Lactococcus garvieae outbreaks in Brazilian farms Lactococcosis in Pseudoplatystoma sp. – development of an autogenous vaccine as a control strategy

Abstract

This study evaluated the control of streptococcosis outbreaks in Brazil, isolated from diseased sorubim and identified as Lactococcus garvieae by genetic sequencing. This report determined the potential for lactococcosis control in sorubim Pseudoplatystoma sp. with two vaccines: an aqueous-based, whole-cell inactivated vaccine (bacterin) and an oil-adjuvanted bacterin. Their efficacy was evaluated at 30 days post-vaccination (d.p.v.) by challenge with L. garvieae, and the antibody production response at 15, 30 and 60 d.p.v. and the non-specific immune response were compared amongst treatments. High protection levels (P < 0.05) were achieved with the oil-adjuvanted vaccine with a relative percentage survival value of 81.7% at 30 d.p.v. Additionally, the oil-adjuvanted vaccine increased the immunogenicity of the bacterin as indicated by greater agglutination antibody titres from 15 until 60 d.p.v. This is the first report of a positive effect of vaccine administration on the specific immunity of sorubim, and the study showed that a specific antibody plays an important role in sorubim defence against lactococcosis because the innate immune responses were similar in all of the studied animals. These results demonstrated that oil-adjuvanted vaccine can be an effective alternative for the protection of sorubim from L. garvieae disease.

Zebrafish as an alternative animal model in human and animal vaccination research

“…Among the immunological tests, the most frequent ones are: complete hematological analysis by counting erythrocytes; thrombocytes and leukocytes; differential white cell count; hematocrit; glucose; organ histology, and immunological essays such as serology, specific antibody titration, and agglutination [4,29,57]. Furthermore, toxicity tests can be also conducted using zebrafish such as embryotoxicity, hepatotoxicity, neurotoxicity, endocrine toxicity, genotoxicity, among others as proposed by Bailone et al [3].…”

Lactococcosis in Reared Fish in Brazil and Control Strategies

“…Neither clinical signs nor mortalities were observed in fish from the control groups during the experimental period. The study of Fukushima et al [6] represented the first record, from Brazil, of L.garvieae infection in commercial farms cultivating tropical catfish barred sorubim and hybrid sorubim. This pathogen is a classical etiologic agent, responsible for diseases in cold-water fish [3].…”

“…Fukushima et al [6] concluded that administration of the oiladjuvanted vaccine increased the level of specific antibodies and improved the agglutination ability and survival probability of sorubim exposed to live L. garvieae. These results also demonstrated that the oil-adjuvanted vaccine enhanced the potency and duration of protection against L. garvieae infection and, in the future, could offer an appropriate strategy to prevent these infections in Brazilian sorubim farms.…”

“…Five fish showing clinical signs of the disease were sampled from each farm and stored at 4°C prior to transport to a laboratory for bacteriological analysis. Were sampled aseptically by Fukushima et al [6] swabs of brain and kidney tissue from each fish, streaked onto 5% sheep blood agar, and incubated at 28°C for 72 h. Pure colonies were subjected to Gram staining, followed by catalase and oxidase tests. Isolates were characterized phenotypically, using the API 20 Strep kit (BioMerieux, France).…”

“…Amplification and sequencing of the 16S rRNA gene were performed by Fukushima et al [6] for three isolates (BR-LG1, BR-LG2, and BR-LG3) that had been randomly selected from the total number of strains isolated. 16S rRNA was amplified by PCR with the universal primers C70 (50-AGA GTT TGA TYMTGG C-30) and B37 (50-TAC GGY TAC CTT GTT ACG A-30) according to the method described in Fox et al [8].…”