About This Project

A fungal pathogen spread around the globe by human activities now threatens many amphibians, including boreal toads, a high elevation specialist in the Rocky Mountains. In the lab, we increased toad survival by 40% when we applied a native fungus-fighting bacteria as a probiotic treatment. We are moving this probiotic method from the lab out into the field to assist wild boreal toad populations currently undergoing an epidemic infection caused by the fungus.

Ask the Scientists

What is the context of this research?

Lethal fungal diseases are increasingly affecting wildlife ranging from amphibians to bats and snakes, and many are the result of accidental introductions stemming from human activity (Fisher et al. 2012, McKenzie & Peterson 2012). We have limited tools to mitigate these fungal pathogens because approaches such as vaccines or antifungal drugs are not feasible for wild populations. Probiotic treatments (the use of beneficial, pathogen-inhibiting, symbiotic microbes) offer an innovative approach that can be lower cost and non-toxic (McKenzie et al. 2018). The amphibian skin microbiome system is at the forefront of this research and we are in a unique position to translate success in the lab to wild populations that are currently under threat from disease.

What is the significance of this project?

The boreal toad lives at high elevation in the Rocky Mountains and is threatened in Colorado by the same chytrid fungus that is affecting amphibians around the world. Boreal toads live more than 20 years and were once abundant members of these alpine wetland systems. In the lab, we have used a bacteria native to the toads as a probiotic to boost their skin defenses and survive fungal infection (Kueneman et al. 2016). Animals that survive may develop stronger immune defenses over time. We propose to apply this probiotic to a wild population that is currently experiencing a fungal disease epidemic in Chaffee County Colorado. Using native bacteria to boost animals' defenses against disease in the wild represents a novel approach to conservation.

What are the goals of the project?

We are conducting a probiotic trial on wild boreal toads at a site in central Colorado. We are testing different probiotic application methods such as which life stage to target, treating their water versus soil, or bathing them directly in a probiotic solution. The goal is to determine which application method allows the most probiotic to establish on the skin and persist the longest, to provide better disease protection. In August 2018, we will enroll 200 tadpole toads (100 control and 100 treated) for two weeks. Each toad will be swab sampled before and after treatment, marked, released, and monitored. During Sept-May we will analyze samples in the lab. Next year we will survey and sample more individuals to examine persistence of treated versus control toads.