Identification and Characterization of Scutavirus testudinidalpha3 Infection in Captive Elongated Tortoises (Indotestudo elongata).

Scutavirus testudinidalpha3, formerly Testudinid alphaherpesvirus 3 or testudinid herpesvirus (TeHV)-3, is a highly contagious herpesvirus that has been reported in multiple testudinid species, causing acute stomatitis-rhinitis complex in affected animals or establishing latent infections in surviving individuals. This study investigated an outbreak of S. testudinidalpha3 infection in 17 elongated tortoises (Indotestudo elongata) housed exclusively in an outdoor zoo enclosure in Taiwan in March, 2022. The affected tortoises exhibited nasal and ocular discharge and diphtheroid plaques on the oral mucosa. Despite prompt isolation and supportive treatment, 14 individuals succumbed. Necropsy and histopathologic examination revealed severe necrosis with inflammation, characterized by eosinophilic intranuclear inclusion bodies and occasional syncytial cells in multiple organs. Conventional polymerase chain reaction (PCR) and in situ hybridization (ISH) confirmed S. testudinidalpha3 infection. DNA polymerase (DNApol) gene sequences were identical among all individuals and shared 97.86% nucleotide similarity with the German 4295/7R strain. Furthermore, the full-length sequence of glycoprotein B (gB), a potential virulence factor in herpesviruses, showed 99.9% identity with the Switzerland CH6883/03 strain, classifying this isolate as belonging to the genogroup B, known for its high pathogenicity. This report documents the first confirmed case of S. testudinidalpha3 infection in elongated tortoises.