Experimental induction of nocardiosis in yellowtail, Seriola quinqueradiata Temminck & Schlegel by artificial challenge

• Published in: Journal of fish diseases Vol. 29; no. 9; pp. 529 - 534
• Main Authors: Itano, T, Kawakami, H, Kono, T, Sakai, M
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.09.2006
• Subjects: Animals; challenge methods; Colony Count, Microbial; Drug Administration Routes - veterinary; Fish Diseases - etiology; Fish Diseases - mortality; Lethal Dose 50; Marine; mortalities; Nocardia; Nocardia - pathogenicity; Nocardia Infections - etiology; Nocardia Infections - mortality; Nocardia Infections - veterinary; Nocardia seriolae; nocardiosis; Perciformes - microbiology; Seriola quinqueradiata; Survival Analysis; Time Factors; Water Microbiology; yellowtail
• ISSN: 0140-7775; 1365-2761
• DOI: 10.1111/j.1365-2761.2006.00748.x

Challenge methods for inducing nocardiosis, caused by Nocardia seriolae in yellowtail, Seriola quinqueradiata, were evaluated. The first method involved intraperitoneal injection of 1.1 × 102, × 103 and × 104 cfu of N. seriolae; the second was by bath immersion with three different concentrations of bacterial suspension for 10 min; the third was by intradermal injection using a multipuncture device; the fourth was by oral administration using a tube; the fifth was based on the co‐habitation of uninfected fish with others that had been artificially infected, i.e. intraperitoneally or by immersion for 10 min. The LD50 values for the infection trials were 1.9 × 102 (intraperitoneal injection), 1.5 × 104 mL−1 (immersion), 4.3 × 106 (intradermal injection) and 1.7 × 107 (oral administration). In the co‐habitation challenge, mortalities were 70% and 50% in groups of non‐infected fish mixed with fish infected by the i.p. injection and immersion methods, respectively. Fish challenged by intraperitoneal injection developed adhesions. Fish challenged by other methods did not show any gross clinical signs and moribund fish were similar to natural infection.