title: Effect of size and temperature at vaccination on immunization and protection conferred by a live attenuated Francisella noatunensis immersion vaccine in red hybrid tilapia.
abstract: Francisella noatunensis subsp. orientalis (Fno) is a pleomorphic, facultative intracellular, Gram-negative, emerging bacterial pathogen of marine and fresh water fish with worldwide distribution. In this study, the efficacy of an attenuated Fno intracellular growth locus C (iglC) mutant was evaluated for use as a live immersion vaccine, when administered to hybrid tilapia at two different stages of growth (5 g fry and 10 g fingerlings) and at two temperatures (25 °C and 30 °C). To determine vaccine efficacy, mortality, days to first death, and Fno genome equivalents (GE) in the spleens of survivors, as well as serum and mucus antibody levels, were evaluated after 30 d in fish challenged with a wild type virulent strain. Both size and temperature at vaccination played an important role in immunization and protection. Fry vaccinated at 25 °C were not protected when compared to non-vaccinated fry at 25 °C (p = 0.870). In contrast, 5 g fry vaccinated at 30 °C were significantly protected compared to non-vaccinated fry at 30 °C (p = 0.038). Although lower mortalities occurred, 10 g fingerlings vaccinated at 25 °C were not protected, compared to non-vaccinated fingerlings at 25 °C (p = 0.328), while, 10 g fingerlings vaccinated at 30 °C were significantly protected, compared to non-vaccinated fingerlings at 30 °C (p = 0.038). Additionally, overall mortality of 5 g fish was significantly higher than in 10 g fish. Mortality was also significantly higher in fish subjected to a 30 to 25 °C temperature change one week prior to challenge, than in fish maintained at the same temperature during vaccination and challenge. This information demonstrates that both temperature and size at vaccination are important factors when implementing immunization prophylaxis in cultured tilapia.
authors.affiliation: Center for Conservation Medicine and Ecosystem Health, School of Veterinary Medicine, Ross University, Main Island Road, West Farm, Saint Kitts and Nevis. esoto@rossvet.edu.kn
authors.forename: Esteban
authors.initials: E
authors.lastname: Soto
authors.forename: Nicholas
authors.initials: N
authors.lastname: Brown
authors.forename: Zackarias O
authors.initials: ZO
authors.lastname: Gardenfors
authors.forename: Shaun
authors.initials: S
authors.lastname: Yount
authors.forename: Floyd
authors.initials: F
authors.lastname: Revan
authors.forename: Stewart
authors.initials: S
authors.lastname: Francis
authors.forename: Michael T
authors.initials: MT
authors.lastname: Kearney
authors.forename: Alvin
authors.initials: A
authors.lastname: Camus
mesh_terms: D000818:Animals; D001428:Bacterial Vaccines / Q000627:therapeutic use*; D049628:Body Size; D005393:Fish Diseases / Q000276:immunology / Q000517:prevention & control*; D005603:Francisella / Q000276:immunology*; D016905:Gram-Negative Bacterial Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D006652:Histological Techniques; D006824:Hybridization, Genetic / Q000235:genetics; D016014:Linear Models; D060888:Real-Time Polymerase Chain Reaction; D013154:Spleen / Q000382:microbiology; D013696:Temperature; D017210:Tilapia
chemical_list: D001428:Bacterial Vaccines