Hunter risk sensitivity to ticks and tick-borne disease in Illinois

ABSTRACT

Tick-borne disease (TBD) is a public health issue, especially for hunters. Data were obtained from a mailed survey (n = 2,948, response rate = 59%) of Illinois adult resident hunters. Consistent with earlier work, hunter perception of vector-borne diseases could be categorized into an overall risk sensitivity index consisting of three clusters of respondents: no risk (40%), slight risk (45%), and moderate risk (15%). As predicted, individuals in the no-risk cluster consistently reported the lowest mean scores for the awareness of ticks, prior experience with ticks, perceived risks with ticks, and protective behavior indices. People in the moderate risk cluster reported the highest means on these indices. In contrast, means for those in the slight risk cluster were consistently between individuals in the no-risk and moderate risk clusters. Results underscore the need for identifying strategies to improve personal protective adoption measures by hunters with low-risk perception.

KEYWORDS:

• Hunters
• risk sensitivity
• tick-borne disease
• Ticks

Introduction

Reported tick-borne disease (TBD) cases in the United States rose substantially in recent decades (Kugeler et al., 2021). Reasons for this increase include greater tick abundance and range expansion (Raghavan et al., 2019; Sonenshine, 2018) stemming from climate change alterations to temperature and rainfall (Alkishe et al., 2021; Bacon et al., 2022), land-use changes (Gallagher et al., 2022), and increased host availability (Tsao et al., 2021). These vector-borne diseases pose a significant threat to public health (Schwartz et al., 2021).

Prior to 1990, Lyme disease and its vector in the Midwest, the blacklegged tick (Ixodes scapularis), were limited to Minnesota and northwestern Wisconsin (Callister et al., 1991). The endemic area soon spread into Illinois (Cortinas & Kitron, 2006) and surrounding states (Lingren et al., 2005). Illinois is now on the leading edge of tick and TBD expansion from both the north and south (Kopsco & Mather, 2022), and between 2000 and 2017 the state experienced a 10-fold increase in reported TBD human cases (Illinois Department of Public Health, 2021).

Lyme disease is the most common tick-borne disease within the state, with a 3-year average incidence of 1.7 confirmed cases per 100,000 people (Illinois Department of Public Health, 2021). Most cases, however, are concentrated in central and northern counties, with county-level incidence ranging from below 1 (e.g., Ford, Henry, and Schuyler counties) to more than 10 confirmed cases/100,000 people (e.g., Carroll, Jo Davies, and Putnam counties) (Illinois Department of Public Health, 2021). Lesser-known tick-borne infections like Rocky Mountain Spotted Fever, ehrlichiosis, and tick-borne viruses (e.g., Bourbon virus) are rarer (i.e., fewer counties with incidence greater than 2.6–5.0 cases per 100,000 people) and cases are concentrated in southern counties. These distributions reflect current tick vector habitat ranges within the state (Kopsco & Mather, 2022).

Tick-borne disease risk varies by tick species and habitat. The blacklegged tick (I. scapularis) is more commonly found in forested areas of central and northern Illinois counties (Bousman et al., 1990; Callister et al., 1991; Gilliam et al., 2020; Illinois Department of Public Health, 2021). The lone star tick (Amblyomma americanum), which vectors ehrlichia species, spotted fever group rickettsiae bacteria, Bourbon virus, and can trigger alpha-gal syndrome (AGS), is located predominantly in the southern tier of the state (Gilliam et al., 2020; Illinois Department of Public Health 2021). The American dog tick (Dermacentor variabilis) is ubiquitous throughout the state, but cases of Rocky Mountain Spotted fever tend to be concentrated in the southern counties (Illinois Department of Public Health, 2021). Awareness of the lesser-known tick-borne illnesses is important regardless of prevalence due to the severity of these infections. Untreated, Rocky Mountain Spotted Fever has an estimated case fatality rate of 5–10%, and infection with Ehrlichia chaffensis has a 1% case fatality rate (Biggs et al., 2016).

