Contributors: C.S. Apperson, Extension Entomology Specialist; J.R. Baker, Extension Entomology Specialist; L. Garcia, Entomologist, NC Department of Agriculture; M.G. Waldvogel, Extension Entomology Specialist.
Biology
Ticks are related to mites and spiders. They have four stages of development the egg, larval, nymph, and adult stages. After hatching from the egg, the tick must take a blood meal to complete each stage in its life cycle. Each stage of the tick usually takes a blood meal from a different host. For most ticks, each blood meal is taken from a different type of host.
Ticks are usually active in the spring, summer, and fall; however, the adults of some species are active in the winter. When seeking a blood meal, ticks move from leaf litter, from a crack or crevice along a building foundation, or from another secluded place to grass or shrubs where they attach themselves to an animal as it passes. If a host is not found by fall, most species of ticks move into sheltered sites where they become inactive until spring.
Once it is on a host, a tick crawls upward in search of a place on the skin where it can attach to take a blood meal. The tick's mouth parts are barbed, making it difficult to remove the tick from the skin.
In addition, the tick manufactures a glue to hold the mouthparts in place. The female mates while attached to a host and usually feeds for 8 to 12 days until it is full. By the time it finishes feeding, the female may increase in weight by 100 times. A male tick may attach, but it does not feed as long as the female.
The male tick may mate several times before dying. The female, after mating and feeding, drops to the ground where it lays a mass of eggs in a secluded place such as in a crevice or under leaf litter. Shortly after laying an egg mass, which may contain thousands of eggs, the female dies. The eggs hatch in about two weeks, and the life cycle begins again. Depending upon the species of tick, the life cycle may take as little as a few months or as much as two years.
The American Dog Tick
The adult American dog tick, Dermacentor variabilis, is active in the spring, summer and fall. It lives along woodland paths, in parks, pastures, wastelands, and other shrubby habitats in rural and suburban areas of North Carolina. It is found throughout North Carolina, but is most common in the piedmont. In each stage of its life cycle, this tick may feed on a different animal. For example, the larvae feed only on white-footed field mice and meadow voles or pine voles, whereas nymphs prefer medium-sized mammals such as oppossum or raccoons. Adults prefer humans and dogs as hosts. In North Carolina and throughout the southeastern United States, the American dog tick is the vector of Rocky Mountain spotted fever. However, this species does not transmit Lyme disease.
The Brown Dog Tick
The brown dog tick, Rhipicephalus sanguineus, occurs throughout North Carolina and may be active year round. In all stages, it feeds almost exclusively on dogs and rarely attacks people. Brown dog tick females may lay egg masses in cracks and crevices along building foundations, in pet kennels, and in homes. After a few weeks, several thousand larvae may be climbing on walls, draperies, or furniture. When uncontrolled in kennels, populations of the brown dog tick may grow to extremely high levels.
The Lone Star Tick
All stages of Amblyomma americanum, the lone star tick, readily feed on humans and large wild or domestic animals such as deer and dogs. Adults and nymphs are abundant in the spring and summer months. The mite-like larvae of this species, commonly called seed ticks, are abundant in the fall. In this stage, the lone star tick readily attacks humans. This tick is found in habitats similar to those of the American dog tick. It occurs primarily in the coastal plain, but it may be found in the North Carolina piedmont as well.
The Black-legged Tick
Larvae and nymphs of Ixodes scapularis, the black-legged tick, feed on snakes and lizards. The adults attack large mammals such as dogs, deer, and humans. Adults are active in late fall, in early spring, and in winter when temperatures rise above freezing. The black-legged tick is found in the same habitats and regions of North Carolina as the lone star tick.
Also known as tick typhus, Rocky Mountain spotted fever is caused by a bacteria-like microorganism, Rickettsia rickettsii. Rocky Mountain spotted fever rickettsiae are acquired by an american dog tick when it takes a blood meal from an infected animals. These bacteria are not harmful to most wild and domestic animals, but they are extremely pathogenic to humans and dogs. Rocky Mountain spotted fever is normally a disease of wild animals, but people can be infected while camping or hiking in tick-infested areas if they are bitten by an infected tick. In addition, pets may carry an infected tick into living areas. The disease organisms can also be passed through the egg of an infected tick and from stage to stage in the life cycle. Fortunately, only a small percentage of American dog ticks found in nature are infected.
