29th Annual Meeting and Symposium of the
Desert Tortoise Council, February 20-23, 2004
Abstracts

Iridovirus Infections of Turtles and Tortoises

April J. Johnson and Elliott R. Jacobson
College of Veterinary Medicine, University of Florida, Gainesville, Florida 32608

Iridoviruses are DNA viruses capable of infecting invertebrates and poikilothermic vertebrates. Five genera are recognized, of which the genus Ranavirus has been shown to infect fish, amphibians and reptiles (Mao et al, 1997). Several accounts of iridovirus infection have been documented in chelonians (Heldstab and Bestetti, 1982, Marschang et al, 1999). In the U.S., only three cases have been reported; a Russian tortoise (Testudo horsfieldii), and a box turtle (Terrapene carolina) in which no pathology was mentioned (Mao et al, 1997) and a wild gopher tortoise (Gopherus polyphemus) that had signs of respiratory disease (Westhouse et al, 1996). Between July and October 2003, a captive Burmese star tortoise (Geochelone platynota) from Georgia, a wild gopher tortoise (Gopherus polyphemus) from Florida and six Eastern box turtles (Terrapene carolina carolina) from Pennsylvania were found to be infected with iridovirus. Clinical signs were similar to those seen with herpesvirus infection and included conjunctivitis, rhinitis, and stomatitis. On histopathology, necrosis of multiple tissues was seen and basophilic intracytoplasmic inclusion bodies were observed in epithelial cells of the oral mucosa and hematopoietic cells in several organs. From the tortoises and box turtles, a virus compatible with iridovirus was isolated in Terrapene heart cells and using PCR, a segment of the gene encoding the major capsid protein was amplified and sequenced. BLAST analysis indicated that the DNA segment was most closely related to that of Frog Virus 3. An iridovirus with the same DNA sequence as the isolate from the Burmese star tortoise was isolated from an ill leopard frog in the star tortoise's enclosure suggesting amphibians may serve as a reservoir host for chelonians.

References

Heldstab, A., and G. Bestetti. 1982. Spontaneous viral hepatitis in a spur-tailed Mediterranean land tortoise (Testudo hermanni). Journal Zoo Animal Medicine 13:113-120.

Mao, J., R.P. Hedrick, and V.G. Chinchar. 1997. Molecular characterization, sequence analysis and taxonomic position of newly isolated fish iridoviruses. Virology. 229: 212-220.

Mao, J., D.E. Green, G. Fellers, and V.G. Chinchar. 1999. Molecular characterization of iridoviruses isolated from sympatric amphibians and fish. Virus Research. 63:45-52.

Marschang, R.E., P. Becher, H. Posthaus, P. Wild, H-J. Thiel, U. Müller-Doblies, E.F. Kaleta, and L.N. Bacciarini. 1999. Isolation and characterization of an iridovirus from Hermann's tortoises (Testudo hermanni). Archives of Virology. 144:1909-1922.

Westhouse, R.A., E.R. Jacobson, R.K. Harris, K.R. Winter, and B.L. Homer. 1996. Respiratory and pharyngo-esophageal iridovirus infection in a gopher tortoise (Gopherus polyphemus). Journal of Wildlife Diseases. 32: 682-686.