Ticks
American dog tick, Dermacentor variabilis (Say);
brown dog tick, Rhipicephalus sanguineus (Latreille);
lone star tick, Amblyomma americanum (Linnaeus)
Ixodidae, METASTIGMATA


DESCRIPTION

Adult -- All ticks have 4 pairs of legs. American dog ticks have reddish-brown bodies with a white, mottled pattern on the dorsal shields and are about 4 to 5 mm in length. Brown dog ticks are uniformly reddish-brown and only 1.5 to 3 mm long. Engorged females can be 6 to 11 mm long.

Lone star ticks are light brown and vary from 3 to 4 mm in length. The female has a conspicuous, silvery white spot at the end of its dorsal shield. The male, on the other hand, has several crescent-shaped, white markings on the posterior portion of its dorsal shield.

Egg -- Eggs of American dog, brown dog, and lone star ticks are brown, shiny, oval, and about 0.5 mm long and 0.4 mm wide.

Larva -- About 0.5 to 1.0 mm long, tick larvae have only 3 pairs of legs. Those of the American dog tick are pale yellow with reddish-brown margins along their backs. Brown dog and lone star tick larvae are light brown.

Nymph -- Nymphs are about 1.5 to 2.5 mm long and have 4 pairs of legs. Lone star nymphs are reddish-brown and the other two species are yellowish-brown.


BIOLOGY

Distribution -- The American dog tick is especially abundant in eastern North America. Brown dog ticks are widely distributed throughout the world. The one star tick is found from Texas to Oklahoma, eastward to the Atlantic Coast and from Mexico to Central and South America. In North Carolina, the American dog tick is most common in the Piedmont region, whereas the lone star tick is generally restricted to the Coastal Plain area. The brown dog tick, however, is common throughout North Carolina.

Hosts -- American dog tick larvae and nymphs prefer to feed on the blood of rodents. Adults attack man, dogs, livestock, and wildlife such as raccoons and foxes. All stages of the brown dog tick prefer to feed on dogs; man and livestock are rarely attacked. All stages of the lone star tick attack man and other animals, such as cattle, sheep, horses, hogs, dogs, deer, and birds.

Damage -- The American dog tick is the primary vector of a disease organism that causes Rocky Mountain spotted fever in man in the southeastern U.S. Symptoms include headache, muscle and lower back pains, fever, chills, and a measles-like rash that starts on the wrists and ankles and spreads to the trunk of the body. These symptoms occur within 2 to 12 days following a tick bite. The disease can be fatal if medication is not administered properly. The organisms that cause Rocky Mountain spotted fever are retained by ticks even as they grow and develop. They can even be transmitted to the next generation of ticks by the female through the egg.

The feeding activity of the lone star tick often causes extreme nuisance. The salivary secretions injected by lone star and American dog tick females attached at the base of the skull in rare cases cause a condition known as "tick paralysis." Presumably the salivary toxins cause a neuromuscular block. Recovery is complete if the attached tick is removed before respiratory paralysis occurs. A severe infestation of brown dog ticks on pets may cause anemia.

Life History -- The lone star, brown and American dog ticks have similar life cycles. Adults of both sexes feed and mate on the host. A male may mate with several females before dying. After fertilization, a female drops off the host, deposits 3,000 to 5,000 eggs over a 3-week period and then dies. The eggs are deposited in protected areas such as in leaf litter, pine straw, or cracks and crevices in dog houses. A gelatinous material surrounds the eggs and prevents them from drying out.

In about a month, the eggs hatch into larvae which are often called seed ticks. They climb low vegetation or the walls of pest quarters to await a host and can live several months without finding one. Lone star and brown dog tick larvae rarely survie the winter. Nymphs and adults are the overwintering stages. Those successful in securing hosts feed for several days and then drop off to molt to the nymphal stage. Nymphs must also feed upon a host and may survive a year without a blood meal. Those that find a host feed for about a week, then drop off to molt to the adult stage. As with the immature stages, adult ticks await a host and can survive several years without one. The lone star, brown, and American dog ticks are referred to as 3-host ticks because each stage usually feeds on a separate host. The entire cycle may require three months to several years depending on the availability of hosts.


CONTROL

Refer to the Introduction for information on personal protection from ticks. Control of ticks over wide areas through the use of chemicals is impractical; however, satisfactory control on home grounds can often be obtained with some granular and liquid pesticide formulations. Because tick survival is dependent upon high relative humidity (over 85%), mowing and clearing away brush should help control American dog ticks and lone star ticks.