Application of real-time PCR for specific detection of Lepeophtheirus salmonis in fluid samples from lumpfish (Cyclopterus lumpus) stomachs

The Norwegian Food Safety Authority recently stated that stomach flushing is
in violation of the Animal Welfare Act. The objective of our research was to develop a
genetic method for the routine identification of Lepeophtheirus salmonis in stomach fluid
samples taken through the mouth of lumpfish. The established method was based on a
previously published real-time PCR assay targeting the mitochondrial cytochrome oxidase I (mtCOI) gene in L. salmonis. Lumpfish were fed with L. salmonis, then captured
upon ingestion and subsequently transferred to an incubation tank. The method was used
to test 62 fluid samples collected during the first, second and third days post L. salmonis
consumption. No DNA extraction or purification was used prior to the real-time PCR.
The results were compared with visual examination subsequent to dissection. Visual
identification was able to identify 51 L. salmonis (82%) whereas real-time PCR was able
to detect 59 L. salmonis (95%) out of the 62 examined samples. The results indicate that
real-time PCR assays can be used for specific detection of L. salmonis in fluid samples
from the stomach of lumpfish. Furthermore, our study demonstrates that the PCR assay
offers a reliable non-lethal alternative to dissection or stomach flushing and the subsequent
visual identification of L. salmonis.