Research suggests that people who spend considerable time outdoors, like hunters, have a higher risk of exposure to tick bites and infection (Sgroi et al., 2021) due to environmental and tick host exposure (Kmetiuk et al., 2019). Effective preventative measures for this group depend on hunters’ perceived risk (Eisen & Dolan, 2016). Evidence suggests Midwesterners tend to use repellents more often than those living in other regions of the country (Bron et al., 2020). Still, other data document that deer hunters are specifically less likely to use repellents to evade detection by deer (Gunter et al., 2020). The use of personal protective measures against ticks is highly dependent on the perceived risk of bites and potential infection if bitten. Perceived risk is the extent individuals believe they could be exposed to a specific hazard (e.g., wildlife disease) (Vaske & Miller, 2019), and involve subjective evaluations of the potential impacts of a given disease (Needham et al., 2017). Specific concerns about a disease sometimes do not influence perceived risks because some individuals are predisposed to rate all risks similarly (Sjöberg, 2002). This phenomenon reflects a general risk sensitivity (Miller & Shelby, 2009; Needham et al., 2017; Vaske & Miller, 2019).

Risk sensitivity of hunters has been examined in the context of wildlife-maintained pathogens, like chronic wasting disease (CWD), a transmissible spongiform encephalopathy (TSE) in wild cervids that was first documented in Illinois in November 2002 (Mateus-Pinilla et al., 2013; Miller, 2004). Miller and Shelby (2009) measured risk perceptions among Illinois hunters for CWD, vector-borne diseases (e.g., Lyme disease, West Nile virus (WNV)), and food-borne illnesses (e.g., Salmonella, E. coli) of food safety concerns when handling and consuming game meat. Cluster analysis of these risks revealed no (24%), slight (57%), and moderate (19%) risk groups, and these risk perceptions were associated with differences in hunting behavior. Needham et al. (2017) replicated the Miller and Shelby (2009) study, and cluster analysis also grouped hunters into no (42%), slight (44%), and moderate (14%) risk groups based on perceptions of health risks from CWD. Hunters who perceived higher health risks from CWD (i.e., moderate risk), however, perceived greater risks associated with CWD to other humans, CWD to wildlife, hunting to personal health, other diseases to health, and the future of hunting. These findings illustrated that hunters who perceived higher risks from CWD were predisposed to rate all other risks as large, but whether these risk perception groups can be applied to other potential hunting risks, like TBDs, is currently unknown. We sought to examine relationships between hunters’ general risk sensitivity to wildlife diseases and their awareness of ticks, prior experience with ticks, perceived risks with ticks, and tick bite protective behaviors. Further, we examined whether Illinois hunters can be classified into similar risk perceptions clusters regarding ticks and tick-borne diseases as hunters have been with other diseases (Miller & Shelby, 2009; Needham et al., 2017; Vaske & Miller, 2019). We examined the following hypotheses:

H₁:

Hunters’ perceived risks associated with specific TSEs, food-borne illnesses, and vector-borne diseases can be grouped into homogeneous and meaningful subgroups that reflect general risk sensitivity.

As general risk sensitivity increases:

H₂:

awareness of tick-borne illnesses increases.

H₃:

personal experience with tick-borne illnesses increases.

H₄:

perceived risks associated with tick-borne illnesses increases.

H₅:

protective behaviors related to tick-borne illnesses increases.

Methods

A random sample of 5,000 Illinois adult resident hunters was selected from the Illinois Department of Natural Resources hunting license database. Hunters were mailed a self-administered, 8-page questionnaire, cover letter, and postage-paid return envelope (i.e., survey packet) on May 27, 2021. A thank you/reminder postcard was mailed on June 18, 2021. On July 6, 2021, a second survey packet was mailed to non-respondents, and a second thank you/reminder postcard on July 22, 2021. A final survey packet was mailed August 10, 2021.

The questionnaire contained items related to four domains: eight items investigated awareness of tick-borne illnesses, five statements examined personal experience with ticks (Yes or No), perceived risk of tick-borne diseases compared with five other illnesses/diseases (unipolar 4-point scale), and self-reported preventative behaviors (5-point bipolar scale). Following previous research (Miller & Shelby, 2009; Needham et al., 2017; Vaske & Miller, 2019), K-means cluster analysis was performed for two, three, four, and five cluster solutions using the disease/illness comparisons. To validate solutions, data were randomly sorted, and a cluster analysis was conducted after each of three random sorts. One-way analysis of variance was used to examine hypotheses 2 through 5; eta was the effect size indicator. Data were cleaned and analyzed using SPSS 28.0 (SPSS Inc., 2021).

