Climate extremes promote fatal co-infections during canine distemper epidemics in African lions

This study resolved a long-standing puzzle: why the 1994 Serengeti CDV epidemic was lethal while earlier CDV exposures left lions seropositive but alive. By integrating decades of serology, climate records and necropsy data, the authors showed that severe drought concentrated Babesia tick-borne blood parasites in debilitated buffalo prey. Lions feeding on them acquired unusually high Babesia loads, and the combination of immunosuppressive CDV plus heavy Babesia parasitemia produced fatal anemia. The work demonstrated that the same virus can be benign or deadly depending on co-infection and environmental context, and it explicitly linked extreme climate events to wildlife epidemics. It remains a key example of disease emergence as an interaction among pathogens, hosts and climate rather than a single-agent phenomenon.