Long-term monitoring of four Scutavirus testudinidalpha3-infected Mediterranean tortoises (Testudo spp.) from a 2013 outbreak: a case study

Scutavirus testudinidalpha3 (formerly known as Testudinid alphaherpesvirus 3) is a virus causing severe and ultimately fatal diseases in Mediterranean tortoises. The virus can alternate between a lytic phase, involving viral replication, and a latent stage. It is considered a threat for all the Testudinidae, including endangered species. Longterm outcomes of surviving animals post-primary infection remain unstudied. The aim of this work was to conduct an 8-year long-term monitoring study of a group of Scutavirus testudinidalpha3-infected Mediterranean tortoises, including two Testudo hermanni hermanni and two T. graeca ibera, that survived a high mortality-associated outbreak in 2013. Serological (ELISA) and molecular test (PCR from oral swab) were employed for the long-term monitoring of the infection on the four Testudo spp. Scutavirus testudinidalpha3 DNA and anti-Scutavirus testudinalpha3 antibodies were detected in three animals after 7-and 8-years post-outbreak, respectively. The fourth individual tested negative both by PCR and serology after an initial transient positivity recorded during the outbreak. Despite the limited sample size, the combination of clinical diagnosis and laboratory results assessed during investigation underscore the complexity and unpredictability of Scutavirus testudinidalpha3 infection and its long-term outcomes. These findings should be considered in the management and exchange of tortoises, especially those from different origins.