Specific PCR for Myxobolus arcticus SSU rDNA in juvenile sockeye salmon Oncorhynchus nerka from British Columbia, Canada

Abstract

A PCR for the specific detection of the salmon brain parasite Myxobolus arcticus (Pugachev and Khokhlov, 1979) was developed using primers designed to amplify a 1363 base pair fragment of the small subunit rDNA. The assay did not amplify DNA from 5 other Myxobolus species or from 7 other myxozoan species belonging to 5 other genera. For juvenile sockeye salmon Oncorhynchus nerka (Walbaum) collected from Chilko Lake, British Columbia (BC), Canada, in 2011, the prevalence by PCR was 96%, in contrast to 71% by histological examination of brain tissue. In 2010, the histological prevalence was 52.5%. Sequence identity between M. arcticus from Chilko Lake and other sites in BC ranged from 99.7 to 99.8% and was 99.6% for a Japanese sequence. In contrast, an M. arcticus sequence from Norway shared 95.3% identity with the Chilko Lake sequence, suggesting misidentification of the parasite. Chilko Lake sockeye salmon were previously reported free of infection with M. arcticus, and more research is required to understand the processes involved in the local and global dispersion of this parasite.

Myxobolus arcticus and Parvicapsula minibicornis infections in sockeye salmon Oncorhynchus nerka following downstream migration in British Columbia

“…2 for zone definitions); n = number tested; PCR+: number positive by polymerase chain reaction the anterior spinal cord or hindbrain of sockeye salmon that elicits negligible overt pathology. Our finding of M. arcticus in 27 to 66% of juvenile Fraser River sockeye collected from the Strait of Georgia over 3 yr was consistent with Mahony et al (2015), who reported the parasite in 53 and 71% of histological brain preparations from juvenile sockeye salmon collected at the Chilko Lake smolt fence in 2010 and 2011, respectively. Nearly all (96%) of the latter group were found to be infected by using PCR (Mahony et al 2015).…”

“…Our finding of M. arcticus in 27 to 66% of juvenile Fraser River sockeye collected from the Strait of Georgia over 3 yr was consistent with Mahony et al (2015), who reported the parasite in 53 and 71% of histological brain preparations from juvenile sockeye salmon collected at the Chilko Lake smolt fence in 2010 and 2011, respectively. Nearly all (96%) of the latter group were found to be infected by using PCR (Mahony et al 2015). There was no evidence in the present study for trends in the prevalence of M. arcticus among catch areas in the Strait of Georgia during the 6−8 wk residency of juvenile sockeye within the Strait of Georgia.…”

“…This is consistent with Bailey & Margolis (1987), who reported the parasite in 62.0 and 66.0% of smolts from Quesnel and Bowron Lakes, respectively. Interestingly, unlike In no year was n ≥ 10 for either parasite in spawning zone 1 here or in Mahony et al (2015), Bailey & Margolis (1987) found no evidence of the parasite in 244 juvenile sockeye sampled from Chilko Lake between 1976 and 1982. Evidently, the distribution of the parasite among natal lakes is not stable over decadal time scales.…”

“…The aqueous layer (~200 µl) was transferred to a new tube and DNA extracted using a DNeasy blood and tissue kit (Qiagen) as per the manufacturer's instructions. Myxobolus arcticus-specific DNA was amplified following Mahony et al (2015). Similarly, DNA was extracted from ethanol-preserved intestine or mid-kidney using the DNeasy Tissue kit, described above.…”

Development of a multiplex PCR method for the simultaneous detection of four myxosporeans infecting gibel carp Carassius auratus gibelio

“…However, this approach can be time-and laborconsuming, and detection and identification is mainly based on the mature spore stages, with the early parasite stages likely to be neglected (Grabner et al 2012, Mahony et al 2015. Immunological methods based on antibodies or lectins (Knaus & El-Matbouli 2005, Estensoro et al 2013) have also been developed.…”