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Organisms Borne by Ticks and Other Vectors 247

Amblyomma americanum: The lone star tick occurs their pets. Nymphs are most abundant from late spring
across the southeastern and south-central United States. into early summer. After the development of the nymphs
It is most common as one travels further south but is into adults, they feed primarily on deer, as deer are
found in significant numbers in mostly moist wood- very important to the reproductive success and spread
lands. Adult females are characterized by a pearly white of the black-legged tick. Adults are found in late summer
spot at the tip of the scutum and by long mouthparts. into fall and again in early spring. A female lays about
A wide range of animal hosts serve as a source of blood, 3000 eggs before she dies.
including ground-dwelling birds, small mammals, and Adult western black-legged ticks are rarely found on
large mammals such as deer, livestock, and pets. All de- humans, but they do feed on dogs and cats (Figure 11-23).
velopmental stages of the lone star tick feed readily on Nymphs appear to be the main vectors of Lyme disease
humans. Larvae, which are sometimes referred to as to humans and pets. Nymphs are approximately the size
either “seed ticks” or “turkey ticks,” most often appear of a poppy seed and are therefore almost never seen by
in the spring and again in the fall. The nymphs of this a human. For this reason, people entering areas in which
species over-winter and are active from April into July. Lyme disease is transmitted are strongly encouraged to
Adults also over-winter and are active from late March wear proper clothing and to use a repellent. In addition to
into June. A female can produce up to 8000 eggs before Lyme disease, the black-legged tick is a vector of human
she dies. anaplasmosis and babesiosis. More information on Ixodes
The lone star tick is the second most common tick scapularis is available from Purdue Extension publication
found on humans especially in most of the southern E-244-W Lyme disease.
states. The long and barbed hypostome of female adults
inflicts a deep feeding wound and engorging females
have been associated with tick paralysis. This species is
a vector of spotted fever and the two recently recognized
diseases of ehrlichiosis and Southern tick-associated
rash illness (STARI).

Ixodes scapularis: The black-legged tick occurs
throughout the eastern United States, and can be locally
abundant in moist woodlands with thick leaf litter.
Adults are significantly smaller than Amblyomma and
Dermacentor ticks and have a characteristic uniform
deep mahogany color. Female black-legged ticks are
somewhat tear drop–shaped and have longer mouth-
parts than other species. Males are smaller than females
and in comparison have shorter mouthparts. The areas
in which these ticks range have tended to increase since
the late 1980s but appears to be much more abundant
in the more northern sections of the United States than
is the lone star tick. Source: Centers for Disease Control and Prevention (CDC)
The black-legged tick has a very wide host range.
Specimens have been collected from more than 100 spe-
cies of birds, mammals, and lizards, with roughly half
found on birds and about 10 percent found on lizards.
Black-legged tick larvae feed primarily on white-footed
mice and are most abundant from July into September.
Nymphs feed primarily on a variety of small, ground- FIGURE 11-23 Dorsal view of adult female western
dwelling vertebrates, but are also found on humans and blacklegged tick, Ixodes pacificus