Ticks and the diseases they vector are a growing problem in North America, with the northeastern US and southeastern Canada emerging as a critical hotspots in the for human infections. Complicating the problem are emergent tick-borne diseases, the recent invasion in 13 states of Asian Longhorned tick (Haemaphysalis longicornis), and the revelations that native ticks are expanding their ranges. Controlling tick-borne disease transmission is paramount and calls for multidisciplinary solutions. So far chemical acaricides, various types of vaccinations, and fungal approaches have been the primary focus; however, a small group of forest ecologists in the eastern US have begun studying how ticks respond to prescribed fire, which has recently been shown to dramatically reduce tick populations in the southeast.
Interestingly, this may actually be old news. Putting together what we now know about ticks and the history of fire in the eastern US, it’s possible that fire previously helped keep ticks and their diseases at bay in previous times. As early as 1754, it was noted around the Delaware Bay that intentional burning was beneficial for reducing ticks, and that eliminating fire seemed to allow the proliferation of ticks. A growing breadth of fire history research, using methods like tree ring analysis and analysis of sediment cores from lakes and ponds, has illustrated that fire was in fact more prevalent before the 1940s throughout the eastern US. Furthermore, burning historically occurred in varying seasons which could have been important for killing different species or life stages of ticks in seasons that they would have been most susceptible. As evidenced by tree ring records, fire frequencies with intervals of 1-20 years were common throughout the eastern US, but in the past century have dramatically increased to intervals > 50 years. The removal of this stressor for tick species and the subsequent mesophication of eastern forests (i.e. more dense, cooler and wetter) has likely eliminated an important cause of mortality for tick populations (fire) while improving both tick habitat and interaction between ticks and wildlife hosts.
Inspired by research from the southeastern US highlighted earlier this year by NAFSE (see Dr. Elizabeth Gleim’s exciting webinar on ticks and prescribed fire here) that showed a strong reduction of ticks from prescribed fire in southern pine forests, a new team of researchers has come together in the New Jersey Pinelands to study how fire and fire quality may provide important mechanisms to reduce ticks and tick-borne disease. This team, led by Drs. Jesse Kreye of Penn State University and Michael Gallagher of the USDA Forest Service Northern Research Station, also includes experts from the Rutgers Center for Vector Biology and the New Jersey Forest Fire Service, and is utilizing numerous burned and unburned sites to study changes in tick abundance, disease prevalence, and habitat quality that arise from different severities of fire. Although this work is ongoing, Gallagher and Kreye will be presenting some interesting preliminary results from the first year of this work in a special session at the upcoming Fire and Forest Pests workshop in Portland, ME this January. The team plans to continue this work through time to see how fire’s effects on ticks play out in relation to current and historic prescribed burn intervals. The results of this work will help to better understand the natural ecology of ticks and inform how the use of prescribed fire may help control the problems caused by ticks in the northeast US and elsewhere.