Results

Out of 5,000 surveys mailed, 2,948 responses were received (59%). Respondents were predominantly male (92%), white (92%), and had a mean age of 55 years, reflective of the overall Illinois hunting population (Walberg et al., 2021). Illinois hunters (N = 249,554) spent a total of 5,445,320 days afield hunting species (e.g., white-tailed deer, turkeys, small game, and furbearers) in habitats where, and during seasons when ticks may be present, for an average of 21.8 days/hunter.

The three-group cluster solution provided the best fit for the data, supporting hypothesis 1 that hunters’ perceived risks associated with specific TSEs, food-borne illnesses, and vector-borne diseases can be grouped into homogeneous and meaningful subgroups that reflect general risk sensitivity. Individual items for each of the three clusters indicated that those in the “no risk” cluster (n = 867, 40%) consistently reported the lowest means (M = 1.0), whereas those in the “moderate risk” cluster (n = 284, 15%) consistently had the highest means (M = 3.0) (Table 1). Means for respondents in “slight risk” cluster (n = 752, 45%) were between means for the other two clusters (M = 2.0).

Table 1. Cluster analysis of perceived risks associated with diseases and viruses.

	Overall Disease Risk Sensitivity^a
How much risk do you feel from each of the following?	Cluster 1 No Risk	Cluster 2 Slight Risk	Cluster 3 Moderate Risk
Contracting Lyme Disease	1	2	3
Contracting Rocky Mountain Spotted Fever	1	2	3
Becoming ill from Chronic Wasting Disease	1	2	3
Becoming ill from Salmonella food poisoning	1	2	3
Becoming ill from E. coli food poisoning	1	2	3
Contracting West Nile Virus	1^a	2	3
Cluster sample size	867	752	284
Percent of sample	40%	45%	15%

^aCell entries are means rounded to whole numbers to highlight the pattern.

More than 60% of respondents had heard of Lyme disease (91%) and Rocky Mountain spotted fever (65%) (Table 2). Only 24% of hunters were aware that tick bites could cause a red meat allergy. Of the remaining six items less than 10% had heard of any of the other illnesses (e.g., Tularemia, 8%; Borrelia infection, 7%; Bourbon virus, 3%). The additive scale of these knowledge items had a mean of 1.9 and a standard deviation of 1.2. Many respondents reported personal experiences with ticks (Table 2). Over 80% of the hunters had picked a live tick from their clothes or body after hunting and 77% had been bitten by a tick. The remaining three experience items were each less than 50% (e.g., 45% knew someone who had been diagnosed with a tick-borne illness). The mean for the additive index was 2.4, and the standard deviation was 1.2.

Table 2. Awareness of and experience with ticks.

	Variable		Index
	Number	Percent Yes	M	SD
Awareness^a Have you heard of any of the following tick-borne illnesses
Lyme disease	1846	91
Rocky Mountain spotted fever	1308	65
Red meat allergy	717	24
Tularemia	169	8
Borrelia infection	136	7
Ehrlichiosis	103	5
Anaplasmosis	88	4
Babesiosis	71	4
Bourbon virus	60	3
Awareness Index			2.17	1.35
Personal Experience^a
Have you ever picked a live tick off of your clothes or body after hunting	1669	82
Have you ever been bitten by a tick (i.e. had it attached to your body)	1560	77
Do you personally know anyone diagnosed with a tick-borne illness	903	45
Have you ever picked a live tick off of deer you have harvested	707	35
Have you ever submitted a tick to be tested after finding it when hunting	37	2
Experience Index			2.40	1.18

^aVariables coded as 0 = No, 1 = Yes. Index equals of the sum of the individual variables.

Perceived risks associated with ticks were assessed with three statements (Table 3). Each of these items were measured on four-point unipolar scales (1 = no risk, 4 = high risk). Means ranged from 2.2 (Getting bitten by a tick on your property, SD = .91) to 2.4 (Getting bitten by a tick while hunting, SD = .84). The Cronbach’s alpha reliability coefficient for this index was .79; deleting any of the items did not improve the reliability. The mean for the three-item scale was 2.2 (SD = .71).

