Deer: supplemental feeding may reduce tick populations

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The prevalence of ticks and tick-borne diseases has increased over the past decade in the United States and the cause of the increase is unclear. However, it could be a result of changing habitat due to management actions, such as supplemental feeding or prescribed fire regimes (controlled burning to reduce wildfire risk and manage ecosystems).

Hunters and wildlife management experts use supplemental feeding to help improve the general condition of animals on properties, provide food when it’s scarce, and concentrate animals for recreational purposes; it has been linked to changes in local vegetation and increased wildlife visitation rates.

A study published in the Journal of Vector Ecology set out to determine how the presence of supplemental feeders influenced local populations of ticks and tick hosts.¹

Researchers sampled 17 privately-owned properties with established deer feeders throughout Mississippi. The researchers collected ticks using carbon dioxide baited traps with dry ice in vented coolers and double-sided tape. (Carbon dioxide baiting is one of, if not the most, effective trapping technique for ticks in the southeastern U.S.) For each of the feeder sites tested, researchers established an ecologically equivalent nonfeeder site, with similar plant communities, prescribed fire regimes, proximity to bodies of water, agronomic plantings, and infrastructure.¹

Among the 79 paired feeder and nonfeeder sites simultaneously sampled, researchers found more adult and nymphal ticks at nonfeeder sites than at feeder sites, likely the result of less vegetative cover. The feeder sites had significantly more host encounters and a 3 times more bare ground than the comparator sites which may itself reduce the number of ticks.¹

Although the researchers trapped fewer ticks at deer feeders, they indicate that the decrease may be due to ticks attaching firmly to deer and were not available for trapping. In other words, tick counts in traps and tick numbers on hosts may (or may not) correlate.¹

Previous studies have found a higher density of A. americanum nymphs infected with E. chaffeensis in areas with greater deer densities, suggesting increased risk of exposure,² but the present study found no difference in infection prevalence of ticks with Ehrlichia spp. or Rickettsia spp. between feeder and nonfeeder sites, despite the increased host visitation to feeders.

The use of supplemental feeding can result in large gatherings of animals, leading to increased potential for disease transmission. Feeding of deer and other wildlife has previously been implicated in the spread of various diseases, including bovine tuberculosis, raccoon roundworm, in addition to other endoparasites.

Yum-Chan is a 2022 PharmD candidate at the University of Connecticut School of Pharmacy

References

1. Huang MHJ, Demarais S, Strickland BK, et al. Supplemental feeding of deer reduces tick abundance in Mississippi, U.S.A. J Vector Ecol. 2022;47(1):29-37. doi:10.52707/1081-1710-47.1.29
2. Allan BF, Dutra HP, Goessling LS, et al. Invasive honeysuckle eradication reduces tick-borne disease risk by altering host dynamics. Proc Natl Acad Sci U S A. 2010;107(43):18523-18527. doi:10.1073/pnas.1008362107