The chytrid fungus Batrachochytrium (B.) dendrobatidis was first identified in Australia in 1998 and named in 1999. This fungus is thought to be responsible for the population decline and the global extinction of >200 amphibian species.

Infections with B. dendrobatidis are in many cases associated with very high mortality rates (in lab up to 100%), but the fungus is not necessarily lethal. Other factors such as stress or co-infections with other pathogens also appear to play a role.

B. dendrobatidis multiplies in keratinized tissue and therefore affects primarily the outer skin of adult animals (stratum corneum to the stratum granulosum).

In larvae the horn strips on the mouth are affected. During metamorphosis the infections can lead to dramatic high mortality rates. The clinical symptoms are often nonspecific and may, in addition to the skin (often appear macroscopically unchanged or "blunt" or depigmented; hyperkeratosis and massive skinning episodes, mixed infections with severe erosions of the skin) or behavial changes (atypical behavior, such as prolonged stay in the water, ataxia and CNS problems). Spontaneous deaths without previous overt clinical disease are also observed.

Batrachochytrium salamandrivorans is a recently described highly-contagious and deadly chytrid fungus that has massively infested and killed fire salamanders especially in North-west Europe.

Infected animals show anorexia, apathy and ataxia as well as skin lesions with superficial erosions and deep ulcerations all over the body.Suitable test materials are skin biopsies and swabs.