Does reducing deer numbers reduce the risk of Lyme Disease and other tick-borne illnesses?
Many people hope that a deer reduction program will help to significantly reduce the risk of Lyme Disease in their area. However, scientific studies on the topic show mixed results, with most studies concluding that deer reduction does not produce a significant reduction in either tick abundance or Lyme Disease cases. Here are some examples of findings from studies relating deer populations to Lyme Disease incidence:
A study of the effects of reduced deer density on Lyme Disease incidence and tick abundance in New Jersey found that a 47% reduction of the deer population had no measurable effect on the number of ticks present or the incidence of Lyme Disease reported in the study area. The study concluded that while deer reduction programs may serve other community goals, they are not likely to serve as an effective means of controlling Lyme Disease (Jordan et al. 2007).
A study of the relationship between deer density, tick abundance, and Lyme Disease incidence in Groton, CT concluded that reduction of deer through hunting did reduce the incidence of Lyme Disease. They found that after hunting was initiated, the number and frequency of deer observations in the community were greatly reduced, as were resident-reported cases of Lyme disease. The number of resident-reported cases of Lyme disease per 100 households was strongly correlated to deer density in the community. Reducing deer density to 5.1 deer per square kilometer resulted in a 76% reduction in tick abundance and 80% reduction in resident-reported cases of Lyme disease in the community as compared with numbers reported before hunting took place (Kilpatrick et al., 2014).
A study of previously published data on deer, ticks, and Lyme Disease across the United States found that complete elimination of deer (such as from small island communities) did substantially impact the number of ticks present, reducing deer numbers has shown mixed results in changing tick densities. Overall, the study concluded that strong evidence linking deer control to reduced human Lyme disease risk is lacking, and felt there was insufficient evidence to recommend deer population reduction as a Lyme disease prevention measure (Kugeler et al., 2016).
A 2019 review of published research on Lyme Disease prevention strategies found no strong evidence supporting the effectiveness of deer culling for Lyme Disease reduction, and evidence for the effectiveness of applying pesticides to deer through the use of devices like 4-posters was inconclusive. The study found the most effective method for reducing Lyme Disease incidence in humans was educating the public on personal protection strategies (Richardson et al, 2019).
References:
Jordan, R.A., T.L. Schulze, and M.B. Jahn. 2007. Effects of Reduced Deer Density on the Abundance of Ixodes scapularis (Acari: Ixodidae) and Lyme Disease Incidence in a Northern New Jersey Endemic Area. Journal of Medical Entomology 44(5): 752-757. Accessed at https://academic.oup.com/jme/article/44/5/752/972557
Kilpatrick, H.J., A.M. Labonte, and K.C. Stafford, III. 2014. The Relationship Between Deer Density, Tick Abundance, and Human Cases of Lyme Disease in a Residential Community. Journal of Medical Entomology 51(4): 777-784. Accessed at https://academic.oup.com/jme/article/51/4/777/894869
Kugeler, K.J., R.A. Jordan, T.L. Schulze, K.S. Griffith, and P.S. Mead. 2016. Will Culling White-Tailed Deer Prevent Lyme Disease? Zoonoses Public Health 63(5): 337-345. Accessed at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4912954/
Richardson, M., C. Khouja, and K. Sutcliffe. 2019. Interventions to Prevent Lyme Disease in Humans: A Systematic Review. Preventative Medicine Reports 13: 16-22. Accessed at https://www.sciencedirect.com/science/article/pii/S2211335518302249