Evaluating environmental DNA-based quantification of ranavirus infection in wood frog populations

A variety of challenges arise when monitoring wildlife populations for disease. Sampling tissues can be invasive to hosts, and obtaining sufficient sample sizes can be expensive and time-consuming, particularly for rare species and when pathogen prevalence is low. Environmental DNA (eDNA)-based detection of pathogens is an alternative approach to surveillance for aquatic communities that circumvents many of these issues. Ranaviruses are emerging pathogens of ectothermic vertebrates linked to die-offs of amphibian populations. Detecting ranavirus infections is critical, but nonlethal methods have the above issues and are prone to false negatives. We report on the feasibility and effectiveness of eDNA-based ranavirus detection in the field. We compared ranavirus titres in eDNA samples collected from pond water to titres in wood frog (Lithobates sylvaticus; n = 5) tadpoles in sites dominated by this one species (n = 20 pond visits). We examined whether ranavirus DNA can be detected in eDNA...