Loss of wetland biodiversity increases disease risk in frogs

decrease font size  Resize text   increase font size       Printer-friendly version of this article Printer-friendly version of this article

Amphibians in species-poor wetlands have a higher risk of becoming infected with a virulent parasite than those in wetlands with a rich diversity of species, according to a Purdue University finding that sheds light on how biodiversity moderates the transmission of infectious diseases.

In wetlands with a wide variety of both amphibian and parasite species, Pacific chorus frogs are far less likely to become infected with Ribeiroia ondatrae, a trematode that causes limb malformations in frogs and newts.

"The loss of species diversity has major implications for how harmful and deadly diseases are transmitted in nature," said Jason Hoverman, an assistant professor of vertebrate ecology. "While the risk of getting infected with this trematode is largely a factor of how many trematodes are present in the community, we found that disease transmission is also impacted by the number of host species and other parasite species in the system."

The study addresses a paradox of disease ecology: In highly diverse communities, potential hosts are less likely to become infected with harmful pathogens, even though these communities contain more parasites overall. In complex wetland systems, frogs may carry a greater number of parasites, but hosts and parasites work in tandem to prevent infections by the most virulent pathogens. Reducing parasite diversity as well as host diversity greatly increases a frog's risk of contracting a crippling parasite such as Ribeiroia ondatrae.

The implications of losing biodiversity go beyond wetlands, Hoverman said.

"What is amazing is that we're finding these principles hold true for basically all disease systems, whether human, animal or plant. Because human activities are linked to the loss of biodiversity, there are growing concerns that we could inadvertently influence the emergence of infectious diseases."

About 43 percent of global amphibian populations are declining due to dwindling habitats and a rise in infectious diseases such as ranavirus and Ribeiroia ondatrae. To determine the relationships between disease transmission, amphibian diversity and parasite diversity, Hoverman and researchers from the University of Colorado combined data from 345 wetlands, a laboratory experiment and a controlled outdoor experiment.

"Most disease studies focus either on host diversity or parasite diversity," Hoverman said. "But what we were able to do here was bring those two things together so we could look at the relative contribution of changes in host and parasite diversity on disease risk."

In all three settings, higher host and parasite diversity resulted in fewer Ribeiroia ondatrae infections in Pacific chorus frogs. Increasing the number of amphibian species in a wetland reduced infections by Ribeiroia ondatrae and other parasites, a phenomenon known as the "dilution effect." Increasing the number of other parasite species further reduced trematode infections, highlighting the important role of parasites in regulating disease transmission, Hoverman said. The most diverse wetlands suppressed transmission of Ribeiroia ondatrae from ramshorn snails – the trematode's intermediate host - to frogs by more than 50 percent.

"We always think about the negative connotations of parasites, but having more parasites is not equivalent to greater disease risk," Hoverman said. "Most parasites are fairly benign. Disease risk is really defined as how many virulent parasites are in a community."

The paper, published in the Proceedings of the National Academy of Sciences, is available at http://www.pnas.org/content/110/42/16916.full

Buyers Guide

Doyle Equipment Manufacturing Co.
Doyle Equipment Manufacturing prides themselves as being “The King of the Rotary’s” with their Direct Drive Rotary Blend Systems. With numerous setup possibilities and sizes, ranging from a  more...
A.J. Sackett Sons & Company
Sackett Blend Towers feature the H.I.M, High Intensity Mixer, the next generation of blending and coating technology which supports Precision Fertilizer Blending®. Its unique design allows  more...
R&R Manufacturing Inc.
The R&R Minuteman Blend System is the original proven performer. Fast, precise blending with a compact foot print. Significantly lower horsepower requirement. Low inload height with large  more...
Junge Control Inc.
Junge Control Inc. creates state-of-the-art product blending and measuring solutions that allow you to totally maximize operating efficiency with amazing accuracy and repeatability, superior  more...
Yargus Manufacturing
The flagship blending system for the Layco product line is the fully automated Layco DW System™. The advanced technology of the Layco DW (Declining Weight) system results in a blending  more...
Yargus Manufacturing
The LAYCOTE™ Automated Coating System provides a new level of coating accuracy for a stand-alone coating system or for coating (impregnating) in an automated blending system. The unique  more...
John Deere
The DN345 Drawn Dry Spreader can carry more than 12 tons of fertilizer and 17.5 tons of lime. Designed to operate at field speeds up to 20 MPH with full loads and the G4 spreader uniformly  more...
Force Unlimited
The Pro-Force is a multi-purpose spreader with a wider apron and steeper sides. Our Pro-Force has the most aggressive 30” spinner on the market, and is capable of spreading higher rates of  more...
BBI Spreaders
MagnaSpread 2 & MagnaSpread 3 — With BBI’s patented multi-bin technology, these spreaders operate multiple hoppers guided by independent, variable-rate technology. These models are built on  more...

Comments (0) Leave a comment 

e-Mail (required)


characters left

Pacesetter Grain Hopper

The Pacesetter Gain Hopper features original and innovative ideas like the patented RollerTrap™, the industry’s easiest to open and maintain trap ... Read More

View all Products in this segment

View All Buyers Guides

Feedback Form
Feedback Form