About This Project

Amphibians are experiencing a global extinction event. Nearly 200 species are thought to be extinct, and two-thirds of amphibian species are threatened with extinction. The Chytrid fungus has received a lot of attention, while the deadly ranavirus has been overlooked. We will develop a way to determine if a ranavirus outbreak has occurred by detecting how much DNA from the virus is in wetlands (this DNA is called environmental, or eDNA).

Ask the Scientists

What is the context of this research?

Ranaviruses have a global distribution. They have caused population declines in amphibian species because when an outbreak occurs hundreds of animals die very rapidly. However, researchers don't know the spatial distribution or temporal frequency of these disease events. eDNA can help us address this gap in our knowledge.

Environmental DNA (eDNA) is DNA that is detected in environmental samples like soil and water. Ranavirus is waterborne, so its DNA will be detected in the water samples we collected. A recent study used eDNA to show that viral DNA in water increases during an outbreak. This means that using eDNA to detect the virus in water can be used as an effective monitoring tool; however, more work is needed to fully develop this tool.

What is the significance of this project?

All amphibian populations are threatened by the world-wide emergence of ranaviruses. However, many conservation actions are costly. Therefore, environmental agencies need to know where this disease occurs most frequently to focus research and conservation efforts. Often, monitoring for this disease requires tissue samples to confirm ranavirus infection. Getting tissue samples is lethal; and trapping amphibians can cause stress and unintended mortality. These negative effects need to be minimized in populations with endangered species. eDNA is cost-effective compared to traditional field techniques and can be used in any amphibian population without disturbing the animals. Using eDNA to detect ranavirus can tell land managers where resources are most needed to save amphibian populations.

What are the goals of the project?

Our goal is to develop a way to use eDNA to monitor freshwater wetlands for ranavirus. To do this, we need to determine how frequently a water sample is required to positively detect a ranavirus outbreak, and estimate the background detection rate.

We will estimate the sampling frequency and the background detection rate by extracting eDNA from 100 water samples that were collected in 2017. We will measure how many copies of virus DNA were in the sample using a method called quantitative polymerase chain reaction (qPCR). We will select 20 samples during the period before any disease was detected to estimate the background prevalence, and the remaining 80 samples will be used to analyze trends in ranavirus abundance. These trends will tell us how often a sample is required for monitoring.