Theses and Dissertations


Issuing Body

Mississippi State University


Hanson, Larry A.

Committee Member

Petrie-Hanson, Lora

Committee Member

Peterman, Ann E. (Beth)

Committee Member

Ross, Matthew K.

Date of Degree


Document Type

Graduate Thesis - Campus Access Only


Veterinary Medicine Science

Degree Name

Master of Science (M.S.)


College of Veterinary Medicine


Veterinary Medical Science Program


Microcystin-LR is a hepatotoxin produced by cyanobacteria. Aeromonas hydrophila and Edwardsiella piscicida infections are leading causes of losses in market-sized channel catfish (Ictalurus punctatus). These older fish should have natural immunity in place and a predisposing factor is likely a prerequisite for these disease outbreaks. While microcystin-LR rarely causes mortality in warm-water aquaculture, we believe it may be a predisposing factor that leads to bacterial disease outbreaks during the summer months due to its ability to damage the liver. Our study investigated microcystin-LR’s effects on channel catfish susceptibility to these pathogens. We found that a sublethal dose of microcystin-LR induced substantial damage to multiple immune organs. In our challenges with both the toxin and bacteria, we saw a significant increase in mortality of fish. Our findings suggest that microcystin-LR increases channel catfish susceptibility to Aeromonas hydrophila and Edwardsiella piscicida infections.