Risk factors for Lyme disease in a small rural community in northern California.
A 1-year prospective study of risk factors for seropositivity to and contraction of Lyme disease among members of a small rural community (population, approximately 150) was conducted in northwestern California in 1988-1989. The initial rate of seropositivity for Borrelia burgdorferi for 119 current or former residents ranged from 15 to 20% among three laboratories, with statistically significant interlaboratory agreement. Questionnaires were completed by 93 current residents at entry and 80 residents a year later to evaluate the association of serologic status with 20 categorical and 47 continuous variables. Seropositive subjects had resided in the study area about 2 years longer, were bitten by unspecified biting flies more often, and were less likely to have engaged in hiking than seronegative subjects. One of 59 seronegative subjects seroconverted a year later (annual incidence = 1.7%). The cumulative frequency of seropositivity for Lyme disease in the study population was > or = 24%. Of 83 subjects examined physically, 13 were diagnosed as having definite and 18 as having probable Lyme disease. The seropositivity rate was significantly higher (38.7%) among individuals with definite/probable Lyme disease than in asymptomatic subjects (13.5%). Subjects who were seronegative or free of Lyme disease reported nearly as many tick bites as subjects who were seropositive or had a diagnosis of the disease. Age, time spent outdoors in the fall multiplied by a clothing index, and woodcutting were significantly associated with Lyme disease in logistic regression analyses.
Lane
R S
RS
Department of Entomological Sciences, University of California-Berkeley 94720.
Manweiler
S A
SA
Stubbs
H A
HA
Lennette
E T
ET
Madigan
J E
JE
Lavoie
P E
PE
D000328:Adult; D000367:Age Factors; D000818:Animals; D001733:Bites and Stings / Q000150:complications / Q000453:epidemiology; D002140:California / Q000453:epidemiology; D003020:Clothing / Q000592:standards; D004175:Diptera; D005260:Female; D016468:Forestry; D006801:Humans; D015994:Incidence; D007299:Insect Bites and Stings / Q000150:complications / Q000453:epidemiology; D007899:Leisure Activities; D016015:Logistic Models; D008193:Lyme Disease / Q000097:blood / Q000453:epidemiology* / Q000209:etiology; D008297:Male; D015995:Prevalence; D011446:Prospective Studies; D012111:Residence Characteristics; D012307:Risk Factors; D012424:Rural Population; D012621:Seasons; D016036:Seroepidemiologic Studies; D011795:Surveys and Questionnaires; D013987:Ticks; D014937:Work