Chytrid fungal disease of amphibians: A new fuel to the fire of Indian Amphibian Conservation?
Keerthi Krutha, Neelesh Dahanukar, Sanjay Molur
Chytridiomycosis, an emerging infectious disease of amphibians, was not reported from the Western Ghats (WG) until recently. The need of a systematic study of the disease across the ecologically sensitive region of the WG was urgent. This study aimed to understand the extent of occurrence and spread of this disease across the Western Ghats and standardize non-invasive sampling methods which will permit for long term monitoring of the disease.
Sampling of Chytrid fungus (Batrachochytrium dendrobatidis; Bd) was carried out using a non-invasive method. Cotton swabs were used for collection of zoospores from frog skin. DNA extracted from swabs and tested using a nested PCR technique with two Bd specific primer sets. The positive samples were analyzed using Quantitative PCR to determine the number of zoospore per sample. Histopathology of the skin was performed to confirm the presence of disease.
Random sampling was carried out across nineteen locations, distributed within the states of Goa, Karnataka and Tamil Nadu 400 swab samples were collected. Standardization of protocols for DNA extraction from swabs, nested PCR and quantitative PCR is complete. Five species of amphibians have tested positive for the fungus, across five locations in the Western Ghats with zoospores amounting to an average of 23.
Chytridiomycosis has resulted in extinctions of more than 200 populations of amphibians worldwide. Information on disease threats to amphibians within Indian sub-continent is inadequate with only one previous report of the disease on an endemic anuran from Peppara WLS in Kerala. There is an urgent need to understand the occurrence and spread of the disease and setup of long term amphibian population monitoring programs to prevent extinctions of amphibian species.