A Comparison of Fish Health Indices Applied to Freshwater Species of the Chesapeake Bay Watershed

Fish kills, increased disease prevalence, and endocrine disruption have been observed in multiple freshwater fish populations of the Chesapeake Bay watershed (CBW). Some of these health issues occur in conjunction with declining abundance. A combination of multiple stressors is believed to be weakening sensitive fish species in non-tidal regions of the CBW. Fish health indices such as Deformity, Erosion, Lesion, and Tumor counts (DELTs), and the Health Assessment Index (HAI) are simple tools designed to evaluate the general health of fish populations. Both indices could be widely applied in the watershed because they require limited training and equipment. However, their utility in the CBW needs to be demonstrated. Fish health concerns in the CBW often occur in areas dominated by forested and agricultural land. The research in this thesis evaluates the influences of agricultural land-use, season, seasonal stream discharge, species, age, and sex on DELTs and the HAI. Two studies are included. The first occurred in the Shenandoah Valley of Virginia and West Virginia and applies the DELT index to fish aggregations and the HAI to white sucker and fantail dater in wadable streams. These streams were spread over a gradient of catchment pastureland. The second looked at DELTs and the HAI applied to smallmouth bass at 5 sites, 2 in the Potomac River watershed and 3 in the Susquehanna River watershed, sampled from 2013 to 2020 in the spring and fall. These sites varied in catchment agricultural and forested land with small areas of development. The utility of the two indices in agricultural regions of the CBW was not demonstrated. Both DELTs and HAI scores were correlated with the age and sex of fish sampled, and not with any of the included environmental variables. Future research directions and other concerns surrounding the use of DELTs, and the HAI are discussed

Human Beta Defensin 2 Ameliorated Alcohol-Associated Liver Disease in Mice

Alcohol-associated liver disease (ALD) is a prevalent liver disorder and significant global healthcare burden with limited effective therapeutic options. The gut-liver axis is a critical factor contributing to susceptibility to liver injury due to alcohol consumption. In the current study, we tested whether human beta defensin-2 (hBD-2), a small anti-microbial peptide, attenuates experimental chronic ALD. Male C57Bl/6J mice were fed an ethanol (EtOH)-containing diet for 6 weeks with daily administration of hBD-2 (1.2 mg/kg) by oral gavage during the final week. Two independent cohorts of mice with distinct baseline gut microbiota were used. Oral hBD-2 administration attenuated liver injury in both cohorts as determined by decreased plasma ALT activity. Notably, the degree of hBD-2-mediated reduction of EtOH-associated liver steatosis, hepatocellular death, and inflammation was different between cohorts, suggesting microbiota-specific mechanisms underlying the beneficial effects of hBD-2. Indeed, we observed differential mechanisms of hBD-2 between cohorts, which included an induction of hepatic and small intestinal IL-17A and IL-22, as well as an increase in T regulatory cell abundance in the gut and mesenteric lymph nodes. Lastly, hBD-2 modulated the gut microbiota composition in EtOH-fed mice in both cohorts, with significant decreases in multiple genera including Barnesiella, Parabacteroides, Akkermansia, and Alistipes, as well as altered abundance of several bacteria within the family Ruminococcaceae. Collectively, our results demonstrated a protective effect of hBD-2 in experimental ALD associated with immunomodulation and microbiota alteration. These data suggest that while the beneficial effects of hBD-2 on liver injury are uniform, the specific mechanisms of action are associated with baseline microbiota