Batrachochytrium

Batrachochytrium is a genus of fungi in the phylum Chytridiomycota that includes two notable amphibian pathogens: Batrachochytrium dendrobatidis (Bd) and Batrachochytrium salamandrivorans (Bsal). These chytrids cause chytridiomycosis, a skin disease linked to widespread declines and extinctions of amphibian populations worldwide.

Bd and Bsal have a life cycle that features motile zoospores and thick-walled sporangia that develop in the keratinized epidermis of amphibians. Zoospores are released into water, swim to a host, encyst in the skin, and reproduce, emitting new zoospores. Infection disrupts skin function, impairing osmoregulation and respiration, which can be fatal, especially in individuals with thinning or damaged skin.

Bd has a near-global distribution, detected in many continents and a wide range of habitats. Bsal has spread from introduced populations in Europe and has been detected in North America and other regions as monitoring continues. Both pathogens pose substantial conservation risks, particularly to species with limited ranges or highly specialized skin.

Diagnosis and monitoring rely on skin swab sampling followed by PCR-based assays to detect chytrid DNA. Clinical signs in affected animals include abnormal skin shedding, thickened or discolored skin, lethargy, and impaired movement; infections can be subclinical in some cases.

Conservation and management emphasize surveillance, biosecurity to prevent spread, and treatment of infected individuals in captivity with antifungal agents such as itraconazole baths. Ongoing research explores field-ready mitigation, host resistance, vaccines, and strategies to reduce environmental and ecological stressors that exacerbate disease impacts.