With the purpose of monitoring the health of amphibian populations in a more active way, the CCWHC has sought the collaboration of scientists and other professionals involved in research, monitoring and conservation of aquatic environments. We are lucky to be housed in the University of Prince Edward Island (UPEI), where the Biology Department includes researchers and academics with a keen interest and long experience working in both fresh and salt water ecology and toxicology. At the beginning of 2009, a working group was established and included María Forzán and Darlene Weeks (CCWHC), Natacha Hogan and Kevin Teather (Faculty of Science, Biology Dept., UPEI).
The group, recently named the "Amphibian Health Research Network" (AHRN), was formed to foster collaboration between pathologists, biologists, conservation officers and organizations, and any other individual or group interested in amphibian health. In particular, our goal for 2009 is to look for the presence of the chytrid fungus, Batrachochytrium dendrobatidis (B.d.), in the wild frog populations of the island. We have been fortunate to receive help from Rosemary Curley (PEI Dept. of Fish and Wildlife) , advice on sampling locations from Wayne Petley (Atlantic Veterinary College, Aquatic Facilities), data analysis from Raphael Vanderstichel (Atlantic Veterinary College, UPEI), monetary support from the Prince Edward Island (PEI) Wildlife Conservation Fund, and the collaboration and good will of many PEI residents who allowed us access to their ponds - and often told us we were welcomed to go for a swim in them..
Amphibian populations worldwide are threatened by the emergence and spread of the pathogenic, virulent and highly transmissible infection with B.d., which causes the disease known as chytridiomycosis. Chytridiomycosis is a major threat to captive and wild amphibians and is the cause of decline or extinction of up to 200 species of frogs. Action plans involving public awareness, surveillance and quarantine measures have been developed in Australia, one of the countries most severely affected. Chytridiomycosis has been reported in North America, including Nova Scotia and New Brunswick. As of March 2009, there was no information regarding the presence of chytridiomycosis in frogs in Prince Edward Island.
The objective of the Amphibian Health Research Network for 2009 is to determine if B.d. is infecting amphibians on PEI and whether infection differs by location, species, developmental stage and sex. We will also like to foster awareness among the public and special interest groups regarding disease status of amphibians and the potential consequences of infectious disease to the health of wild populations. We hope to work in conjunction with PEI Fish and Wildlife in establishing measures to reduce the risk of introduction of chytridiomycosis from neighbouring provinces and from frogs shipped internationally as pets or to limit the spread within PEI.
How? The way in which we are looking for the fungus is to capture wild frogs and gently rub a cotton swab on their skin. The swab is then placed in alcohol to preserve the sample, and shipped to Pisces Molecular, a lab in the United States where it can be determined whether B.d. is present or absent through a molecular technique known as PCR.
The frogs are also sexed (when possible), aged, measured and weighed, and then placed back in the pond. The whole process of sampling is very quick and harmless. As it is not possible to tell just by visual examination of a frog whether it is infected with B.d., we are very careful to disinfect our tools in between frogs, as we would not want to be responsible for inadvertently transmitting the fungus from frog to frog or pond to pond.
We were able to swab 114 individuals from ponds across PEI, mostly adult frogs, but also a few froglets and tadpoles, and have sent away the swabs for analysis. The species most frequently captured reflect which habitat they are most likely to be found in. Green frogs were the most frequently sampled as they like to stay along the edges of ponds through the summer. Fewer samples came from northern leopard frogs since the adults like to live in the grass around the ponds after breeding and are practically impossible to spot once there. A single sample came from a wood frog, an unexpected find as they tend to go back to the forest after mating in the pond. Serendipitously, on our first trip to a pond in the west part of the Island, we saw a single dead frog, a wood frog, floating in the water. We took the frog back with us in a container with fixative and treated it as a regular submission. To our surprise, the frog was severely infected with B.d., which likely caused its death. We have not seen dead frogs during any of our other sampling trips, to that pond or any other.
All in all, we tested a total of 115 frogs from 18 ponds across PEI. They were 93 green frogs, 20 northern leopard frogs and 2 wood frogs.
RESULTS FOR THE 2009 SURVEY:
Thirty-one frogs were positive the B.d. fungus (25 green, 5 leopard and 1 wood frogs). The overall prevalence of B.d. infection on the Island was 26.3%. Green frogs carried a heavier load of the fungus than leopard frogs. Young green frogs (froglets) carried a heavier load of fungus than the adults did. Other than 1 wood frog that was found dead from chytridiomycosis, none of the frogs swabbed looked sick.
These results were included in the presentations of the Amphibian Week, organized by the Wildlife and Exotics Club of the AVC, Oct 5-9, 2009. Speakers included Gillian Gouchie (co-President of the Club), Dr. María Forzán (CCWHC), Dr. Natachan Hogan (UPEI) and Dr. Richard Wasserug (Dalhousie Universtity, Nova Scotia).
What this means in the grand scheme of things is yet to be determined. It is possible for B.d. not to be as damaging to frogs that live in climates such as we have in Atlantic Canada - the fungus likes temperate conditions, not extreme heat or cold, and this may work in favor of frogs here on PEI. The more we look into this, the more likely we are to answer questions regarding the effect an infection with B.d. has on frogs living in cold countries.
By: María Forzán, October 7, 2009