Investigations on the prevalence of tortoise picorna-virus in captive tortoises in Germany

Objective: Tortoise picornavirus (ToPV) has been speculated to play an important role in the frequently seen disease pattern of juvenile shell softening. This study aimed to determine ToPV prevalence among German tortoise collections. Material and methods: A total of 334 animals selected from 27 different collections were included. Seven species of four genera of the family Testudinidae ( Testudo graeca, T. hermanni, T. marginata, T. horsfieldii, Centrochelys sulcata, Stigmochelys pardalis, Chelonoidis carbonarius ) were sampled. The tortoises were clinically investigated and none of the adults showed any signs of shell softening. Seven hatchlings of a ToPV-positive T. graeca breeding pair showed retarded growth and a progressive shell weakness that resulted in death. Each animal was sampled by conjunctival, pharyngeal and cloacal swabs (990 swabs in total) and blood sampling (293 in total). All three swabs of one animal were pooled and tested by reverse transcriptase polymerase chain reaction (RT-PCR) for tortoise picornavirus RNA. Blood samples were investigated by virus neutralisation test (VNT) for specific anti ToPV antibodies. All titres equal to or higher than log2 = 2 were considered positive. Results: In total, 35 adult and 11 juvenile animals were tested positive for ToPV RNA. The serological investigation did detect specific antibodies against ToPV in 44 adult tortoises and one juvenile. In total, 76 animals were tested positive in either one of the investigations, 16 animals in both. The highest number of ToPV-positive animals was found for T. graeca , with a prevalence of 32 %. No specimens of C. carbonarius, C. sulcata , or S. pardalis were tested positive. Conclusion and clinical relevance: The results propose a predisposition in T. graeca , as well as a high prevalence of ToPV in T. graeca , whereas other species showed only single or no positive animals, but may function as virus carriers.