A clinician's guide to safe and effective tick removal

DR. HOWARD is a pediatric emergency medicine fellow at Alfred I. duPont Hospital for Children, Wilmington, Del.

DR. LOISELLE is assistant director of the division of emergency medicine at Alfred I. duPont Hospital for Children and associate professor of pediatrics at Jefferson Medical College, Philadelphia, Pa.

The authors have nothing to disclose in regard to affiliations with, or financial interests in, any organization that may have an interest in any part of this article.

Not all species of tick attach to humans and, of those that do, the likelihood that one will transmit a pathogen depends on its developmental stage and prevalence of infectious pathogens in a particular geographic area. Estimates are that the prevalence of the spirochete responsible for Lyme disease, Borrelia burgdorferi, in the nymphal stage of Ixodes scapularis, the deer tick, in endemic areas of the Northeast and Midwest, is 15% to 30%. (The responsible vector in the western states is I pacificus, a deer and cattle tick.) The likelihood of disease transmission from the bite of an infected tick is only 1% to 3%.¹ A patient who develops a tick-borne disease is unlikely to recall a tick bite-generally because a tick drops off its host after feeding.

Whether any pathogen is transmitted by the bite of a tick is determined by the location of that organism in the tick's gut and the duration of the tick's attachment to its host. A pathogen residing in the salivary glands of the tick will pass to its host more quickly and efficiently than one in the tick's lower gastrointestinal tract. The principal determinant of disease transmission, however, is the duration of the tick's attachment: The longer a tick is attached, the greater the likelihood that the pathogen will transmit to host.

Each pathogen requires a different duration of attachment.³ Transmission of B burgdorferi from an infected deer tick is unlikely with less than 24 hours of attachment, more likely after 48 hours than after 24, and highly likely after 72. Shorter periods of attachment may suffice for an infected tick to transmit Ehrlichia chaffeensis and E ewingii, the pathogens responsible for ehrlichiosis.¹ This research confirming the relationship between duration of attachment and the spread of infectious agents underscores the importance of timely tick removal.¹ The table provides a snapshot of common tick-borne diseases in the US.

The tick employs several appendages to achieve its tenacious grip on your patient host.^4,5 On each side of the hypostome-a rod-shaped structure through which the tick sucks blood from the host-are cheliceral digits that painlessly penetrate the host epithelium (see figure). Hundreds of barbs on the outer surface of the hypostome grip the skin like fishhooks as it enters the break in the epithelium. To strengthen its hold, the tick secretes a ring of cement around the cavity, fixing itself in place for a feast. It is while the tick feeds-a meal that can last several days or a week-that pathogens may be transferred to the host. Meal complete, the tick detaches from the patient's epidermis, leaving the cement behind. (Depth of attachment varies by tick; dog ticks, for example, attach superficially, whereas lone star ticks and Ixodes species attach more deeply within the epidermis.³)

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