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Ticks are blood-feeding external parasites (Figure 99-1). Ticks are a significant infectious disease problem in the United States as well as worldwide. They have been implicated as vectors in the transmission of many diseases including Lyme disease, ehrlichiosis, babesiosis, Rocky Mountain spotted fever, tularemia, tick paralysis, and tick-borne relapsing fever. Disease transmission is postulated to occur when stomach contents and saliva from the tick are introduced into the host during the blood-feeding process. There is significance in how long a tick has been attached and how quickly a feeding tick can be removed to the transmission of tick-borne diseases. Early removal is felt to limit the transmission of disease. For example, current entomological thinking suggests that the tick must be attached for at least 24 hours in order to transmit B. burgdorferi, the spirochete responsible for Lyme disease.1

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There are two main families of ticks.2 Hard body ticks belong to the Ixodidae family. Soft body ticks belong to the Argasidae family. Hard body ticks are responsible for the transmission of the majority of human diseases and will be the focus of this chapter. Hard ticks pass through four life cycle stages from birth (egg, larva, nymph, and adult). They require a blood meal in order to progress into the next stage of their development.

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The bite of a tick is painless and often goes unnoticed unless the tick is found attached to the skin. Ticks are often encountered in the late spring, summer, and early fall. Ticks are more prevalent in rural and wooded areas. They like to feed in dark (covered) and moist areas of the body such as the axilla, groin, or scalp.

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Ticks have specialized mouthparts that make their removal difficult (Figure 99-2).2 They screw their mouthparts into the skin in a clockwise direction. Mouthparts include the palps, the chelicerae, and the hypostome. The chelicerae are used to cut through the host's epidermis and allow passage of the tick's hypostome, through which the feeding takes place. Ticks attach themselves to their host by inserting the rod-like hypostome into the skin. The hypostome has many backward pointing sharp barb-like projections that prevent it from being pulled out. Additionally, some ticks secrete a cement-like material around the hypostome to secure its attachment to the host while it feeds. The longer the tick is attached, the more difficult it becomes to remove it intact. The tick releases its mouthparts from the host after the meal is complete. It can take anywhere from hours to days for an adult tick to finish its blood meal and detach from its host.4

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Figure 99-2.
Graphic Jump Location

The specialized mouthparts of the tick.

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Any tick found attached to ...

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