Assessing Amphibian Disease Risk in the Northeast

Science Center Objects

Disease in amphibian populations can have a range of effects, from devastating declines following introduction of a novel pathogen to recurring breakout events on a landscape. Elucidating mechanisms underlying the effects of diseases on amphibian populations is crucial to help managers make appropriate decisions to achieve management goals for amphibians.

The Challenge: Batrochytrium dendrobatidis (Bd), has been found in the Northeast for decades, while ranavirus may have been more recently introduced; both cause massive mortality in some species and sites. An emerging fungal pathogen, Batrachochytrium salamandrivorans (Bsal), has caused mass mortality events and severe population declines in European salamanders via introduction into wild populations from the pet trade. Introduction of this pathogen to North America could be devastating, not only to local populations but also to global salamander biodiversity.  However, little is known about how these diseases persist in habitats or the ability of individuals to clear infection. Elucidating mechanisms underlying the effects of diseases on amphibian populations is critical for helping managers make appropriate decisions to achieve management goals.

The Science: We have sampled for two diseases, Ranavirus and frog chytrid (Batrochytrium dendrobatidis, or Bd) on multiple refuges in the Northeast in conjunction with an analysis of soil contaminants to determine if local site factors can predict likelihood of disease outbreaks. ARMI is working collaboratively nationwide to determine the presence of Bsal in North American salamander populations in locations with increased risk of exposure to the Bsal pathogen. As part of a nation-wide study, NEARMI is monitoring a network of red-spotted newt populations (Notopthalmus viridescens) in a contiguous forest using mark-recapture techniques. Disease status of individuals and their use of habitat across the landscape is recorded through time.

The Future: Sampling for diseases such as Ranavirus and Bd will continue in the region, and Structured Decision Making workshops are underway to determine if refuges can collaboratively pursue amphibian management goals, including risk of disease. If Bsal is introduced to the Northeast, lessons learned from the study of Bd dynamics in amphibian populations can help inform management actions. In the interest of developing proactive management strategies, NEARMI’s research will help identify habitat conditions that may be useful for reducing population susceptibility.