Batrachochytrium

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

Infections with B. dendrobatidis are often 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 seem to play a role.

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

In larvae the keratinised mouthparts are affected. During metamorphosis the infections can lead to dramatically high mortality rates. The clinical signs are often non-specific and may affect the skin (often appear macroscopically unchanged or “dull” or depigmented; hyperkeratosis and excessive episodes of skin shedding, mixed infections with severe erosions of the skin) as well as the behaviour (atypical behavior, such as prolonged stay in the water, ataxia and CNS problems). Spontaneous deaths without previous clinical manifestation are also observed.

Differentiation:

Currently, there are six known distinct genetic Bd lineages. The most pathogenic seem to be fungi of the lineages BdCAPE and BdGPL (=Global Pandemic Lineage). BdCAPE is present mainly in Africa, while BdGPL is distributed worldwide and is the most commonly detected Bd lineage. Clinical symptoms are similar to the generally exhibited symptoms of chytrid fungus, including skin lesions. Affected animals also often present with neurological symptoms. This pathogen can cause severe outbreaks up to local extinctions of whole populations. Severity and extent of these outbreaks depend on different factors, including host species and environmental factors. Animals can be inapparent carriers of the disease. We are now offering a specific test for BdGPL as a differentiation option in samples with a positive Bd-PCR result.

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. Batrachochytrium salamandrivorans can also infect other salamanders, but has not yet been detected in anurans.