Potential role of ranavirus in eastern hellbender declines

The eastern hellbender (Cryptobranchus alleganiensis alleganiensis) of North America is declining in several watersheds, and long-term surveillance studies reveal that one reason for declines is a lack of recruitment. Streams... [ view full abstract ]

The eastern hellbender (Cryptobranchus alleganiensis alleganiensis) of North America is declining in several watersheds, and long-term surveillance studies reveal that one reason for declines is a lack of recruitment. Streams with declining hellbender populations contain viable eggs, but larvae are missing. There may be several contributing factors, including pathogens. Ranavirus is a global emerging pathogen that is known to infect hellbenders; however, reports of ranaviral disease in giant salamanders have been limited to the Chinese giant salamander (Andrias davidianus) in farm settings. Our goal was to investigate the susceptibility of eastern hellbenders to ranavirus under various controlled experimental conditions, including temperature, co-infection, and contaminant exposure. To date, we have exposed larval hellbenders to ranavirus at two water temperatures (15 and 22 °C). We also exposed juvenile hellbenders to environmentally relevant concentrations of ranavirus, Batrachochytrium dendrobatidis (Bd), and these pathogens in combination with each other and with 6 ppm glyphosate pesticide. We found that hellbender larvae were susceptible to ranavirus at 22 °C (75% died) but not 15 °C (0% died). Histopathological lesions included organ necrosis (particularly the spleen, hematopoietic tissue, and vessel walls) and cutaneous polyps. Juvenile hellbenders were similarly susceptible to ranavirus but exposure to Bd caused no mortality, and concurrent exposure of Bd or glyphosate pesticide with ranavirus did not significantly increase mortality in comparison to the ranavirus only treatment. We also found that juvenile hellbenders could withstand high concentrations of glyphosate (Round-up® formulation). These initial results suggest that ranavirus may be an important factor affecting recruitment of larval and juvenile hellbenders into the adult age class.