Persistence of Infection by Metacercariae of Apophallus sp., Neascus sp., and Nanophyetus salmincola Plus Two Myxozoans (Myxobolus insidiosus and Myxobolus fryeri) in Coho Salmon Oncorhynchus kisutch

Department of Microbiology, Oregon State University, Corvallis, Oregon 97331, USA.
Journal of Parasitology (Impact Factor: 1.23). 12/2009; 96(2):340-7. DOI: 10.1645/GE-2289.1
Source: PubMed


We evaluated the ability of 5 muscle- or skin-dwelling parasites to persist in naturally infected coho salmon, Oncorhynchus kisutch, from the West Fork Smith River, Oregon, by holding them in captivity from late summer to early spring (parr stage to the typical time of smoltification). These parasites included metacercariae of 3 digeneans, Nanophyetus salmincola, Apophallus sp., and neascus sp., and 2 myxozoans, Myxobolus insidiosus and Myxobolus fryeri. Two groups of wild-caught fish were evaluated in the laboratory, i.e., heavily infected fish from the lower main stem and less severely infected fish collected from tributaries of this river. All parasites survived in these fish for the 7-month experiment. Only 2 parasites had a statistically significant lower median abundance between host life stages. The mean abundance of N. salmincola declined 45% in the tributary fish and Apophallus sp. declined 43% in the lower main stem fish. However, more than 50% of each species persisted until the end of the study, with smolts still harboring relatively high infections.

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Available from: Jayde A Ferguson, Sep 02, 2015
    • "In both studies, parasite presence was limited to just 5 weeks postchallenge and by 9 weeks postchallenge was nearly nonexistent. The longevity of trematode metacercariae has been well studied for several parasite species and their respective fish hosts (Fischthal 1949; Hoffman 1950, 1956, 1958; Hoffman and Putz 1965; Lemly and Esch 1983; Ferguson et al. 2010; Boerlage et al. 2013). In general, metacercaria of digeneans persist for extended periods of time, maximizing the chance for transmission to the definitive host by extending the availability to opportunistic predation. "
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    • "Muscle and kidney samples were thawed and the entire amount of tissue weighed. We placed a subsample of muscle tissue (4.5–6.3 g) or the entire posterior kidney (0.02–0.24 g) between two pieces of Plexiglas with a small amount of water, and applied pressure to create a wet mount (Ferguson et al. 2010). We then examined the slide under a compound microscope to identify and enumerate parasites. "
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