American Journal of Epidemiology

Copyright © 1996 by The Johns Hopkins University School of Hygiene and Public Health

All rights reserved

Vol. 143, No. 2

Printed in U.S.A.

Duration of Tick Bites in a Lyme Disease-endemic Area

Richard C. Falco,1'23 Durland Fish,2'4 and Joseph Piesman5

Regression equations, based on scutal index (body length/scutal width), were developed to determine the

duration of attachment for nymphal and adult female Ixodes scapularis ticks. Feeding times were calculated

for 444 nymphal and 300 female ticks submitted by bite victims between 1985 and 1989 in Westchester

County, New York, an area where Lyme disease is highly endemic. Nymphs were attached for a mean of 34.7 hours, with 26.8% removed after 48 hours, the critical time for transmission of Borrelia burgdorferi.Attachment times increased with victim age class (Kruskal-Wallis test, p < 0.05). Mean duration of attachment for female ticks (28.7 hours) was significantly less (Kruskal-Wallis test, p < 0.05) than that for nymphs, with 23.3% attached for more than 48 hours. The 0- to 9-year age class had the highest proportion (37.1%) of females attached for more than 48 hours. Nymphs remain attached to adult tick-bite victims longer than they remain attached to children. However, children have a high risk of acquiring Lyme disease because they receive more nymphal bites and also because they are less likely to have female ticks removed in time to prevent transmission. Am J Epidemiol 1996;143:187-92.

Lyme disease; tick-borne disease; ticks Lyme disease, caused by the spirochete Borrelia

burgdorferi is the most frequently reported vectorborne disease in the United States (1). The spirochete

is transmitted to people by the bite of infected ticks belonging to the Ixodes persulcatus group (2, 3). In the

Northeast, where almost 80 percent of the Lyme disease cases in the United States are reported (4), the

vector is Ixodes scapularis, formerly Ixodes dammini (5). Spirochete transmission occurs primarily in the

summer months through the bite of nymphal ticks, although adult females may also serve as vectors in the

spring and fall (2, 6).

Bites from /. scapularis ticks are common in Lyme disease-endemic areas, accounting for almost 80 per-

cent of all tick bites (7). In Westchester County, New York, where Lyme disease is endemic (8), it was

Received for publication October 12, 1994, and in final form October 31, 1995.

Abbreviations: ANOVA, analysis of variance; SE, standard error.

1

Vector Ecology Laboratory, Calder Ecology Center, Fordham

University, Armonk, NY.

2

Department of Community and Preventive Medicine, New York

Medical College, Valhalla, NY.

3

Bureau of Disease Control, Westchester County Department of

Health, Hawthorne, NY.

4

Present address: Department of Epidemiology and Public

Health, Yale University School of Medicine, New Haven, CT.

5

Division of Vector-Borne Infectious Diseases, National Center

for Infectious Diseases, Centers for Disease Control and Prevention,

Fort Collins, CO.

Reprint requests to Dr. Richard C. Falco, Vector Ecology Labo-

ratory, Calder Ecology Center, Fordham University, P. O. Box K,

Armonk, NY 10504.

FULL ARTICLE

http://aje.oxfordjournals.org/cgi/reprint/143/2/187.pdf