Biology of Ticks in SD
Biology of Ticks in SD
Mike Catangui, Ph.D. Associate Professor, South Dakota State University
Posted on April 19, 2000. Last updated on April 11, 2003.
About 17 species of ticks occur in South Dakota.
The American dog tick or
wood tick (Dermacentor variabilis) is the most commonly encountered tick species.
The deer tick or blacklegged tick (Ixodes scapularis)
is present but is quite rare.
A total of only 5 deer ticks have been collected so far from 5 eastern
counties. Deer
ticks that may have been picked up from surrounding states are not included in this
count.
Ticks are not insects. They are arachnids and are
more related to spiders, mites,
and scorpions than to insects. Adult and nymphal stages of ticks have 4 pairs of
legs
compared with the 3 pairs of legs in insects. However, the larval stage of ticks
(immediately following egg hatch) may be confused with insects since they too have
3 pairs of legs.
Ticks are obligate blood feeders. Their diet is made up
of blood and lymph of other
animals. Pets, livestock, rodents, birds, and humans are fed upon by ticks.
Human diseases that are known to be transmitted by
ticks in South Dakota are
tularemia,
Rocky Mountain Spotted Fever, and
Colorado tick fever. Local transmission
of Lyme disease by deer ticks has
been very rare with only one confirmed case from a
county close to the Iowa-Nebraska state lines.
Depending on the species, ticks can complete their life
cycles from 6 weeks to 2 years.
To complete their development, ticks usually feed on the blood of several host animals.
This is how disease-causing agents may be vectored by ticks from wild animals to
humans.
Ticks pierce the skin using their hypostome. It
is an elongated structure that contains
many recurved teeth. Once attached to the skin, ticks can be difficult to remove
while
feeding but will detach quickly when fully engorged with blood.
