Field experiments on the effects of fire on parasite transmission to amphibian hosts

The emergence of infectious diseases is often associated with changes to host-pathogen ecology, and wildfires are known to profoundly modify the ecology of terrestrial and freshwater ecosystems. Nevertheless, few studies have employed manipulative experiments to quantify the effects of fire on infections across parasite species. In a mark-recapture study, prescribed burns did not significantly affect the densities of Cuban tree frog (CTF; Osteopilus septentrionalis) definitive hosts. However, prescribed burn field experiments and a before-after-control-burn mesocosm study revealed that fire decreased a skin-penetrating nematode in CTFs by killing the parasite's soil-dwelling, free-living stage, with hotter fires causing a greater reduction in soil-dwelling nematodes. Additionally, prescribed burns were associated with increases in a terrestrial acuariid nematode and several aquatic trematode metacercariae in CTFs, likely by increasing intermediate host densities. Seven years after the burns, we found little evidence of full recovery because the trajectories of these parasites did not show clear signs of flattening. These results suggest that fire can have predictable and long-term direct and indirect positive and negative effects on parasite transmission.