Tick Bites, Tick-borne Illness
Conditions
Brief summary
The high risk of acquiring tick-borne diseases by outdoor workers is well documented. Workers most at risk include, foresters, park rangers, land surveyors and other outdoor workers have frequent exposure to tick-infested habitats. Many North Carolina state employees with outdoor occupations report multiple tick bites each year, which indicates that existing tick preventive strategies may be ineffective. The principal goal of this study is to assess whether the use of long-lasting permethrin impregnated uniforms can reduce the number of tick bites sustained by North Carolina outdoor workers.
Interventions
OTHERPermethrin Impregnated Uniforms
Uniforms treated with permethrin according to proprietary process used by Insect Shield, Inc.
Sponsors
North Carolina State University
University of North Carolina, Chapel Hill
Study design
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
PREVENTION
Masking
DOUBLE (Subject, Investigator)
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
* Being over 18 years of age * Employee of NC Division of Forest Resources, the NC Division of Parks and Recreation, NC Wildlife Resources Commission, or NC County and Local Parks and Recreation who work in Central and Eastern North Carolina * An average of 10 or more hours of outdoor work per week during tick season * Self-reported prior work-related tick bites
Exclusion criteria
* Pregnancy * Non-English speaking * Known allergy to insecticides
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Work Related Tick Bites | Weekly for two years | Tick bites are defined as ticks attached to or embedded in the skin |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Seroconversion Against a Tick-borne Illness | Upon enrollment, after the first year, and after the second year | We will define seroconversion as one in which there is a 4-fold change in Immunoglobulin G class antibody titer between sera at enrollment, sera obtained after one year and/or sera obtained at study's end or between acute and convalescent sera for participants developing an acute illness. The antigens that will be used in the serologic assays include Ehrlichia chaffeensis (which would also detect antibodies to E. ewingii and Anaplasma phagocytophilum) and Rickettsia rickettsii (which would also detect antibodies to other spotted fever group rickettsiae). |
Countries
United States
Participant flow
Participants by arm
| Arm | Count |
|---|---|
| Permethrin Impregnated Uniforms Uniforms (including pants, shorts, shirts, socks, and hats) treated with long-lasting permethrin.
Permethrin Impregnated Uniforms: Uniforms treated with permethrin according to proprietary process used by Insect Shield, Inc. | 67 |
| Placebo Uniforms sent to Insect Shield, washed and refolded (no permethrin applied). | 66 |
| Total | 133 |
Baseline characteristics
| Characteristic | Permethrin Impregnated Uniforms | Placebo | Total |
|---|---|---|---|
| Age, Continuous | 39.1 years STANDARD_DEVIATION 9.2 | 38.8 years STANDARD_DEVIATION 9.3 | 39.0 years STANDARD_DEVIATION 9.2 |
| Education, categorical Bachelor or graduate degree | 40 participants | 42 participants | 82 participants |
| Education, categorical High school or less | 5 participants | 10 participants | 15 participants |
| Education, categorical Some college | 20 participants | 14 participants | 34 participants |
| Previous diagnosis with tick-borne illness Anaplasmosis | 0 participants | 0 participants | 0 participants |
| Previous diagnosis with tick-borne illness Babesiosis | 0 participants | 0 participants | 0 participants |
| Previous diagnosis with tick-borne illness Ehrlichiosis | 2 participants | 3 participants | 5 participants |
| Previous diagnosis with tick-borne illness Lyme disease | 4 participants | 4 participants | 8 participants |
| Previous diagnosis with tick-borne illness Rocky Mountain spotted fever | 6 participants | 7 participants | 13 participants |
| Race/Ethnicity, Customized Black | 2 participants | 0 participants | 2 participants |
| Race/Ethnicity, Customized Other | 0 participants | 1 participants | 1 participants |
| Race/Ethnicity, Customized White | 56 participants | 58 participants | 114 participants |
| Sex/Gender, Customized Female | 14 participants | 11 participants | 25 participants |
| Sex/Gender, Customized Male | 52 participants | 55 participants | 107 participants |
| Tick bites in previous year, continuous | 19.3 tick bites STANDARD_DEVIATION 32 | 19.6 tick bites STANDARD_DEVIATION 39.3 | 19.4 tick bites STANDARD_DEVIATION 35.8 |
| Use of self-applied permethrin on clothing | 30 participants | 34 participants | 64 participants |
| Use of tick bite prevention measures Hat | 43 participants | 38 participants | 81 participants |
| Use of tick bite prevention measures Long pants | 62 participants | 62 participants | 124 participants |
| Use of tick bite prevention measures Long sleeves | 48 participants | 52 participants | 100 participants |
| Use of tick bite prevention measures Repellent on clothing | 38 participants | 35 participants | 73 participants |
| Use of tick bite prevention measures Repellent on skin | 22 participants | 22 participants | 44 participants |
| Use of tick bite prevention measures Tick checks after working outdoors | 58 participants | 60 participants | 118 participants |
| Use of tick bite prevention measures Tucked or taped pant legs | 5 participants | 7 participants | 12 participants |
| Work division, categorical NC Division of Parks and Recreation | 31 participants | 25 participants | 56 participants |
| Work division, categorical NC Forest service | 21 participants | 27 participants | 48 participants |
| Work division, categorical NC Local or County Parks and Recreation | 5 participants | 4 participants | 9 participants |
| Work division, categorical NC Wildlife Resources Commission | 9 participants | 10 participants | 19 participants |
| Years in current position, continuous | 7.9 years STANDARD_DEVIATION 6.7 | 8.2 years STANDARD_DEVIATION 6.8 | 8.0 years STANDARD_DEVIATION 6.7 |
Adverse events
| Event type | EG000 affected / at risk | EG001 affected / at risk |
|---|---|---|
| deaths Total, all-cause mortality | — / — | — / — |
| other Total, other adverse events | 0 / 67 | 2 / 66 |
| serious Total, serious adverse events | 0 / 67 | 0 / 66 |
Outcome results
Primary
Work Related Tick Bites
Tick bites are defined as ticks attached to or embedded in the skin
Time frame: Weekly for two years
| Arm | Measure | Value (NUMBER) |
|---|---|---|
| Permethrin Impregnated Uniforms | Work Related Tick Bites | 265 tick bites |
| Placebo | Work Related Tick Bites | 780 tick bites |
Comparison: Protective effectiveness (1 - the incidence rate ratio) and 95% CIs for comparing reported tick bites between the treatment and control groups were calculated using a GEE model with a Poisson distribution and log link, and included terms for treatment, year of follow-up, and the interaction of treatment and year of follow-up, with an offset variable for log outdoor work hours.p-value: 0.00495% CI: [0.288, 0.824]Poisson regression
Secondary
Seroconversion Against a Tick-borne Illness
We will define seroconversion as one in which there is a 4-fold change in Immunoglobulin G class antibody titer between sera at enrollment, sera obtained after one year and/or sera obtained at study's end or between acute and convalescent sera for participants developing an acute illness. The antigens that will be used in the serologic assays include Ehrlichia chaffeensis (which would also detect antibodies to E. ewingii and Anaplasma phagocytophilum) and Rickettsia rickettsii (which would also detect antibodies to other spotted fever group rickettsiae).
Time frame: Upon enrollment, after the first year, and after the second year