Tick Fever (Rocky Mountain Spotted Fever)

(Human Granulocytic Ehrlichiosis; Tick Typhus)

Ticks are often carriers of organisms that can cause human disease. One of the most familiar is Rocky Mountain spotted fever, which is transmitted to humans by ticks carrying rickettsia. an organism that is classified as bacteria but which also has some characteristics of viruses. This particular form of tick fever is named for the part of the United States where it was discovered, but occurs in all of the states except Maine, Alaska, and Hawaii.

Various types of hard-shelled (Ixodidae) ticks, especially the wood, dog, and Lone-Star varieties, carry rickettsia organisms. In northern states, people are most likely to contract tick fever from May to September. In the South, where ticks are out the year around, they may be vulnerable during any month.

Symptoms develop 3 to 12 days after a tick bite. The fever comes on suddenly along with chills, a headache, and muscle pain. Body temperature may soar to 104°F (40°C) and remain high for up to three weeks if untreated.

The rash generally appears about the fourth day, quickly spreading to the neck, face, and trunk. At first, the rash is flat and pink, but it soon produces small bruises called petechia. The petechia eventually run together, forming large bruises. Brain inflammation, or encephalitis, may develop, causing agitation, delirium, and eventually coma. The gastrointestinal tract is often involved, with nausea, vomiting, and diarrhea. Other target organs for infection include the lungs, liver, spleen, heart, and kidneys. In severe cases, patients may suffer circulation failure and cardiac arrest.

Another deadly type of tick fever, human granulocytic ehrlichiosis (HGE) was identified in 1995. This disease is transmitted by the deer tick, which also carries Lyme disease. HGE is characterized by the sudden onset of fever, chills, muscle and joint pain, and other flu-like symptoms.

Tick fever is always considered life-threatening. Untreated, it carries a 20-percent mortality rate; early antibiotic therapy can cut this death toll.

Diagnostic Studies and Procedures

A recent tick bite and rapid onset of symptoms are key diagnosing factors. In some cases of spotted fever, however, the rash fails to appear or it develops late, making early diagnosis difficult. The rickettsia may be detected by using special staining techniques of tissue and blood samples. They can also be grown in a laboratory culture, but this should be done only in facilities with protective equipment; otherwise, technicians may be exposed to the disease.

Blood tests showing low white blood cell and platelet counts point to the possibility of HGE. There may be arthritis and other symptoms of Lyme disease also, because the two infections may occur simultaneously.

Medical Treatments

If spotted fever is suspected, antibiotic treatment with tetracycline and/or chloramphenicol in pill form will be started immediately, even before laboratory results are available. For a critically ill patient, drugs are given intravenously.

Doxycycline is the first-choice drug for HGE; tetracycline is also effective. Amoxicillin -- used to treat Lyme disease -- does not work against HGE.

Alternative Therapies

There are no alternative therapies that can cure tick fever.

Self-Treatment

Avoiding tick bites is the best approach. When outdoors in a tick-infested area wear protective clothing, such as high boots, long pants, and long-sleeved shirts that fit tightly at the ankles and wrists. Use an insect repellent that is specifically effective against ticks. Even then, after being outdoors, examine your entire body, including the scalp and body folds, for ticks.

Use special collars, sprays, and shampoos on pets during warm weather. Inspect their coats at least once a day and carefully remove any ticks.

If you do find a tick on your body, pull it out, preferably with a pair of sterilized tweezers. If this is not possible, use clean fingers. Wash the wound with soap and water. Do not burn a tick out or kill it with kerosene or turpentine.

If you are diagnosed with tick fever, rest in bed until fever and other symptoms disappear; this should take only a few days if antibiotic treatment has been started promptly.

Other Tick-Borne Disorders

Lyme disease has become one of the most prevalent tick-bome disorders in the United Stales. Colorado tick fever is a mild viral disease spread by ticks in the Western states. In Africa and South America, ticks spread various forms of typhus, as well as rickettsial diseases similar to spotted fever.

In its early stages, the rash of tick fever can be easily confused with measles, but the spreading pattern is different. Measles starts on the face and trunk and spreads outward, whereas the tick-fever rash begins on the hands and feet and spreads inward.