Non‐lethal sampling for the detection of Renibacterium salmoninarum by qPCR for diagnosis of bacterial kidney disease

• Published in: Journal of fish diseases Vol. 45; no. 6; pp. 883 - 894
• Main Authors: Jansson, Eva, Aspán, Anna, Comin, Arianna, Hjort, Maj, Jinnerot, Tomas, Axén, Charlotte
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.06.2022; John Wiley and Sons Inc
• Subjects: Animals; Aquaculture; Bacterial Infections; bacterial kidney disease; Bayes Theorem; Bayesian analysis; Bayesian Latent Class Analysis; Bayesian theory; BKD; Breeding; Detection; diagnostics; disease prevention; Disease prophylaxis; ELISA; farms; Female; Fish; Fish conservation; Fish Diseases - diagnosis; Fish Diseases - microbiology; Husbandry diseases; In vivo methods and tests; Kidney - microbiology; Kidney diseases; Kidney Diseases - diagnosis; Kidney Diseases - microbiology; Kidney Diseases - veterinary; Kidneys; Latent class analysis; Male; Microbiological strains; Micrococcaceae - genetics; monitoring; non‐lethal sampling; notifiable disease; Nucleotide sequence; p57 Protein; PCR; Probability theory; Prophylaxis; quantitative polymerase chain reaction; Real-Time Polymerase Chain Reaction - veterinary; Renibacterium; Renibacterium salmoninarum; Restoration; Salmonidae; Sampling; Sensitivity analysis; Surveillance; Sweden; Sweden; non-lethal sampling; diagnostics; BKD; Bayesian Latent Class Analysis; Renibacterium salmoninarum
• ISSN: 0140-7775; 1365-2761; 1365-2761
• DOI: 10.1111/jfd.13614

Bacterial kidney disease (BKD), caused by Renibacterium salmoninarum (Rs), can be transmitted both horizontally and vertically and there is no available cure or prophylaxis. The control of BKD requires continuous surveillance, which is challenging in aquaculture as well as in programs for conservation and restoration of salmonid fish strains. BKD is a notifiable disease in Sweden and is monitored through the mandatory health control program using a polyclonal ELISA for detection of the Rs p57 protein in kidney. Fish must be killed for sampling, an obvious disadvantage especially regarding valuable broodfish. The present study shows that gill‐/cloacal swabs collected in vivo for real‐time PCR (qPCRgc), allow a sensitive and specific detection of Rs. The sensitivity of qPCRgc was estimated to 97.8% (credible interval (ci) 93.8%–100%) compared to 98.3% (ci 92.7%–100%) and 48.8% (ci 38.8%–58.8%) of kidney samples for qPCR (qPCRk) and ELISA (ELISAk) respectively, by use of the Bayesian Latent Class Analysis (BLCA). Since the goal of the program is eradication of BKD the most sensitive test is preferrable. Using qPCRgc instead of ELISAk will result in a lower false negative rate and can be useful for surveillance in aquaculture and in breeding programs with valuable fish. However, a higher false positive rate warrants confirmatory lethal testing before a previously Rs negative farm is subject to restrictions.