Chytrid Research in Asia Falls Behind, But New qPCR Test Shows Alarming Levels in Indian Amphibians
Image Source: The Mandarin
A devastating fungal disease has decimated frog populations for 40 years, causing 90 species to go extinct. Unlike the global COVID-19 pandemic, this "panzootic" remains largely unknown. However, a recent multinational study has developed a method to detect all known strains of the disease, caused by the amphibian chytrid fungus. This breakthrough will greatly enhance our ability to detect and study the disease, with the goal of finding a widely accessible cure.
A significantly high death rate.
Chytridiomycosis, or chytrid, has caused devastating declines in over 500 frog species, leading to 90 extinctions, including seven in Australia. It is the deadliest animal disease known, infecting frogs by reproducing in their skin. The fungus damages the skin, disrupting water and salt balance and eventually causing death. Chytrid originated in Asia and spread globally through amphibian trade. Frog species without evolutionary resistance suffered mass mortalities upon exposure. The culprit was identified in 1998, prompting research on infection trends and frog protection. However, detecting chytrid reliably remains crucial for tracking and addressing the disease.
Flawed swabbing technique
Researchers use a swabbing technique similar to COVID-19 testing, known as quantitative polymerase chain reaction (qPCR), to detect chytrid in frogs. Developed in 2004, the test swabs the frog's skin and measures the DNA volume of the target species. However, the existing test could not detect chytrid in its Asian region of origin due to divergence between Australian and Asian strains. A team led by researchers in India has developed a new qPCR test that successfully detects Asian chytrid strains. Collaborating with scientists in Australia and Panama, they also confirmed the test's reliability in those countries and its ability to identify a closely related chytrid species infecting salamanders. The new test is more sensitive, enabling detection of even low infection levels and expanding the range of species that can be studied.
Natural Immunity?
Some amphibian species carry the chytrid fungus without getting sick, thanks to natural immune resistance. Frog immunity is complex and could involve various factors such as chemicals in the skin, symbiotic bacteria, white blood cells, and antibodies. However, there is no clear correlation between resistance and immune function. Additionally, chytrid can suppress the host's immune response, making matters more complicated. Asia lags in chytrid research due to difficulties in detection, but a new qPCR test successfully detected high chytrid levels in Indian amphibians. Studying chytrids in their region of origin could provide insights into how Asian species developed resistance, potentially aiding the development of a cure for affected species in other parts of the world. While validation and promotion of the qPCR test are necessary, future work will analyze samples from Europe and Brazil to understand chytrid divergence. This detection method could be a vital step towards saving frogs, cherished inhabitants of our forests and wetlands.
Highly informative
Very informative article....