Occurrence of the amphibian chytrid fungus Batrachochytrium dendrobatidis in introduced and native species from two regions of France

To investigate the occurrence of the amphibian chytrid fungus Batrachochytrium dendrobatidis ( Bd ) in France, we examined 575 amphibians collected between 1875 and 2008 for the presence of the infection in the epidermis. We confirmed Bd in seven of the 15 stations investigated in the Aquitaine and Poitou-Charentes regions. Histological examination revealed the presence of the infectious agent associated with mild epidermal changes in 25 of 493 (5.1%) amphibians sampled in 2007-2008. The overall occurrence was 21.9% (21/96) in the introduced American bullfrog ( Lithobates catesbeianus ) and 2.3% (4/172) in the native European water frog complex ( Pelophylax sp.). These prevalence data should be viewed as conservative giving the limitation of histology. Morbidity and mortality attributable to chytridiomycosis were not observed in these two species during this period. The introduced African clawed frog ( Xenopus laevis ) and all native museum specimens tested negative for chytrid infection. Unlike L. catesbeianus , Pelophylax sp. is broadly distributed at local and regional scales and whether or not this complex could act as a reservoir host in the dissemination of Bd remains to be determined. The presence of the chytrid fungus in amphibian populations from different locations in southwestern France calls for disease surveillance and for precautionary measures to avoid the spread of this emerging disease.