PLoS ONE 3, e2545 (2008)

Extreme weather can cause mass die-offs in the animal kingdom by altering host–pathogen relationships, according to researchers led by Craig Packer of the University of Minnesota in St Paul.

They found that high lion mortality in Tanzania in 1994 and 2001 seemed to be linked to severe drought followed by heavy rain. Blood work on lions suggested the following explanation: the drought-starved buffalo had heavy tick infestations after the rains, often killing them and providing carcasses for lions to scavenge. A coincident epidemic of normally non-fatal canine distemper virus suppressed the lions' immune systems, allowing the also normally harmless tick-borne blood parasite Babesia to reach fatal levels.