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ARS Home » Southeast Area » Auburn, Alabama » Aquatic Animal Health Research » Research » Publications at this Location » Publication #397532
Research Project: Integrated Research to Improve Aquatic Animal Health in Warmwater Aquaculture

Location: Aquatic Animal Health Research

Title: Streptococcus iniae challenge induces minimal acute histopathological changes in Nile tilapia (Oreochromis niloticus) selectively bred for disease resistance

Author
item Beck, Benjamin
item Lafrentz, Benjamin
item Shoemaker, Craig
item LOZANO, CARLOS - Benchmark Genetics
item VELA-AVITUA, SERGIO - Benchmark Genetics
item F. OSPINA-ARANGO, JOSE - Spring Genetics
item YAZDI, HOSSEIN - Benchmark Genetics
item RYE, MORTON - Benchmark Genetics
item FOGELSON, SUSAN - Fishhead Labs Llc
item Deshotel, Michael
item PEATMAN, ERIC - Auburn University

Submitted to: European Association of Fish Pathologists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2024
Publication Date: 9/6/2024
Citation: Beck, B.H., Lafrentz, B.R., Shoemaker, C.A., Lozano, C.A., Vela-Avitua, S., F. Ospina-Arango, J., Yazdi, H., Rye, M., Fogelson, S.B., Deshotel, M.B., Peatman, E. 2024. Streptococcus iniae challenge induces minimal acute histopathological changes in Nile tilapia (Oreochromis niloticus) selectively bred for disease resistance. European Association of Fish Pathologists. 44:2. https://doi.org/10.48045/001c.122603.2024.
DOI: https://doi.org/10.48045/001c.122603

Interpretive Summary: Streptococcus iniae is a causative agent of streptococcal disease that negatively impacts tilapia production worldwide. Previously, our collaborative research team demonstrated substantial genetic variation for resistance to S. iniae and confirmed the ability to improve resistance through selective breeding. Although positive gains in resistance have been achieved, the underlying mechanisms involved in the observed resistance are unknown. To address this knowledge gap, tilapia produced via marker assisted selection to determine resistant and susceptible parents were challenged with S. iniae to confirm resistance and susceptibility. Organ samples were collected from challenged individuals for histology prior to and 24 h post-challenge. The resistance was confirmed as demonstrated by 100% survival in the resistant tilapia and only 10% survival in the susceptible tilapia following S. iniae challenge. Lesions observed in the anterior kidney, spleen and brain of susceptible tilapia were consistent with classic S. iniae infection including inflammation in the brain, spleen, and kidney. The severity of these lesions was greatly reduced in the resistant tilapia and no S. iniae were observed in the tissues. The increased understanding of the histopathological changes observed provides a foundation for further research to determine the mechanisms involved in the resistance observed.

Technical Abstract: Streptococcus iniae is a causative agent of streptococcal disease that negatively impacts tilapia (Oreochromis spp.) production worldwide. Previously, our collaborative research team demonstrated substantial genetic variation for resistance to S. iniae and confirmed the ability to improve resistance through selective breeding. Although positive gains in resistance have been achieved, the underlying mechanism(s) involved in the observed resistance are unknown. To address this knowledge gap, the objective of this work was to describe differences in mortality and pathology between S. iniae resistant and susceptible strains of Nile tilapia. Marker assisted selection was used to produce tilapia from resistant and susceptible parents. The tilapia were challenged with S. iniae and organ samples were collected from challenged individuals for histology prior to and 24 h post-challenge. The resistance phenotype was confirmed as demonstrated by 100% survival in the resistant tilapia and only 10% survival in the susceptible tilapia following S. iniae challenge. Lesions observed in the anterior kidney, spleen, and brain of susceptible tilapia were consistent with classic S. iniae infection including histiocytic meningitis, splenitis, nephritis, and the presence of gram-positive cocci. The severity of these lesions was greatly reduced in the resistant tilapia and no S. iniae were observed in the tissues. Changes described through histological assessment of S. iniae challenged tilapia provide a foundation for subsequent research to elucidate the mechanisms governing the improved survival and reduced lesion formation in the resistant tilapia.