The primary objective of this work was to determine the tissue-specific bioconcentration factors (BCFs) of the selected pharmaceuticals: norethindrone (NET), ibuprofen (IBU), verapamil (VER), clozapine (CLZ) and fenofibrate (FFB) in two freshwater fishes: fathead minnow and channel catfish. BCF tests on fathead followed the standard OECD 42-day test while a 14-day abridged test design was used in catfish exposures. Additional objectives included a) comparing the measured BCFs to the US EPA's BCFWIN model predicted values, b) comparing the BCF results from the standard and reduced tests, and c) prediction of chronic risk of the pharmaceuticals in fish using the human therapeutic plasma concentrations. Each test included uptake and depuration phases to measure tissue-specific kinetic BCFs. The results indicated that all the pharmaceuticals, except IBU, have the potential for accumulation in fish. Estimated BCFs for NET, VER and FFB may not be significant in view of the current regulatory trigger level (BCF ≥ 2000); however, CLZ's BCF in the liver had approached the criterion level. Significant differences were noticed in the tissue-specific uptake levels of the pharmaceuticals with the following general trend: (liver/kidney) > (gill/brain) > (heart/muscle) > plasma. IBU uptake was highest in the plasma. When compared to the measured BCFs, predicted values for NET, IBU, VER and FFB were slightly overestimated but did not differ largely. However, the measured BCF of CLZ in the liver was approximately two-orders of magnitude higher than the predicted level. The tissue-BCFs for the two species were not widely different indicating the potential usefulness of the reduced BCF test. Comparison of fish and human plasma levels indicated that NET, CLZ and VER have the potential to cause chronic effects in fish.

Thesis (Ph.D.)--Mississippi State University. Department of Agricultural and Biological Engineering. / Title from title screen. Includes bibliographical references.

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.

No description available.

Edwardsiella ictaluri causes enteric septicemia of catfish (ESC), a devastating disease in the channel catfish industry. Our research group has developed several E. ictaluri live attenuated vaccine (LAV) candidates (EiΔevpB, EiΔevpBΔfur, EiΔevpBΔhfq, EiΔevpBΔfurΔhfq), which were able to stimulate an immune response in vaccinated channel catfish and reduce ESC. However, innate, and adaptive immune responses in the lymphoid tissues of channel catfish to these LAVs are not known well. The overall goal of the project is to determine the role of adaptive and innate immune responses in catfish after vaccination with LAVs. Analysis of innate and adaptive immune-related gene expressions showed that the LAVs induced expression of adaptive immune-related genes in lymphoid tissues with less inflammation compared to wild type control. Also, the LAVs induced the expression of IgM in the sera of catfish.

Channel catfish virus disease (CCVD) is the principal viral disease in the United States catfish industry. The CCVD is caused by channel catfish virus (CCV), with mortality reaching up to 100% in fingerlings. CCV is assigned taxonomically to the family Alloherpesviridae, genus Ictalurivirus, species Ictalurid herpesvirus 1 (IcHV-1). To date, virulence, immunogenicity, and genome plasticity of the CCV field isolates have not been investigated. Three genotypes of CCV (IcHV-1A, IcHV-1B, and BCAHV) were identified using restriction fragment length polymorphism (RFLP) analysis. Virulence assessment of three representative isolates of RFLP groups suggests that IcHV-1B (pooled survival [mean ± SE]: 58.3% ± 2.6) showed significantly lower survival than IcHV-1A (68.6% ± 2.4). Re-exposure of the survivors with a representative of IcHV-1A and IcHV-1B isolates indicates a robust cross-protective effect (relative percent survival [RPS]: 80-100%). Antigenic determinants against anti-CCV monoclonal antibody Mab-95 were conserved among IcHV-1A, and IcHV-1B; however, BCAHV possesses antigenically distinct epitopes (Neutralization index [NI] = 0). Although BCAHV and CCV have nearly colinear genomes (except for the absence of ORF16A in CCV), they represent distinct species, given that nucleotide identity is 93.9%. Moreover, infectivity trials indicated that channel and hybrid catfish fingerlings might be refractive to LD50 (1.3×105 TCID50/L) dosage of BCAHV. However, previous exposure to BCAHV has protected the channel and hybrid catfish against the subsequent infection with the ATCC strain of CCV (RPS:100%). Next, two discriminatory duplex probe-based qPCR assays were designed and validated to diagnose latent IcHV-1A and IcHV-1B. Spatio-temporal survey of six Mississippi catfish hatcheries indicated that the prevalence of latent CCV genotypes varied between 25-100%. Lastly, twenty one reference quality genomes of CCV field isolates were assembled, and phylogenomic analyses supported the monophyly of the CCV field isolates with BCAHV as their closest relative. The phylogenomic analyses confirmed the two distinct genotypes (IcHV-1A and IcHV-1B) identified in RFLP analysis and further allowed the segregation of the IcHV-1A genotype into two subgroups, IcHV-1A1 and IcHV-1A2. Results from the current studies lay the foundation for future research and will help formulate efficient management strategies to reduce the economic impact of CCV in the catfish industry.