Evaluation of a nondestructive diagnostic test for Kudoa thyrsites in farmed Atlantic salmon (Salmo salar)

A nondestructive, inexpensive diagnostic test for the detection of Kudoa thyrsites infection in the musculature of Atlantic salmon (Salmo salar) was evaluated. The results indicated that the presence or absence of K. thyrsites in the hyohyoideus ventralis muscle of the operculum, as detected in wet-mount preparations, is a good indicator of the presence or absence of the parasite in the body musculature (fillets). The sensitivity and specificity of the diagnostic test were 79.0 and 94.6%, respectively. The sensitivity of the test was increased to 93% when the test was used to detect only heavily infected fillets: the presence or absence of K. thyrsites spores in the hyohyoideus ventralis muscle is slightly less accurate at detecting fillets with lighter infections of K. thyrsites.