Although ticks are commonly thought of as insects, they are actually arachnids like scorpions, spiders and mites. All members of this group have four pairs of legs as adults and have no antennae. Adult insects have three pairs of legs and one pair of antennae. Ticks are among the most efficient carriers of disease because they attach firmly when sucking blood, feed slowly and may go unnoticed for a considerable time while feeding. Ticks take several days to complete feeding.
Ticks have four life stages: egg, six-legged larva, eight-legged nymph and adult. After the egg hatches, the tiny larva (sometimes called a seed tick) feeds on an appropriate host. The larva then develops (molts) into the larger nymph. The nymph feeds on a host and then molts into an even larger adult. Both male and female adults find and feed on a host, then the females lay eggs sometime after feeding.
Ticks wait for host animals from the tips of grasses and shrubs (not from trees). When brushed by a moving animal or person, they quickly let go of the vegetation and climb onto the host. Ticks can only crawl; they cannot fly or jump. Ticks found on the scalp have usually crawled there from lower parts of the body. Some species of ticks will crawl several feet toward a host. Ticks can be active on winter days when the ground temperatures are about 45 o Fahrenheit.
There are two groups of ticks, sometimes called the hard ticks and soft ticks. Hard ticks, like the common dog tick, have a hard shield just behind the mouthparts (sometimes incorrectly called the head); unfed hard ticks are shaped like a flat seed. Soft ticks do not have the hard shield and they are shaped like a large raisin. Soft ticks prefer to feed on birds or bats and are seldom encountered unless these animals are nesting or roosting in an occupied building.
Although at least 15 species of ticks occur in Illinois, only a few of these ticks are likely to be encountered by people: American dog tick, lone star tick, blacklegged (deer) tick, brown dog tick and winter tick.
American Dog Tick (Dermacentor variabilis )
One of the most frequently encountered ticks is the American dog tick, also sometimes known as the wood tick. The larvae and nymphs feed on small warm-blooded animals such as mice and birds. The adult American dog tick will feed on humans and medium to large mammals such as raccoons and dogs.
Unfed males and females are reddish-brown and about 3/16-inch long. Females have a large silver-colored spot behind the head and will become ½-inch long after feeding or about the size of a small grape. Males have fine silver lines on the back and do not get much larger after feeding. Males are sometimes mistaken for other species of ticks because they appear so different from the female.
In Illinois, the adults are most active in April, May and June. By September, the adults are inactive and are rarely observed. The American dog tick can transmit Rocky Mountain spotted fever. tularemia and possibly ehrlichiosis to humans.
Lone Star Tick (Amblyomma americanum )
The lone star tick is primarily found in the southern half of Illinois, although it can occasionally be found further north. Larvae, nymphs and adults will feed on a variety of warm-blooded hosts, including people. The larva is very tiny, only a little larger than the period at the end of this sentence. The nymph, the most common stage found on people, is about pinhead-sized. Adults are about 1/8-inch long and brown. The adult female has a white spot in the middle of her back. Because they are so similar in size, the lone star tick is sometimes misidentified by laypersons as the blacklegged / deer tick (see below).
The lone star tick is most active from April through the end of July. Although it can transmit Rocky Mountain spotted fever, the lone star tick is not as likely to transmit the disease as the American dog tick. This tick also may transmit tularemia and ehrlichiosis to humans. The lone star tick is not believed to transmit the bacteria that causes Lyme disease (Borrelia burgdorferi ). but may be associated with a related bacteria species that has not been completely identified.
Blacklegged Tick, also known as the Deer Tick (Ixodes scapularis )
All three active stages of the blacklegged / deer tick will feed on a variety of hosts including people. After the eggs hatch in the spring, the very tiny larvae feed primarily on white-footed mice or other small mammals. The following spring, the larvae molt into pinhead-sized, brown nymphs that will feed on mice, larger warm-blooded animals and people. In the fall, they molt into adults that feed primarily on deer, with the females laying eggs the following spring. Adults are reddish-brown and about 1/8-inch long (or about one-half the size of the more familiar female American dog tick).
These ticks are found in wooded areas along trails. The larvae and nymphs are active in the spring and early summer; adults may be active in both the spring and fall. The blacklegged / deer tick can transmit Lyme disease, babesiosis and possibly ehrlichiosis to humans.
