Pathogenesis of Bohle Iridovirus (Genus Ranavirus) in Experimentally Infected Juvenile Eastern Water Dragons ( Intellagama lesueurii lesueurii).

Abstract

Juvenile eastern water dragons ( Intellagama lesueurii lesueurii) are highly susceptible to infection with Bohle iridovirus (BIV), a species of ranavirus first isolated from ornate burrowing frogs in Townsville, Australia. To investigate the progression of BIV infection in eastern water dragons, 11 captive-bred juveniles were orally inoculated with a dose of 104.33 TCID50 and euthanized at 3, 6, 8, 10, 12, and 14 days postinfection (dpi). Viral DNA was detected via polymerase chain reaction (PCR) in the liver, kidney, and cloacal swabs at 3 dpi. Mild lymphocytic infiltration was observed in the submucosa and mucosa of the tongue and liver at 3 dpi. Immunohistochemistry (IHC) first identified viral antigen in foci of splenic necrosis and in hepatocytes with intracytoplasmic inclusion or rare single-cell necrosis at 6 dpi. By 14 dpi, positive IHC labeling was found in association with lesions in multiple tissues. Selected tissues from an individual euthanized at 14 dpi were probed using in situ hybridization (ISH). The ISH labeling matched the location and pattern detected by IHC. The progression of BIV infection in eastern water dragons, based on lesion severity and virus detection, appears to start in the spleen, followed by the liver, then other organs such as the kidney, pancreas, oral mucosa, and skin. The early detection of ranaviral DNA in cloacal swabs and liver and kidney tissue samples suggests these to be a reliable source of diagnostic samples in the early stage of disease before the appearance of clinical signs, as well as throughout the infection.