Ranavirus and the fungus Batrachochytrium dendrobatidis (Bd) are emerging infectious pathogens that threaten many species of ectotherms. Hawaii does not have any native amphibians or non-marine reptiles, yet introduced herpetofauna and native gobies may be affected by these pathogens. Given the largely recently assembled potential host community in Hawaii, we asked whether these globally important pathogens have also invaded. Ranavirus has not yet been surveyed in any ectothermic species in Hawaii. Bd has been documented in introduced Eleutherodactylus coqui frogs on Hawaii Island, but it has not been surveyed in other species or on other islands in Hawaii. We report on a survey of ranavirus and Bd in the 5 introduced frog species on the island of Oahu. We collected 11 adults and tadpoles of Dendrobates auratus and 20-30 individuals per life stage (including tadpoles, metamorphs, adults) from one or more populations of Rana rugosa, Rana catesbeiana, Bufo marinus, and Eleutherodactylus planirostris. Skin swabbing was done externally according to standard Bd sampling protocols. Frogs were humanely euthanized and necropsied, and samples of liver, intestine, and kidney were taken for ranavirus sampling. We extracted DNA from all samples and used qPCR to test for the presence of Bd in swab samples and ranavirus in organ samples.
Results/Conclusions
We found no evidence of ranavirus DNA in any of 327 individuals from all species. We found Bd in 3 out of 5 species (Rana catesbeiana, Bufo marinus, and Eleutherodactylus planirostris) and at 2 out of 6 sites sampled. Prevalence of Bd was low, with only 4 individuals testing positive in the entire study. Surveillance of these pathogens has the potential to contribute to managing introduced frog populations and native wildlife in Hawaii, and global amphibian populations via Hawaii’s role as a nexus for the movement of goods and people around the Pacific Rim. Since absence of ranavirus is rarely reported in the literature for any area harboring amphibians, Oahu may provide an opportunity to study spread and disease dynamics if the pathogen does arrive.