The deer tick has been found sporadically in many Illinois counties. However, in recent years it has been common only in limited areas, mostly in northern Illinois (Geographic distribution by county). Additionally, Illinois residents may encounter the deer tick during trips to Michigan, Minnesota, Wisconsin or the northeastern United States where it is very common in some areas.
Brown Dog Tick (Rhipicephalus sanguineus )
The brown dog tick (also known as the kennel tick) is found through most of the United States This tick feeds on dogs, but rarely bites people. Unlike the other species of ticks, its life cycle allows it to survive and develop indoors. The brown dog tick is found primarily in kennels or homes with dogs where it may be found hiding in cracks, behind radiators, under rugs and furniture, and on draperies and walls.
The adult is reddish-brown and about 1/8-inch long, and usually attaches around the ears or between the toes of a dog to feed. After feeding, a female may engorge to ½-inch long. She then drops off the dog and crawls into a hiding place where she may lay as many as 3,000 eggs. This tick is tropical in origin and does not survive Illinois winters outdoors. The brown dog tick is not an important carrier of human disease.
Winter Tick (Dermacentor albipictus )
The winter tick is a species that feeds on large mammals like deer, cattle and
horses. Unlike the hard ticks mentioned above, the winter tick attaches to the host as a larva and remains attached throughout its life. Consequently, this tick is rarely encountered by campers or hikers. However, hunters may find the winter tick in large numbers on deer carcasses. Although the winter tick may carry diseases of large wild mammals, it is not known to transmit disease to humans.
Preventing Tick Bites and Disease
The best way to protect yourself against tickborne illness is to avoid tick bites. This includes avoiding known tick- infested areas. However, if you live in or visit wooded areas or areas with tall grass and weeds, follow these precautions to help prevent tick bites and decrease the risk of disease:
- Wear protective clothing such as long-sleeved shirts, long trousers, boots or sturdy shoes and a head covering. (Ticks are easier to detect on light-colored clothing.) Tuck trouser cuffs in socks. Tape the area where pants and socks meet so ticks cannot crawl under clothing.
Prevention and Control of Ticks Around the Home
Make sure the property around your home is unattractive to ticks. Because ticks are sensitive to dry conditions and do not thrive in short vegetation, they are seldom a problem in well-maintained lawns. Keep your grass mowed and keep weeds cut. Clean up items that attract rodents which can carry ticks, such as spilled birdseed, and hiding places like old wood piles. If ticks are present in vegetation along the edge of the property, insecticides labeled for control of ticks can be applied to small areas of high weeds that cannot be mowed. Often, one or two applications per season will be adequate to control ticks in these areas.
Free-roaming dogs and cats are much more likely to encounter ticks than those that are confined to the home or yard. If ticks are found on pets, contact your veterinarian for information about an appropriate tick treatment. Remove the occasional tick found indoors by vacuuming, seal the vacuum bag and place it in the trash. Owners of kennels or homes infested with the brown dog tick may wish to contact a professional pest control company for assistance.
When to Contact a Physician after a Tick Bite
If you experience a rash that looks like a bull's-eye, or a rash anywhere on the body or an unexplained illness accompanied by fever following a tick bite, you should consult your physician and explain that you were bitten by a tick. Disease carried by ticks can be treated with antibiotics. However, the type of antibiotic can vary and individuals should be treated early in the infection.
Fact sheets about symptoms and treatment of tickborne diseases may be obtained from local health departments, by calling the Departments central office at 217-782-2016 or from the Departments Web site at http://www.idph.state.il.us .
Identification of Ticks
During the last several years, about 75 percent of the ticks submitted to Department staff have been identified either as the American dog tick or as the lone star tick. Many people are familiar with the female American dog tick. However, the adults of several species and immature stages must be identified by an entomologist or other professional familiar with ticks. To submit a tick for identification, put it into a leak-proof container with rubbing alcohol along with the date and location where the tick was encountered and contact your local health department for assistance.
This publication is for information and is intended as a guide only. Always read and follow all current label instructions for repellents and pesticides. If any information in these recommendations disagrees with the pesticide label, the label instructions must be followed. For more information, contact the Illinois Department of Public Health, Division of Environmental Health, 525 W. Jefferson St. Springfield, IL 62761; 217-782-5830, TTY (hearing impaired use only) 800-547-0466. Prepared with the assistance of the University of Illinois Extension, University of Illinois Department of Veterinary Pathology and Illinois Natural History Survey.