Comparison of self-assessment and scutal index for the duration of Ixodes ricinus tick attachment.
Experimental studies have shown that the efficacy of transmission of B. burgdorferi sensu lato from an infected tick to an experimental animal is significantly associated with the duration of tick attachment. Scutal index is the ratio between body length and scutum width and was found to be an objective indicator of the duration of Ixodes scapularis tick attachment, but no data for I. ricinus have been published. In this preliminary report on 30 volunteers with an attached I. ricinus tick (21 had an adult female tick and 9 a nymph), none developed any sign of Lyme borreliosis but we were able to demonstrate two asymptomatic seroconversions in a six-week follow-up period. Twenty-six (87%) volunteers claimed that they were able to determine the approximate duration of tick attachment; participants with attached adult female ticks estimated the duration of attachment to be 30 (2-90) hours, while those with attached nymphs reported 48 (18-90) hours (p = 0.681). Scutal indices were 3.2 (2-5) for nymphs and 3.2 (1-5) for adult ticks, indicating 60- and 48-hour attachment, respectively. According to the volunteers' assessment and scutal index findings, approximately 80% and 45% of adult female ticks were removed within 48 hours after the tick bite (p = 0.032), respectively, while the corresponding values for nymphs were 85% and 17% (p = 0.053). Our findings were limited by low numbers of volunteers and by the lack of experimental data on the value of the scutal index for estimation of the duration of I. ricinus tick attachment.
Logar
Mateja
M
Department of Infectious Diseases, University Medical Centre, Ljubljana, Slovenia. mateja.logar@mf.uni-lj.si
Ruzić-Sabljić
Eva
E
Strle
Franc
F
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D001179:Arthropod Vectors; D001317:Austria; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D018884:Ixodes / Q000254:growth & development* / Q000382:microbiology; D008018:Life Cycle Stages / Q000502:physiology*; D008193:Lyme Disease / Q000175:diagnosis / Q000635:transmission*; D008297:Male; D008487:Medical History Taking; D008875:Middle Aged; D015203:Reproducibility of Results; D013997:Time Factors