Global meta-analysis shows that immunisation reduces amphibian susceptibility to the chytrid fungus

Meng-Han Chung, Richard P Duncan, Daniel W.A. Noble, Benjamin Scheele, Simon Clulow

Emerging infectious diseases are increasingly impacting vertebrates, sometimes causing severe population declines. Chytridiomycosis, a lethal disease caused by the pathogen Batrachochytrium dendrobatidis (Bd), is among the most devastating, responsible for global amphibian collapses and extinctions. Developing strategies that improve host survival in the presence of Bd has therefore become a conservation priority. We conducted a meta-analysis to evaluate whether immunising individuals reduces disease susceptibility. Using 208 effect sizes from 53 experiments across 36 studies and 22 species, we compared infection prevalence, infection intensity, and mortality between experimentally immunised and non-immunised individuals subsequently exposed to Bd, representing the first such synthesis for a major emerging wildlife disease. Immunisation using live pathogens reduced host infection intensity and lowered mortality after re-exposure, whereas immunisation using Bd-derived natural chemicals reduced infection prevalence. Other immunisation approaches showed no clear effects across species. Immunisation effects also varied across disease progression stages, host life stages, and taxonomic groups. Our findings suggest that live-pathogen immunisation can be an effective strategy for increasing survival during reintroductions.  Management actions that supplement immunised individuals or help wild amphibians clear infections may enhance survival in vulnerable populations.