Epidemiology of Sulawesi Tortoise Adenovirus in Free-living Blanding's Turtles (Emydoidea blandingii), Painted Turtles (Chrysemys picta), and Red-eared Sliders (Trachemys scripta elegans) in Illinois, USA.

Sulawesi tortoise adenovirus (STADV) has been implicated in a mortality event involving three endangered species of tortoises and detected in free-living painted turtles (Chrysemys picta); however, the epidemiology of this virus in North American turtles remains unclear. The specific objectives of this study were to 1) estimate the prevalence of STADV in free-living Blanding's turtles (Emydoidea blandingii), painted turtles, and red-eared sliders (RES; Trachemys scripta elegans) in Illinois, US, using quantitative PCR (qPCR) and 2) determine if qPCR prevalence is associated with location, sex, age class, blood parameters, or clinical signs across these three species. Oral-cloacal swabs from 581 Blanding's turtles, 137 painted turtles, and 82 RES sampled across three counties from 2017 to 2022 were evaluated via qPCR. The prevalence of STADV was 2.4% for Blanding's turtles, 14.9% for painted turtles, and 45% for RES. Blanding's turtle subadults (P=0.022) and painted turtle adults (P<0.0001) were more likely to test positive than other age classes within the same species, while no age class association was found in RES (P=0.5). Clinical signs associated with STADV detection included quiet, alert, responsive mentation (P=0.002), pink mucous membranes (P<0.001), carapacial abnormalities (P=0.036), and plastron abnormalities (P=0.003). In a multivariable model, significant predictors for STADV detection included species, with painted turtles (P<0.0001) and RES (P=0.001) more likely to test positive than Blanding's turtles, and year, with turtles sampled in 2021 less likely to test positive than those sampled in 2017 (P=0.005). Detection of STADV was not significantly associated with location, month, sex, hematologic findings, serum biochemical findings, or protein electrophoretic profiles. Widespread molecular detection of STADV in these three species suggests a possible origin for the virus in the outbreak described in 2009, underscoring the importance of epidemiology studies to aid in the management of free-living and managed chelonians.