There are two distinctly different life stages for BD: the motile, flagellated zoospore and the reproductive thallus
The zoospore is free living and swims through water with its tail-like flagellum. Once in contact with the amphibians skin, the zoospore enters a keratinized skin cell. The exact mechanism of entry into the cell is unknown to date.
Once inside, the development of the thallus begins. The thallus is the form in which the fungus lives in the frog and is what ultimately kills it. It develops zoosporangium, zoospore factories. Via discharge tubes these zoospores are released into the environment.
It is not fully understood how BD disperses, but it is presumed it is via skin to skin contact between infected frogs during mating, fresh zoospores in the environment, or a combination of both.
Rosenblum et al. (2008) PNAS, 104 (44), 17034-17039
Amphibian Chytridiomycosis 