Antibodies against Two Testudinid Herpesviruses in Pet Tortoises in Europe

SIMPLE SUMMARY: Herpesviruses are important pathogens in tortoises and cause latent infections. Serological testing is therefore an important tool for the detection of herpesvirus-infected tortoises. This retrospective study describes the detection of antibodies against two herpesviruses in pet tortoises in Europe. Of the 1728 samples tested, antibodies against one or both of the viruses used were detected in 122 (7.06%) of the tortoises. Detection rates differed depending on virus type, host species, and year of sampling. For individual viruses, detection rates also differed depending on season and country of origin. A better understanding of both the herpesviruses’ prevalences and the immune response to infection will help protect these animals in future. ABSTRACT: Herpesviruses are important pathogens of tortoises, and several serologically and genetically distinct virus types have been described in these animals. Virus neutralization testing is commonly used in Europe to determine previous infection with the two types most often found in pet European tortoises, testudinid herpesvirus (TeHV) 1 and 3. In this retrospective study, the results of serological testing for antibodies against each of these viruses in serum or plasma samples from 1728 tortoises were evaluated, and antibody detection rates were compared based on virus type, host species, year, season, and country of origin. Antibodies (titer 2 or higher) against at least one of the two viruses used were detected in a total of 122 (7.06%; 95% CI 5.95–8.37%) of the animals tested. The antibody detection rates differed significantly depending on the tortoise species (p < 0.0001) and the year of sampling (TeHV1 p = 0.0402; TeHV3 p = 0.0482) for both virus types. For TeHV1, antibody detection rates differed significantly (p = 0.0384) by season. The highest detection rate was in summer (5.59%; 95% CI 4.10–7.58%), and the lowest was in fall (1.25%; CI 0.53–2.87%). TeHV1 antibody detection rates did not differ significantly (p = 0.7805) by country, whereas TeHV3 antibody detection rates did (p = 0.0090). The highest detection rate, 12.94% (95% CI 7.38–21.70%), was found in samples from Italy. These results support previous hypotheses on the species’ susceptibility to TeHV1 and 3 and the use of serology as a diagnostic test for the detection of herpesvirus-infected tortoises.