochrome oxidase 1 (CO1) are provided, confirming identification. Emerald shiners (Notropis atherinoides) collected in 2009-10 from the St. Clair River, the Detroit River, Lake Erie, the Niagara River, and Lake Ontario were infected at most localities with prevalence ranging from 1.9 to 20.0%. Infection intensity was negatively correlated with condition in these emerald shiners. Museum specimens of emerald shiners collected in 2007 from Lake Erie and vicinity also were infected at a prevalence of 5.0%. The parasite was observed for the first time in the St. Lawrence River at Beauharnois, QC, in a bluntnose minnow (Pimephales notatus) in June 2012. Subsequent infections in the St. Lawrence River were observed in two bluntnose minnows from Beauharnois in September 2012 and in emerald shiners from Beauharnois (prevalence = 12.0%) in June 2013, at Îles de la Paix, QC (prevalence = 6.7%) and Îles de Boucherville, QC (prevalence = 2.8%) in September 2013, and Îlet Vert, QC (prevalence = 1.8%) east of Montreal in September 2015. Samples of six other fish species from the Great Lakes, eight from surrounding small lakes and rivers, and eight species from the St. Lawrence River were uninfected. Of six species collected from six bait retailers along the north shore of Lake Erie and Lake Ontario, emerald shiners were infected at prevalences of 4.0 and 20.0% at two facilities out of six, indicating that infected baitfish have occurred in the wild at some harvest sites with sufficient prevalence to be transferred throughout the commercial supply chain. Results demonstrate that the Asian fish tapeworm has spread rapidly across the lower Great Lakes since its first observation in the Detroit River in 2002 and appears to be spreading eastward from its recent initial capture location in the St. Lawrence River.