Risk factors for lyme disease in Chester County, Pennsylvania.
OBJECTIVE
To identify factors associated with increased or decreased risk of infection for Lyme disease in Chester County, Pennyslvania.


METHODS
The authors designed an unmatched case-control study involving 294 incident cases reported to the Chester County Health Department in 1998 and 449 controls selected by random digit dialing. All case and control participants were interviewed by telephone.


RESULTS
Age is a risk factor for Lyme disease for groups aged 10-19 years old and 50 years or older. Sex was not a risk factor. Incidence of Lyme disease in a rural setting was three times the incidence in an urban setting. Increased risk also was associated with living in single family homes, homes with yards or attached land, woods on the land, signs of tick hosts seen on the land, and homes within 100 feet of woodland. Gardening for more than four hours per week was also a risk factor, but most other outdoor activities were not. Twice as many participants took protective measures against tick bites before outdoor employment than those who merely ventured into the yard or land associated with the home. Only checking for ticks during outdoor activity and the use of repellents prior to outdoor activities outside the yard were unequivocally associated with a reduced risk of Lyme disease.


CONCLUSIONS
It is important to increase public awareness about the risk of acquiring Lyme disease from ticks in the immediate environment of the home.
Smith
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Section of Epidemiology and Public Health, University of Pennsylvania School of Veterinary Medicine, Kennett Square, Pennsylvania, USA. garys@vet.upenn.edu
Wileyto
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Hopkins
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Cherry
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Maher
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JP
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D015982:Bias; D016022:Case-Control Studies; D002648:Child; D004781:Environmental Exposure / Q000032:analysis / Q000706:statistics & numerical data*; D005191:Family Characteristics; D005260:Female; D015438:Health Behavior; D006801:Humans; D007302:Insect Repellents / Q000008:administration & dosage; D007407:Interviews as Topic; D008193:Lyme Disease / Q000453:epidemiology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D010414:Pennsylvania / Q000453:epidemiology; D011322:Primary Prevention; D011481:Protective Clothing / Q000706:statistics & numerical data; D018570:Risk Assessment; D012307:Risk Factors; D012423:Rural Health; D011795:Surveys and Questionnaires; D013689:Telephone
D007302:Insect Repellents