Preliminary Analysis of Historical Evidence of Fungal Pathogen in Amphibians in the Los Angeles Region

The recent emergence of the fungal pathogen, Batrachochytrium dendrobatidis (Bd), has resulted in outbreaks of the disease, Chytridiomycosis, in amphibian populations around the world and is a major factor in the worldwide decline of amphibians. The emergence of this disease has brought about different hypotheses regarding the origin of this pathogen. One hypothesis proposes that Bd was first spread through the international trade of Xenopus laevis, the African-clawed frog. This hypothesis is contingent on evidence of the earliest known Bd infection in a specimen of Xenopus laevis from 1931 and proof of stable endemic infections throughout sub-Saharan Africa.  The objective of this study is to investigate whether this hypothesis may hold true by examining specimens of X. laevis imported to Los Angeles County, California, where X. laevis was released into the wild in the 1960’s after being used as laboratory animals for human pregnancy testing. Swabbing of native amphibian specimens from the Los Angeles region was conducted at the California Academy of Science in San Francisco, California, USA. We extracted DNA from swabs, followed by analysis by real-time PCR. Our results help explain how the transport of X. laevis into Los Angeles may have facilitated the spread of Bd into native amphibians in Los Angeles. Histological analysis of the same specimens may confirm Bd infection of the specimens which tested positive by PCR.