Global Spread of Chytrid Fungus Traced to Brazilian Bullfrog Trade Network

A century-old Brazilian fungus may have infected amphibians worldwide by hiding in the global frog meat trade network. Genetic evidence shows Batrachochytrium dendrobatidis (Bd-Brazil) was present in Brazil as early as 1916, predating commercial bullfrog introductions in the 1930s and 1970s.

Museum specimens from 1815 to 2014 confirm this strain’s presence in native species decades before global detections.

Researchers analyzed 2,280 preserved amphibian samples and mapped 3,617 trade routes across 48 countries.

Trade records reveal Brazil exported bullfrogs to the U.S. between 1991–2009, with subsequent U.S. exports to South Korea in 2004 and 2008. These routes align with the strain’s geographic spread.

Luisa P. Ribeiro, a study co-author, noted: 'This genotype is highly prevalent in different native Brazilian species, with very old records. When we look elsewhere, the records are much more recent and occur only in bullfrogs and other exotic species.'

The study, published in Biological Conservation (DOI: 10.1016/j.biocon.2025.111547), identified eight primary trade routes linking Brazil to global markets. While 500+ amphibian species are affected by chytrid infections, the study avoids quantifying mortality rates, emphasizing instead the role of trade infrastructure in pathogen dissemination.

The team cautions that further research is needed to assess the strain’s long-term ecological impacts.