COS 108-4 - Wildfire disturbance initially increases Lyme disease risk in California, yet dampens disease risk through time

Wednesday, August 9, 2017: 2:30 PM
D137, Oregon Convention Center
Andrew J. MacDonald1, David W. Hyon2, Akira McDaniels2, Kerry O'Connor3, Andrea Swei4 and Cheryl J. Briggs5, (1)Biology, Stanford University, Stanford, CA, (2)UCSB, Santa Barbara, CA, (3)San Francisco State University, San Francisco, CA, (4)Biology, San Francisco State University, San Francisco, CA, (5)Dept. of Ecology, Evolution & Marine Biology, University of California, Santa Barbara, Santa Barbara, CA

Identifying the effects of human-driven perturbations, such as species introductions or habitat fragmentation, on the ecology and dynamics of infectious disease has become a central focus of disease ecologists. Yet, comparatively little is known about how zoonotic disease systems respond to catastrophic disturbance events like wildfires or hurricanes. In California, wildfire disturbance is centrally important to the ecology of forests and oak woodlands, and is projected to increase in severity and extent under future climate change. Here, using a recent wildfire as a natural experiment, we investigate the effects of wildfire disturbance on the ecology of Lyme disease in California oak woodlands.


We find that wildfire increases the abundance of questing adult and nymphal blacklegged ticks (Ixodes pacificus) in the year following fire, but that vector tick abundance declines sharply in the following two years. We find that the abundance of dilution hosts (western fence lizards) is unaffected by fire, but that the abundances of important reproductive hosts (deer) for ticks and amplification hosts (dusky-footed woodrats) for the Lyme bacteria (Borrelia burgdorferi) are significantly negatively affected by fire. We also found infected ticks and hosts only within the burn extent and only in the year immediately following the wildfire. In aggregate, due to the differential effects of this catastrophic disturbance event on different key host species and vector tick life stages in the transmission of B. burgdorferi, we conclude that wildfire initially amplifies Lyme disease risk in the first year following fire in California, but that risk is dampened substantially in following years due to tick population reductions and loss of key reservoir hosts from the system.