Table 3. Reliability analyses for perceived risks associated with ticks and protective behaviors.

	M	SD	Item total correlation	Alpha if item deleted	Cronbach alpha
Perceived Risks Associated with Ticks^a					.787
Getting bitten by a tick while hunting	2.36	0.843	.711	.616
Getting bitten by a tick on your property	2.16	0.908	.612	.733
Contacting a disease from a tick bite	2.22	0.767	.569	.771
Perceived Risk Index	2.25	0.705
Protective Behaviors^b					.789
Tuck pants into boots/socks	2.95	1.381	.586	.747
Wear long-sleeved shirts	3.55	1.135	.570	.751
Tape pants legs closed	1.62	1.048	.397	.788
Wear DEET or other insect repellents	3.50	1.205	.456	.777
Remove clothing after returning indoors	3.17	1.332	.649	.729
Showering immediately when you get home	3.60	1.196	.590	.746
Protective Behavior Index	3.09	0.861

^aVariables were coded on a five-point scale from 1 (no risk) to 4 (high risk).

^bVariables were coded on a five-point scale from 1 (never) to 5 (always).

An index of protective behaviors was constructed from six items, each measured on 5-point unipolar scales (1 = never to 5 = always) (Table 3). Means ranged from 1.6 (taped pants legs closed, SD = 1.1) to 3.6 (showering immediately after returning home, SD = 1.2). The reliability coefficient was .79; removing any of the items did not improve the Cronbach’s alpha. The mean for the index was 3.1 (SD = .86).

Consistent with hypotheses 2–5, individuals in the no risk cluster reported the lowest mean scores for the awareness of ticks, prior experience with ticks, perceived risks with ticks, and protective behavior indices (Table 4). People in the moderate risk cluster reported highest means on these indices, whereas means for those in the slight risk cluster were between individuals on the no risk and moderate risk clusters. Each of the overall F-values were statistically significant (p < .001), as was each pair-wise comparison of means (indicated by different superscripts in Table 4). Effect sizes (eta) were minimal for awareness, experiences, and protective behaviors (i.e., .11 to .15), but substantial for perceived risk (Eta = .48).

Table 4. Perceptions and behaviors associated with ticks by overall disease risk sensitivity.

	Overall Disease Risk Sensitivity^a
Index	No Risk M	Slight Risk M	Moderate Risk M	F-value	p-value	Eta
Awareness of ticks	2.01^a	2.21^b	2.50 ^c	19.83	<.001	.122
Experience with ticks	2.34^a	2.45^b	2.75 ^c	13.51	<.001	.120
Perceived risks with ticks	1.93^a	2.26^b	2.96 ^c	290.60	<.001	.484
Protective behaviors	2.98^a	3.08^b	3.37 ^c	22.94	<.001	.154

^aMeans with different superscripts differ statistically at p < .05 based on LSD tests.

Discussion

Consistent with previous research (Miller & Shelby, 2009; Needham et al., 2017; Vaske & Miller, 2019), specific TSEs, food-borne diseases, and vector-borne diseases could be categorized into an overall risk sensitivity index consisting of three clusters: “no risk,” “slight risk,” and “moderate risk.” The risk sensitivity index was statistically related to awareness of ticks, prior experience with ticks, perceived risks with ticks, and protective behavior indices in the predicted directions. These findings supported each of the five hypotheses.

Although hunters reported high awareness for Lyme disease, many of the other tick-borne diseases present and causing increasing incidence within Illinois were far less known. Of note was the lack of hunter knowledge regarding AGS from tick bites. Commonly called a “red meat allergy,” AGS is the development of specific IgE antibodies to a carbohydrate (galactose-α-1–3-galactose) on the surface of mammalian muscle tissue, that is known to be triggered by tick bites (Commins et al., 2011). Symptoms range from mild skin and gastrointestinal disturbances to full anaphylaxis, occur typically between two and six hours after consuming mammalian meat or dairy products, and sensitivity may take years to subside, if at all (Binder et al., 2022). Bites from lone star ticks are most frequently associated with the development of the allergy (Mitchell et al., 2020), but other species like the blacklegged tick have also been implicated (Crispell et al., 2019). Mitchell et al. (2020) documented an increase in the presence of IgE antibodies to alpha-gal in outdoor workers who were exposed to tick bites, particularly from lone star ticks, making knowledge of this potentially deadly condition of critical importance to hunters.

