Genetic selection for the tilapia (Oreochromis niloticus) production resistant against Streptococcus agalactiae (serotype Ib and genetic variant non-typeable)

• Grant number: 19/23029-0
• Support Opportunities: Research Grants - Innovative Research in Small Business - PIPE
• Start date: February 01, 2021
• End date: October 31, 2021
• Field of knowledge: Agronomical Sciences - Fishery Resources and Fishery Engineering - Aquaculture
• Principal Investigator: Rubens Ricardo de Oliveira Neto
• Grantee: Rubens Ricardo de Oliveira Neto
• Company: Genosel Desenvolvimento Experimental em Ciências Físicas e Naturais
• CNAE: Aqüicultura em água doce
• City: Jaboticabal
• Pesquisadores principais: Diogo Teruo Hashimoto
• Associated researchers: Fabiana Pilarski

Abstract

Nile tilapia (Oreochromis niloticus) is one of the main species of continental aquaculture production, being the most cultivated in Brazilian aquaculture. Streptococcosis shorts, associated with Streptococcus agalactiae infection, have been reported in commercial fish farms worldwide and often cause high mortality rates in Brazil. S. agalactiae is a gram-positive bacterium that has different serotypes (specificity in its capsular polysaccharide), and different genetic variants, which may be restricted according to geographic region. For this reason, vaccines are not fully effective, whereas Genetic breeding can be a viable and sustainable alternative to breed animals resistant to this bacterium. The aim of this study is to obtain S. agalactiae-resistant tilapia by means of a challenge test using a serotype Ib strain (non-typeable genetic variant), which is circulating in fish farms in south-central Brazil and has caused economic losses. to tilapia producers. In total, the experimental population will be composed of families of complete siblings, resulting from animals from the genetic breeding nucleus of the Unesp Aquaculture Center, in Jaboticabal, SP. Infection will be induced via intraperitoneal inoculation with a dose of 0.15 ml of bacteria, from the concentration previously determined in LD50. The experiment will be conducted for a period of 21 days to evaluate the resistance characteristics such as survival rate and time of death (in days). The expected result is to obtain reliable data to select resistant Tilapia against Streptococcus agalactiae (serotype Ib, non-typeable genetic variant), which can be routinely traded in fish farms in the Center-South of Brazil, reducing disease outbreaks and, consequently, the disease. indiscriminate use of antibiotics and high costs with vaccination. Finally, we hope to foster the production of genetically resistant tilapia, in a sustainable and safe manner, adding value and quality to fish for the final consumer. (AU)