The Problem
Worldwide amphibian populations are facing an unprecedented decline that is, in part, caused by the chytridiomycosis disease. Chytridiomycosis is an emergent infectious disease that in amphibians is caused by two species of pathogenic chytrid fungi: Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). Bd and Bsal are aquatic, zoosporic, and saprobiontic fungi that degrade keratin to survive. Given that the keratin is one of the main components of the skin, these chytrids can seriously alter functionally and structurally amphibian’s skin, leading in many cases to animal death. Bd has been found infecting hundreds of species across the three amphibian orders (caecilians, frogs and salamanders) on every continent of their distribution range, whereas Bsal, with a most recent description, has been detected in urodeles (salamanders) affecting mostly continental European populations. The disease threat varies depending on fungi lineages, amphibian species/communities, and geographic region, leading to a complex system, in which, for instance, several genetically distinct lineages of Bd with different virulence have being described. One of these lineages, the Global Pandemic Lineage (GPL) is, without any doubt, an invasive species that have being actively spread all over the world mainly by international animal trade.
Our Proposal
Mitigation actions are critically needed to stop the spread of introduced chytrid lineages into new environments with probably lethal consequences for the native amphibians. Screening for the presence of the disease is one of the first mandatory steps of any mitigation plan, and it ideally should be done by an immediate and cost-effective method. Currently, the principal diagnostic of the chytridiomycosis is perfomed by the analysis of swab samples of amphibian skin or oral disc (the only keratinised body part in larvae) using real-time polymerase chain reaction (RT-PCR). While there are some portable devices that can perform RT-PCR or other genetic amplification methods allowing chytridiomycosis detection in near field locations, the availability of those devices is not guaranteed for all the researchers/rangers at each amphibian encounter, mainly due to the absence of the machine in their equipment, the lack of adequate training to run the reaction, or the relative high price of the PCR mix for the portable devices. Here, we propose the used of swabs with a pH sensitive indicator cotton tip that could enable at the same time the sampling and the detection of the chytridiomycosis. A simple color change in the swab tip could immediately reveal the presence of chytrid fungi at the very same field site. In addition, the proposed method would not require trained personnel and could be implemented everywhere without need of power and with an inexpensive cost.
We Assume that...
Although Bd and Bsal differ in their death mechanisms, both chytrid species have been reported to disrupt electrolyte homeostasis and fluid balance in the skin of the infected amphibians.
We assume that this imbalance causes a shift in the normal pH of the amphibian external epithelial surfaces, plausibly leading to a pH acidification.
Constraints to Overcome
To implement the use of pH sensitive swabs for chytridiomycosis screening, further research on the effect of chytrid infection on the amphibian skin pH is needed. The hypothesized pH change needs to be detected by the proposed technique in a standard and systematic way. As a result, it would require building a pH scale of amphibian skin of healthy and infected animals (at different pathogenic burden levels) from as many species as possible.
Current Work
After the project ideation phase, thorough search of possible materials that could fit with our requirements was done finding the first prototype of pH sensitive swabs, which were previously designed for detecting pH in wounds. Dr. Jaime Bosch, a world expert in chytridiomycosis and part of the project team, has tested the adequacy of these pH indicator cotton swabs in Midwife toad larvae. This first step allowed us to determine that the pH sensitive swabs are able to measure pH in amphibian samples. Besides, although we lack cause-effect proof, the sampled amphibians were positive to chytridiomycosis (checked by RT-PCR) and showed acid pH levels in their oral discs while living in a basic aquatic environment.
Current Needs
The Conservation X Tech Prize will be used to empirical test pH change in amphibian skin related to chytridiomycosis and, thereby, establish a new immediate detection method of the infection. Funding will cover pH sensitive swabs costs, and partially field and RT-PCR (to corroborate infection status of the samples) expenses. At least, two field journeys in two locations, Spain and Puerto Rico, will be carry out under the respective leadership of Dr. Jaime Bosch and Dr. Patricia Burrowes, also world expert in chytridiomycosis and project team member.