PCR-RFLP: a targeted method to reveal host specific malacosporean infection profiles (Cnidaria: Myxozoa: Malacosporea)

Abstract

Malacosporeans are a group of endoparasitic cnidarians (Myxozoa) that use freshwater bryozoans and fish as final and intermediate hosts, respectively. The malacosporean Tetracapsuloides bryosalmonae causes proliferative kidney disease (PKD), an emerging disease in aquaculture and wild fish populations, including threatened salmonids in Europe and the USA. Mixed infections of malacosporeans are often encountered, and a monitoring tool for screening of multiple malacosporean species in either their fish or bryozoan hosts is therefore desirable. We describe an inexpensive method that combines PCR amplification of the partial 18S rRNA gene (~260 bp) and a single-step restriction fragment length polymorphism (RFLP) method for identification of 10 malacosporean lineages and species. We demonstrate and test this methodology on a set of DNA extracted from malacosporeans infecting fish kidney and tissues sampled from bryozoan colonies and compare the results with Sanger sequencing of the same parasite DNA isolates. The PCR-RFLP and Sanger sequencing methods agreed in 100% of cases. The PCR-RFLP method offers a number of opportunities, including screening large panels of host tissue samples to gain insights into infection patterns, characterizing mixed infections, and confirming highly pathogenic T. bryosalmonae infections. The method can also be further refined as new sequence data become available for malacosporeans.

Mitigating human impacts including climate change on proliferative kidney disease in salmonids of running waters

“…Independent of whether salmonids as the grayling and the rainbow trout might be dead end hosts for (the European strain of) T. bryosalmonae , the parasite does still infect these salmonids and cause disease. Native species that have been found susceptible to T. bryosalmonae infections in the wild are for Europe: brown trout ( Salmo trutta : Wahli et al., 2002), Atlantic salmon ( Salmo salar : Feist et al., 2002; Lauringson et al., 2021; Sterud et al., 2007), Arctic charr ( Salvelinus alpinus : Kristmundsson et al., 2010; Mo & Jørgensen, 2017; Svavarsdottir et al., 2021), European grayling ( Thymallus thymallus : Feist & Bucke, 1993; Vasemägi et al., 2017; Wahli et al., 2002) and European whitefish ( Coregonus lavaretus : Sobocinski et al., 2018); and for North America: rainbow trout ( Oncorhynchus mykiss : Hutchins et al., 2018b; Ruggeri et al., 2020), Chinook salmon ( Oncorhynchus tshawytscha : Hutchins et al., 2018b), Cutthroat trout (Henderson & Okamura, 2004; Oncorhynchus clarkii : Macconnell & Peterson, 1992), pink salmon ( Oncorhynchus gorbuscha : Braden et al., 2010), brook trout, Arctic charr ( Salvelinus alpinus : Brown et al., 1991) and, for example, mountain whitefish in the Yellowstone River ( Prosopium williamsoni : Hutchins et al., 2018b).…”