Experimental infection of self-cured Leiopelma archeyi with the amphibian chytrid Batrachochytrium dendrobatidis

The susceptibility of Archey's frog Leiopelma archeyi to Batrachochytrium dendrobatidis (Bd) is unknown, although one large population is thought to have declined sharply due to chytridiomycosis. As primary infection experiments were not permitted in this endangered New Zealand species, 6 wild-caught L. archeyi that naturally cleared infections with Bd while in captivity were exposed again to Bd to assess their immunity. These frogs were from an infected population at Whareorino, which has no known declines. All 6 L. archeyi became reinfected at low intensities, but rapidly self cured, most by 2 wk. Six Litoria ewingii were used as positive controls and developed heavier infections and clinical signs by 3 wk, demonstrating that the zoospore inoculum was virulent. Six negative controls of each species remained uninfected and healthy. Our results show that L. archeyi that have self cured have resistance to chytridiomycosis when exposed. The pattern is consistent with innate or acquired immunity to Bd, and immunological studies are needed to confirm this.