Location: Aquatic Animal Health Research
Project Number: 6010-32000-027-009-C
Project Type: Cooperative Research and Development Agreement
Start Date: Dec 1, 2015
End Date: Nov 30, 2020
Objective:
The objective is to determine the genetic susceptibility of Nile tilapia families originating from the SPRING GENETICS Nile tilapia breeding program, with nucleus operations in Homestead, Florida, U.S., to Streptococcus iniae, Streptococcus agalactiae, and/or other pathogens of tilapia (such as: Francisella noatunensis orientalis, Flavobacterium columnare, Aeromonas spp., tilapia lake virus (TiLV)). The data generated from these studies will be used to incorporate disease resistance into the selective breeding program of SPRING GENETICS.
Approach:
Each year, ARS will perform 1 or 2 (n = 2) bacterial and/or viral challenges using Nile tilapia originating from the SPRING GENETICS breeding program. The approach for each bacterial challenge will be similar and will be conducted as outlined below. For each bacterial challenge, SPRING GENETICS will transport Nile tilapia originating from different families (up to 160 families), to ARS. Upon delivery, fish will be acclimated for 7-10 days prior to bacterial challenge and fed daily (2-3% body weight) with Aquamax Grower feed (PMI Nutrition International, Inc., Brentwood, MO, USA). The PIT tag number and date of death will be recorded using an ISO handheld reader (ARE H5; AEG ID, Ulm, Germany) for mortalities that occur during the acclimation period. Following acclimation, fish will be challenged with Streptococcus (S.) iniae, S. agalactiae, and/or other pathogens (such as: Francisella noatunensis orientalis, Flavobacterium columnare, Aeromonas spp., tilapia lake virus (TiLV)) tilapia by either intraperitoneal injection, intramuscular, immersion, and/or cohabitation disease models. Prior to challenge, the PIT tag number of each fish will be recorded. Following challenge, dead fish will be removed twice daily for 21-28 day or until no mortalities are recorded for 3-5 day. The PIT tag numbers and date of death of each fish will be recorded. Following challenge, dead fish will be removed twice daily for 21-28 day or until no mortalities are recorded for 3-5 day. The PIT tag numbers and date of death of each fish will be recorded. PIT tags will be removed from each fish and returned to SPRING GENETICS. Re-isolation of S. iniae, S. agalactiae, or other pathogens used in the challenges will be attempted daily from a minimum of 20% of the dead fish by inoculating brain tissue onto sheep blood agar or appropriate medium. Upon termination of the challenge, all surviving fish will be euthanized, examined for clinical signs of disease, and PIT tag numbers will be recorded and removed from fish. ARS will provide Akvaforsk Genetic Centre (AFGC) with all data generated from the bacterial challenges. AFGC will analyze the data using univariate animal, linear and sire-dam threshold, and/or other relevant statisitical models to obtain estimates of variance components for estimation of heritability and family breeding values for resistance to these tilapia pathogens. The data generated from these studies will be used to incorporate disease resistance into the selective breeding program of SPRING GENETICS and AFGC.
