Comprehensive Description

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Comprehensive Description

The Lone Star Tick (Amblyomma americanum) was the first tick to be described in the United States, in 1754 (Childs and Paddock 2003). Female Lone Star Ticks have a conspicuous whitish spot (usually just one) on the back near the posterior end of the scutum (the scutum is the hard shield extending over roughly the anterior third of a female hard tick's dorsal surface and may be obscured in an engorged tick) (Cooley and Kohls 1944). Males lack this conspicuous white spot and, as in other male hard ticks, the scutum extends over most of the dorsal surface.

Because of its aggressive and mostly non-specific feeding habits and its high population densities, the Lone Star Tick is one of the most annoying and economically important ticks in the United States. Adults parasitize medium and large mammals (including cattle), and the larvae and nymphs feed on a wide variety of small to large mammals and ground-feeding birds (a large number of known hosts are listed in Cooley and Kohls 1944 and Bishopp and Trembley 1945), although availability of large mammalian hosts such as White-tailed Deer is likely essential to maintain large populations (Childs and Paddock 2003). Bishopp and Trembley (1945) counted around 4800 ticks, mainly Lone Star nymphs, on a single ear of a deer.

The Lone Star Tick is a three-host species, and is a general feeder in all its active stages (Bishopp and Trembley 1945). All three motile life stages will bite people (Cooley and Kohls 1944; Bishopp and Trembley 1945; Goddard and Varela-Stokes 2009), but it was not until the early 1990s that this tick was shown to be the principal vector for any human disease. Since the late 1980s, researchers have come to view this tick as more than just a nuisance (from a human perspective), but in fact an important vector of several diseases affecting humans (Childs and Paddock 2003). Although these diseases--human monocytic (or monocytotropic) ehrlichiosis (HME), Ehrlichia ewingii ehrlichiosis, and southern tick-associated rash illness (STARI)--were presumably present in the United States prior to their recognition, it is very likely that the prevalence of both these three diseases and the Lone Star Tick itself increased as a result of exploding populations of their keystone host, the White-tailed Deer, during the 20th century (Paddock and Yabsley 2007).


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© Shapiro, Leo

Source: EOL Rapid Response Team


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