Hidden Hosts

A fungus that has killed amphibians around the world also infects crayfish, which may be helping to spread the disease, scientists report.

The fungus, Batrachochytrium dendrobatidis, has afflicted hundreds of species of frogs and other amphibians. But the pathogen continues to linger even when no amphibians are around. Scientists have suspected that other organisms — so-called “reservoir hosts” — might carry the fungus and later infect amphibians.

A research team found crayfish that tested positive for B. dendrobatidis at sites in Louisiana and Colorado. The fungus appeared to have taken up residence in the animals’ gastrointestinal tracts, according to the study in Proceedings of the National Academy of Sciences. A survey of more than 9,000 amphibians at 97 Colorado wetlands revealed that wetlands containing crayfish were more likely to have B. dendrobatidis-positive amphibians.

In the lab, the fungus survived longer when provided with carapaces or gastrointestinal tracts of crayfish. Infected crayfish could also transmit B. dendrobatidis to tadpoles. And some crayfish continued harboring the fungus for as long as three months. People often transport crayfish for bait, food, and aquariums, which “could rapidly move B. dendrobatidis great distances and contribute to the global B. dendrobatidis pandemic,” the authors write. Roberta Kwok | 17 December 2012

Source: McMahon, T.A. et al. 2012. Chytrid fungus Batrachochytrium dendrobatidis has nonamphibian hosts and releases chemicals that cause pathology in the absence of infection. Proceedings of the National Academy of Sciences. doi: 10.1073/pnas.1200592110.

Image © Eric Isselee | Shutterstock.com