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Symptoms

A person who has been bitten by an infected tick usually develops a red spot on the skin that gradually increases in size (see page 126). The center of the spot returns to its normal color after a day or two, leaving a bull’s-eye appearance on the skin that may be painless. In some cases, the skin clears up and the person has no other symptoms. However, in other cases, more red spots appear within a day or two and the person may have a headache, fever, swollen lymph glands, and pain in the joints and muscles. He or she may also feel generally ill and weak.

If Lyme disease is not treated, it progresses to a second stage of illness, in which the disease affects the nervous system and heart. Partial paralysis of the muscles served by the facial nerves and other affected nerves may occur. The person may also develop meningitis (see page 692), which is inflammation of the meninges (the coverings of the brain and spinal cord). Meningitis causes severe headache, sensitivity to light (photophobia), and generalized weakness. Rarely, an irregular heartbeat and inflammation of the heart and pericardium (the heart’s covering) can occur.

If the second stage is not treated, a third stage will occur in which a person may develop chronic arthritis that affects the larger joints such as the knees.

Diagnosis and Treatment

A diagnosis of Lyme disease can be confirmed by blood tests.

Lyme disease is treated with doxycycline or another antibiotic (children are treated with amoxicillin). If Lyme disease is diagnosed and treated in its early stages, the outlook is good. Once chronic arthritis has developed, however, treatment is less successful. Additional treatment may be necessary if symptoms recur.

Rocky Mountain Spotted Fever

Rocky Mountain spotted fever is a potentially life-threatening infection caused by rickettsia bacteria that are transmitted through tick bites. Although ticks that carry the rickettsia bacteria are found all over the United States, the disease most frequently occurs in the Southeast, from Maryland to Georgia. Rocky Mountain spotted fever usually occurs in the spring and summer in people who spend a lot of time outdoors.

Ticks

Ticks are parasites, usually found in wooded areas or tall grass, that feed on animals such as deer, mice, rabbits, and raccoons. A tick bite can be life-threatening because of the viruses and bacteria that ticks carry and transmit as they feed. There are several different types of ticks; each one can transmit a different disease. Some ticks can transmit more than one disease at a time. Diseases transmitted through tick bites include Rocky Mountain spotted fever, Lyme disease (see previous page), and encephalitis (see page 694). Some ticks also harbor a toxin that paralyzes the nerves in the legs and in the trunk. The paralysis is relieved by removing the tick.

Tick (magnified)

A tick embeds its mouth into a person’s skin, then swells as it feeds, sometimes to several times its original size. The skin around the bite hardens into a lump surrounded by a red halo. Usually, the lump subsides after the tick is removed but, in some cases, it can persist, especially if the tick’s head remains in the skin after its body has been removed.

Take the following steps to avoid being bitten by ticks or to detect ticks as soon as possible:

• Use an insect repellent that contains DEET or permethrin. Carefully follow the instructions on the package.

• Wear light-colored clothing with a tight weave to see ticks more easily and avoid having them come in contact with your skin. Always wear shoes or boots, socks, long pants, and long-sleeved shirts. Tuck your pants into your socks, and tuck your shirt into your pants.

• Mow your lawn regularly. Clear out brush and leaf litter. Stack woodpiles neatly in a dry location, preferably off the ground. Remove leaves and the remains of plants from your garden in the fall.

• After being outdoors, inspect your body thoroughly