A longitudinal analysis of pathogen shedding patterns in confiscated eastern box turtles

Abstract

Eastern box turtles (Terrapene carolina carolina) have experienced population declines due to the illegal wildlife trade and its association with the spread of infectious diseases, yet the dynamics of infections are not thoroughly described. In the fall of 2022, 17 confiscated eastern box turtles arrived at the University of Illinois after being intercepted from the illegal wildlife trade with an initial 41.2% prevalence of frog virus 3 (FV3). We housed turtles individually and tested them for FV3, Terrapene herpesvirus 1 (TerHV1), box turtle Mycoplasma sp. (BTMyco), and Terrapene adenovirus (TerAdv) via quantitative polymerase chain reaction (qPCR) on combined oral and cloacal swabs monthly for 13 months. We used occupancy models to determine unbiased pathogen prevalence and detection probabilities for infected turtles. No turtles tested positive for FV3 after initial testing. Observed pathogen prevalence values were within 10% of unbiased prevalence estimates; however, the probability of detecting pathogens in an infected turtle during a given month was generally low (TerHV1 = 32.7%, TerAdv = 21.2%, and BTMyco = 49.9%). Turtles were intermittently co-detected with both BTMyco and TerHV1 (n = 7), BTMyco and TerAdv (n = 10), and TerHV1 and TerAdv (n = 6). In co-detections, the presence of TerHV1 and BTMyco decreased the detection probabilities of other pathogens. Of the 2 turtles that died, gross and histologic findings included nephritis in both turtles, one of which had severe inflammation, and the other turtle had a large coelomic hematoma. This study provides evidence-based sampling strategies to maximize the detection of individuals infected with common box turtle pathogens. The best detection rate for 2 swabs includes monthly sampling for BTMyco, TerHV1, and TerAdv, but if turtles are housed for longer, 2 swabs every third month should be used for optimal detection. These findings have implications for the design and interpretation of research studies and clinical management of box turtles in managed care and can inform placement and release decisions during confiscation events.