Pathogen Affecting Tadpoles Found Worldwide

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Scientists have found a microbe called a protist infecting the livers of tadpoles in a variety of habitats across four continents. Denis Balibouse / Reuters

Amphibians are in trouble. According to the International Union for Conservation of Nature, 41 percent of amphibians are at risk of extinction, threatened by habitat loss, environmental degradation and introduction of invasive species. Disease also plays a role. Fungal and viral pathogens have caused massive die-offs of adult frogs and toads worldwide. Now researchers have found a single-celled microbe called a protist infecting the livers of tadpoles in a variety of habitats across four continents.

Some tadpoles affected by this microbe have shown signs of being bloated, lethargic and having hemorrhages in their skin, and the protist has caused die-offs of several species in the United States.

Scientists from the University of Exeter and elsewhere examined tadpoles using a DNA test to look for the presence of a protist already known to infect tadpoles in the United States. They found evidence of the microbe in the liver of tadpoles in the two African countries of Cameroon and Tanzania, French Guiana (in northeastern South America), the African island of São Tomé and the United Kingdom. These tadpoles live in a variety of different environments, tropical and temperate, high and low altitudes, which suggests that the protist is fairly adaptable and probably found throughout much of the world.

"We now need to figure out if this novel microbe—a distant relative of oyster parasites—causes significant disease and could be contributing to the frog population declines," said Thomas Richards, from the University of Exeter, in a statement.

The protist does not always affect tadpoles negatively, with some infected amphibians failing to show symptoms. It's unclear exactly how big of an impact the protist is having, according the study, published August 11 in Proceedings of the National Academy of Science, but the scientists hope to find out in subsequent research.

Pathogen Affecting Tadpoles Found Worldwide | Tech & Science