Theses and Dissertations

ORCID

0000-0002-8733-6433

Advisor

Abdelhamed, Hossam

Committee Member

Petrie-Hanson, Lora

Committee Member

Griffin, Matt

Committee Member

Yamamoto, Fernando

Date of Degree

8-12-2026

Original embargo terms

Visible MSU Only 2 Years

Document Type

Dissertation - Campus Access Only

Major

Veterinary & Biomedical Science (Infectious Disease)

Degree Name

Doctor of Philosophy (Ph.D.)

College

College of Veterinary Medicine

Department

Department of Comparative Biomedical Sciences

Abstract

Aquaculture is the fastest-growing sector of animal food production, with catfish production being the largest segment of the aquaculture industry in the United States. Phytochemicals, such as trans-cinnamaldehyde (TC), have the potential to reduce mortalities associated with Edwardsiella ictaluri, a devastating bacterial pathogen that causes enteric septicemia of catfish (ESC). The objective of this study was to enhance the antibacterial efficacy of TC while improving its palatability and optimizing its dietary feeding regimen. Our results indicated that the optimal TC feeding regimen is 15 mL/kg feed. This regimen significantly improved survival to 67.5% compared with only 15% survival in the control group. Using the ultrasonication/freeze-drying method for encapsulating TC with β-CD provided adequate protection (50% survival at a 2 g/kg dose). Additionally, Mβ-CD encapsulation resulted in a substantial increase in catfish survival (60% at the 4 g/kg dose). Chitosan nano-encapsulated TC resulted in survival rates of 48.6% at 1.39 g/kg feed, compared with 25% for the regular diet and 74.5% in the unencapsulated TC. Catfish fed TC, TC+PA, and florfenicol-supplemented diets showed significant downregulation of key pro-inflammatory cytokine genes, suggesting anti-inflammatory effects. By Days 7 and 14, a significant upregulation of T- and B-cell-related genes was observed, suggesting that TC supplemental dietary intake can improve catfish immune status by engaging innate and adaptive immune responses and promoting memory cell production in immunocompetent tissues. Microbiome changes over time were assessed using alpha- and beta-diversity. Florfenicol-treated groups consistently diverged, suggesting a distinct abundance-driven community restructuring, whereas TC15+PA5 overlapped more closely with TC15. The relative abundance analyses showed that TC15 and TC+PA maintained more balanced distributions, with higher proportions of Fusobacteria, Firmicutes, Bacteroidetes, Cetobacterium, and Romboutsia, while florfenicol increased the relative abundance of Proteobacteria and reduced Fusobacteria over time. On day 14, florfenicol-treated fish remained dominated by Aeromonas, suggesting a more disrupted microbial profile compared with TC-based treatments. In conclusion, this dissertation establishes TC as a powerful, practical, and microbiome-preserving antimicrobial alternative for controlling ESC in channel catfish. The integration of optimized dosing, dietary synergists, encapsulation strategies, and microbiome analysis provides a robust scientific foundation for transitioning toward antibiotic-sparing disease management in aquaculture.

Sponsorship (Optional)

USDA-NIFA

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