Symptoms of Rocky Mountain spotted fever include headache, fever, chills, aches, pains, and sometimes nausea. These symptoms are usually accompanied by a rash that starts on the wrists and ankles. Because Rocky Mountain spotted fever is easily cured with antibiotics, a person exhibiting any of these symptoms 2 to 14 days after a tick bite should consult a physician at once. If left untreated, Rocky Mountain spotted fever can cause death.
Lyme Disease
Lyme disease is caused by a spiral-shaped bacterium (called a spirochete), Borrelia burgdorferi. The bacterium is transmitted through the bite of an infected tick. Lyme disease was recognized as a distinct disease in 1975 after several children, living close to each other in the town of Old Lymne, Connecticut, developed arthritis. In the northeastern United States where the disease is prevalent, the black-legged tick, Ixodes scapularis (formerly called the deer tick, Ixodes dammini), is the vector of the Lyme spirochete.
The distribution of this tick is expanding; however, it has not yet been found in North Carolina. The black-legged tick in the Southeast does not tend to bite humans, so many fewer cases of Lyme disease are found. The lone star tick does readily attack humans, but only a small number of spirochete-infected ticks have been collected in the southeast. Like Rocky Mountain spotted, fever, Lyme disease is indigenous to wild animals.
Lyme disease has been divided into three clinical stages. Stage I involves a rash and flu-like symptoms. Within 30 days of infection, a characteristic rash (erythema migrans) occurs at the site of the tick bite. Twenty to 50 percent of Lyme disease patients do not exhibit the rash, which often delays diagnosis of the disease. Erythema migrans may occur as an irregular-shaped red blotch or it may consist of a bright red ring around the bite that gradually expands over several days and clears in the center to form a bull's-eye pattern. The rash can vary in size from 1 to 18 inches. Later, secondary blotch-like skin lesions may occur away from the site of the bite when the spirochete spreads. The rash is usually accompanied by fatigue, headache, stiff neck, muscle aches and pains, and a general feeling of discomfort.
Stage II, which occurs during the next several weeks, includes cardiac and neurological symptoms. Neurological complications occur in about 15 percent of the patients and can involve encephalitis (inflammation of the brain), radiculitis (inflammation of the nerve roots), and Bell's palsy (transitory facial paralysis). In most instances, these symptoms completely disappear after lasting several months. Cardiac abnormalities occur in about 8 percent of patients. The symptoms include dizziness, shortness of breath, and heartbeat irregularities that may require installation of a pacemaker. Within several weeks these symptoms usually disappear.
Stage III is distinguished by arthritic problems that may appear as long as two years after the rash. Patients may experience pain, swelling, and elevated temperature in one or more joints. Some patients may also exhibit sleepwalking, loss of memory, mood changes, and inability to concentrate.
Lyme disease and its complications can be effectively treated with antibiotics. Physicians use different antibiotics against each stage of the disease. With early treatment, the course of Lyme disease is shortened, and the occurrence of late complications, such as arthritis, is reduced. Therefore, it is important to diagnose Lyme disease and administer antibiotic therapy quickly.
Avoiding Tick Bites
The risk of infection with tick-transmitted disease organisms can be greatly reduced by prompt removal of any ticks that have attached. Home "remedies" such as application of petroleum jelly or cleaning fluid or holding a burning cigarette near an attached tick will not cause it to dislodge. They irritate the skin and may kill the tick, making it difficult to remove intact. Disease organisms carried by an engorged tick may penetrate even microscopic breaks in the skin. Here is the best way to remove an attached tick:
Control
Weeds and grass around homes and in public-use areas should be kept mowed to discourage rodent hosts of ticks from becoming established. Reduce exposure to ticks by removing the leaf litter layer around picnic tables, in campsites, and along hiking trails.
Severe tick infestations can be controlled effectively with pesticides. Uniform application is critical to achieving adequate control. If a liquid formulation is used, the ground cover in tick-infested areas should be wetted thoroughly to the soil surface. Apply granular pesticides just before rainfall or water the granules thoroughly to assure that the pesticide is released. Until the treated areas have dried, keep children and pets away. Consult the current North Carolina Agricultural Chemicals Manual for advice on pesticide selection.
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