Susceptibility of eastern water dragons Intellagama lesueurii lesueurii to Bohle iridovirus

Abstract

Ranaviruses infect and have been associated with mass mortality events in fish, amphibians and reptiles and are capable of interclass transmission. Eastern water dragons (EWDs), a semi-aquatic squamate, have an overlapping distribution with several species shown to be susceptible to Bohle iridovirus (BIV). However, this species has not been previously investigated, and no known mass mortalities have occurred in wild populations. Here we report the experimental infection of juvenile EWDs with BIV to investigate a water-dwelling lizards' susceptibility to a ranaviral strain present in northern Queensland, Australia. Lizards were exposed via oral inoculation, intramuscular injection, or cohabitation with orally infected lizards. All exposure methods were effective in establishing an infection as demonstrated by skin lesions and pathological changes in the internal organs. Necrosis, haemorrhage and inflammation were observed histologically in the pancreas, liver, spleen, kidney and submucosa of the gastrointestinal tract of BIV-exposed lizards. Variably sized basophilic intracytoplasmic inclusion bodies were observed in the liver of 6/14 BIV-exposed lizards. Virus was isolated from the liver and kidney of all BIV-infected lizards and confirmed with quantitative PCR (qPCR). The outcome of this study demonstrates that juvenile EWDs are susceptible to BIV, thereby adding Australian lizards to the broad host range of ranaviruses. Furthermore, this study provides additional evidence of BIV's ability to infect different classes of ecothermic vertebrates.

Dose-dependent morbidity of freshwater turtle hatchlings, Emydura macquarii krefftii, inoculated with Ranavirus isolate (Bohle iridovirus, Iridoviridae)

“…Similarly, i.m. inoculated eastern water dragons (EWDs) succumbed to infection more quickly than the hatchlings in this study [22]. EWDs developed clinical signs between 1-5 days and mortalities occurred 5-8 days post-inoculation with 10 5.33 TCID 50 ml −1 BIV, whereas the turtles developed clinical signs between 14-30 days and mortalities occurred 16-24 days post-inoculation with the same dose.…”

“…The BIV isolate used in this study was produced according to the methods of Maclaine et al [22]. Briefly, fathead minnow (FHM) cells were used to propagate the isolate at 25 °C.…”

Cutaneous Lesions in Freshwater Turtles (Emydura macquarii krefftii and Myuchelys latisternum) in a Rainforest Creek in North Queensland, Australia

“…Histological examination revealed that the condition was largely confined to the epidermis, while all other organs in the animals investigated appeared normal. Skin lesions associated with ranaviral infection have been reported in lizards and turtles, but in most cases internal organs were also infected (29)(30)(31)(32). While there was no detectable bias toward sex or species of turtles, the odds ratio indicates that the larger the turtle, the higher the risk of a lesion, and juveniles were rarely affected.…”

Peer Review #1 of "Ranaviruses and reptiles (v0.2)"

“…The hatchlings of both species of freshwater turtles were susceptible to infection via intra-coelomic exposure although oral inculcation was not attempted. Juvenile Australian eastern water dragons (Intellagama lesueurii lesueurii) developed ranaviral disease from all exposure routes tested (oral, intramuscular, and cohabitation) (Maclaine et al, 2018). Differences in susceptibility via different routes of exposure may reflect real differences in natural transmission routes between reptiles and other Classes.…”

“…Using total IgY levels as an internal control may minimise diagnostic errors resulting from seasonal variations in antibody levels. PCR based assays have been used conventionally and in quantitative real-time assays to detect reptilian ranaviruses in a number of sample types including blood, oral and cloacal swabs, and fresh and fixed tissues (Pallister et al, 2007;Allender et al, 2013a;Goodman et al, 2013, Butkus et al, 2017Leung et al, 2017;Maclaine et al, 2018). Molecular surveys of turtle populations for ranavirus have revealed that swabs and blood samples are not equally valid targets for ranavirus detection (Allender et al, 2013a).…”