David Steffen’s scientific contributions

Aural abscesses are a common health problem in free-ranging eastern box turtles (Terrapene carolina carolina), and they have been associated with high body burdens of organochlorine (OC) compounds, which are known disruptors of vitamin A. The objective of this study was to determine if the presence of pathologic lesions in box turtles were correlated with increased and decreased levels of hepatic OC compounds and vitamin A, respectively. A graded scale for the pathologic changes observed in tissue samples collected from abscessed and nonabscessed box turtles over a 2-yr period (2003-04) was developed, and the levels of OC compounds and vitamin A in livers collected from the same turtles were determined through chemical analysis. Sixty-eight turtles (40 with aural abscesses and 28 without) were included in the study. Relationships between variables were analyzed using Spearman's Rank Correlation Test, where P</=0.05 was considered significant. Twenty-seven different OC compounds were identified. Mean+/-standard deviation (SD) total OC compound level for all turtles was 0.35+/-0.83 ppm (range 0-5.81 ppm), and mean+/-SD vitamin A level was 72.8+/-98.6 ppm (range 0-535.7 ppm). There was no correlation between pathologic score and total hepatic OC compound concentration (r = -0.18, P = 0.16). However, pathologic score was positively correlated with o,p'-DDT (r = 0.25, P = 0.05). Vitamin A was positively correlated with pathologic score (r = 0.32, P = 0.01), which was contrary to the expected result. There was no linear correlation between vitamin A and total hepatic OC compound concentration (r = -0.04, P = 0.75). However, a nonlinear regression provided a significant fit (r(2) = 0.12, P = 0.02), indicating an initial increase in vitamin A as the OC compound burden increased, followed by a decline as OC compound levels increased further. The hepatic OC compound residue concentrations in these box turtles were lower compared to levels found in freshwater aquatic turtles but similar to levels in other terrestrial reptile species. This study provides mixed results in support of a role of OC compounds, presumably of environmental origin, in the etiology of aural abscesses in free-ranging box turtles.