Aquaculture America 2024

February 18 - 21, 2024

San Antonio, Texas

CONTROLLED LABORATORY CHALLENGE DEMONSTRATES MODERATE ADDITIVE GENETIC VARIATION IN RESISTANCE TO TILAPIA LAKE VIRUS IN NILE TILAPIA

Benjamin R. LaFrentz* , Amber E . Johnston, Carlos A. Lozano,  Jose Fernando Ospina-Arango,  Craig A. Shoemaker, Sergio Vela-Avitúa , Morten Rye, Benjamin H. Beck

 

USDA-ARS

Aquatic Animal Health Research Unit

990 Wire Road

Auburn, AL , 36832

benjamin.lafrentz@usda.gov



Tilapia lake virus (TiLV)  is a lethal virus impacting farmed tilapia ( Oreochromis  spp.). The virus  was identified  in 2014 and  its emergence has resulted in substantial economic losses to the global tilapia industry. Given the lack of treatment options currently available, selective breeding for increased disease resistance may be a viable option for reducing the impact of this pathogen . Therefore, this study was initiated to phenotype Nile tilapia (O. niloticus ) families for resistance to TiLV  and determine  its additive genetic variation and heritability.  Fish from the eleventh generation  of the Spring Genetics Nile tilapia breeding program with nucleus operations in Homestead, Florida, US, were used for this study .  A total of 142 full-sib families (mean weight, 142.3 g)  were  included in the challenge with  on average  17 fish per family (range,  4  to 20) . All fish were  challenged  at the USDA-ARS AAHRU with TiLV via intraperitoneal injection with a viral dose corresponding to 2.25 × 104 TCID 50 fish-1 and placed into a single 5,550 L tank.  Mortality data  on each individual fish  was collected  for 21 days post challenge  and a univariate animal linear model was used for quantitative genetic analyses. The a ccumulated  mortality at the end of  the experiment was 74.5% .  The results revealed high variation in  the mean survival of the families  challenged with TiLV (range, 0% to 95 %). The  additive genetic effect for survival to TiLV was significantly different  from  zero (P < 0.001; log-likelihood ratio) and the  estimated  heritability  was h2 = 0.29 ± 0.1 . The results demonstrated moderate additive genetic variation in resistance to TiLV and suggest promise in genetic improvement of tilapia for resistance  to this virus by selective breeding. Genomic analyses are pending to evaluate the potential for genomic or marker assisted selection. In the next generation, families will be produced by assortative mating (high and low estimated breeding values) and challenged to confirm the heritability of resistance to TiLV. The end goal is the production of a high performing strain of tilapia with disease resistance for the global tilapia industry.