Virus isolation and vaccination of Mediterranean tortoises against a chelonid herpesvirus in a chronically infected population in Italy

A chelonid herpesvirus was isolated from a group of tortoises in Italy with a history of increased mortality and upper digestive and respiratory tract disease. The isolated virus was inactivated with formalin and used to prepare a nonadjuvanted vaccine and a vaccine adjuvanted with aluminum hydroxide. 57 tortoises, 26 Testudo hermanni, 25 T. graeca, and 6 T. marginata, were included in the study. The animals were vaccinated 3 times at 45 day intervals. Blood was collected from the animals 14 days prior to the first vaccination, and on day 0, 25, 45, 90, 113 and 369 after the first vaccination. Plasma antibody titers to the homologous chelonid herpesvirus were determined using a virus neutralization test (VNT). No significant rise in antibody titer was noted in the vaccinated animals. Antibody titers measured dropped below the cutoff-level sporadically in all positive animals. Repeat serological testing may therefore be necessary in order to detect seropositive animals.