Pathogenicity of Frog Virus 3-like Virus in Red-eared Slider Turtles (Trachemys scripta elegans) at Two Environmental Temperatures

SummaryRanaviral disease has affected several species of reptiles, but disease progression and mortality in relation to environmental temperature has yet to be determined. In this study, two separate trials challenged adult female red-eared slider turtles (Trachemys scripta elegans) with a ranavirus (frog virus 3-like virus; FV3) isolate at environmental temperatures of 22°C (n = 4) and 28°C (n = 4). The mortality rates in the turtles in the 22°C and 28°C trials were 100% and 50%, respectively. Median survival time for turtles exposed to FV3 at 22°C was 24 days, while it was 30 days in the group kept at 28°C. Consistent microscopical lesions were observed only in the group inoculated at 22°C and included fibrinoid necrosis of vessels in the spleen, vascular and sinusoidal thrombi in the liver, necrotizing myositis and a mild heterophilic interstitial pneumonia. Quantitative polymerase chain reaction, targeting a conserved portion of the major capsid protein, was able to detect virus copies in whole blood, oral and cloacal swabs, tongue, skeletal muscle, lung, heart, liver, spleen, ovary and kidney. Viral copy number in ante-mortem clinical samples was non-significantly highest in whole blood, while kidney had the highest viral copy number in post-mortem samples. All samples had higher virus copy number in turtles exposed to FV3 at 22°C compared with 28°C. This study determined that environmental temperature affects the survival and disease progression in ranavirus-infected red-eared slider turtles, which will aid in managing animals in a clinical or free-ranging setting.