Presently, the lack of broader awareness of AGS among hunters in Illinois can mostly likely be attributed to a combination of underdiagnosis and underreporting, and delayed onset of symptoms. Within Illinois, a survey of healthcare providers found that only 32% of physicians knew that tick bites are a main cause of AGS, and fewer than 18% knew about diagnostic IgE testing (Carson et al., 2022). Nationwide, Carpenter et al. (2023) found that 42% healthcare providers were not aware of the condition at all, and 35% reported a lack of confidence in diagnosing or treating AGS patients. A recent systematic review found that most cases of AGS (74%) present with skin reactions, which could either be overlooked or simply not attributed to a mammalian meat allergy (Young et al., 2021).

Sensitization also typically occurs over time with an increasing number of tick bites (Young et al., 2021), so a direct link between tick exposure and AGS can be challenging to pinpoint.

Research into knowledge, attitudes, and practices regarding ticks and TBD has previously established that increased perception of risk is strongly associated with increased usage of protective behaviors, including tick checks, use of skin and clothing repellents, and property-based control methods (Beck et al., 2022; Hassett et al., 2022). Those who knew of multiple prevention methods were also more likely to perform tick checks (Hassett et al., 2022), as were people who personally knew someone who was diagnosed with a TBD (Beck et al., 2022). Results from our study supported these prior findings; hunters in the slight and moderate risk perception category were also significantly associated with performing more protective measures like wearing DEET repellent, wearing protective clothing, and showering immediately upon arriving home from the field. However, it is important to note that the effect sizes for these differences were minimal.

The strongest effect size was seen between risk perception of ticks and overall risk sensitivity. Given prior studies that have demonstrated that increased knowledge positively correlates with tick risk perception (Beck et al., 2022; Crist et al., 2022; Hassett et al., 2022), education interventions might be successful in increasing awareness of tick hazards and thereby usage of personal protective strategies among hunters, particularly those with low risk sensitivity. However, these strategies must be targeted at overcoming the specific barriers that hunters perceive regarding personal protection methods, for example, the odor of DEET making them conspicuous to game they are hunting. Hunter education courses are offered in all 50 states, and generally overseen by state fish and wildlife agencies (Quartuch et al., 2021). This state-level structure provides an easily accessible setting to provide additional educational messaging and information on best practices for how hunters can protect themselves against tick bites and TBDs while in the field in ways that are compatible with hunting practice. Since these courses are taught by hunters and other trusted individuals within the outdoor sporting community, information on personal protection may be more readily received by those who might be less inclined to trust standard public health messaging, a common occurrence seen in rural communities (Lister & Joudrey, 2023).

Our findings highlight the need to identify strategies to improve personal protective adoption measures by hunters with low-risk perception. Vaske and Miller (2019) reported less risk sensitivity toward vector-borne illness, but slightly increased sensitivity toward food-borne illness over time in the Illinois deer hunter population. Given the lack of knowledge regarding the connection between tick bites and AGS, future research should re-examine risk perception categories between hunters who have and have not received education on tick-associated meat allergy. Examining the change in risk perception toward tick-borne diseases over time will also help researchers and those involved in hunter education to appropriately adjust TBD prevention guidance to this population. Future work should further quantify the specific risk that ticks in Illinois pose to hunters. This investigation can include passive tick collections from those afield to better describe the differential tick encounters experienced based on game season and location in conjunction with preventative actions. From these more detailed surveys, next steps should include developing education interventions that focus on protective methods that are both effective and easily adoptable by various types of hunters.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Additional information

Funding

Funding for this project was provided by U.S. Fish and Wildlife Service Federal Aid in Wildlife Restoration grant W-112-R-29. The University of Illinois Institutional Review Board approved the survey [#10236].