Nymphs. Nymphs are ready to feed in May and
the west, their dogs contracted RMSF from the wood
tick and transmitted it to the American dog tick. The
June. The body of the nymph is tan with black legs
American dog tick then became the principal vector of
and a black shield (scutum) near its front. Nymphs
the disease and has carried it around the world.
climb vegetation and attach to passing animals such as
The Lone Star tick, Amblyomma americanum,
dogs, cats, horses, cattle, raccoons, opossums,
migrating birds and humans as well as mice.
ranges in the southeastern quarter of the United States
Nymphs live in what is classically called the
from Texas to northern Missouri and east to New
Jersey. The lone star tick can transmit Rocky
"white-footed mouse habitat," where larvae fed the
Mountain Spotted fever, but it is not as important an
previous late summer. This habitat is best described as
RMSF vector as the previous two species of
woodlands: bushy, low shrub woodland edge regions
and grassy areas that border woodlands. This is also
deer habitat. The mice travel in trails and nest almost
anywhere they can find a sheltered depression.
Nymphal tick activity coincides with human outdoor
activity, and peak human infection symptoms occur in
early July. Ninety percent of the human Lyme disease
cases are the result of nymphal tick feeding. The
remainder is due to adult activity. Nymphs usually
molt into the adult stage in late summer; they
sometimes overwinter and molt in the spring.
Adults. The body of the adult female is brick red
with black legs; she has a black shield (scutum) in the
front. The male is entirely dark and smaller than the
Adults feed on deer which are unaffected by the
Lyme disease. Where these deer move while hosts of
egg-laying females determines the distribution pattern
of the next generation. Adults feed in late fall or
spring. Deer ticks also bite on warm days in winter.
Hosts of the western blacklegged tick are dogs, cats,
sheep, horses, cattle, and deer.
AMERICAN DOG TICK
The American dog tick larvae and nymphs attack
small mammals and the adults attack larger mammals
-- dogs, horses, and humans. Larval and nymphal
stages prefer small rodents especially Microtus, the
short tailed voles, called meadow mice.
The deer tick is unlike the larger Lone Star Tick,
American Dog Tick, and Rocky Mountain Spotted
Fever Tick (see below). Larvae are no larger than the
period at the end of this sentence. Nymphs are close in
size to the adult -- a little less than 1/6 inch, or the
size of the head of a pin. Adult deer ticks are the size
of a sesame seed. Deer ticks have a two-year life cycle
and utilize three different hosts.
Eggs and Larvae. Eggs of the deer tick are laid
in the spring by overwintering females. Tiny larvae
hatch and feed on white-footed mice and other mice in
the late summer. Larvae can feed on humans but will
not transmit Lyme disease. Larvae overwinter, and in
the following spring, they molt into the nymphal stage.
Module Two, Chapter 4, Pg 5