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Rocky Mountain spotted fever is an acute infectious disease caused by the bacteria-like microorganism, Rickettsia rickettsii. Both the American dog tick and the lone star tick can harbor this microorganism, and bites from infected ticks of these species can give rise to spotted fever cases. Since the peak activity of these ticks occurs in the spring, cases of spotted fever usually occur in the spring or early summer. As many as 16 cases and as few as 0 cases have been reported annually in Indiana over the past 30 years. An average of 6 cases is reported annually in Indiana.
The major symptoms of spotted fever begin 3-10 days after tick attachment. They include headache, chills and fever, and muscle aches. From 1 - 3 days after the fever begins, a rash usually appears, first on the wrists and ankles and then spreads to the rest of the body. When promptly diagnosed, spotted fever can be successfully treated with antibiotics. The patient's recollection of a tick bite is frequently the key factor in a successful diagnosis, treatment and recovery. Conversely, when a prompt diagnosis is not forthcoming, deaths have occasionally occurred. Case fatality rates range from 13-25% in untreated cases.
Lyme Disease
Lyme disease is a chronic, tick-borne infection caused by the bacterial spirochete, Borrelia burgdorferi. The disease is named for the towns of Lyme, and Old Lyme, Connecticut, where it was first discovered in 1975. Lyme disease is now the number one reported vector-borne disease in the United States. Most of the cases are reported from New York and the New England States in the East, from Minnesota and Wisconsin in the Midwest, and from California in the West. However, cases have now been reported from 47 states, including Indiana.
The first case of Lyme disease in Indiana was reported in 1983. However, reports of Lyme disease cases in Indiana have increased in recent years; approximately 25 cases were reported annually during the 1990s. While an unknown percentage of the cases reported each year in Indiana, are acquired out of state, the risk of acquiring Lyme disease through a tick bite received in Indiana is increasing, particularly in the state's northwestern most counties where infected ticks have been collected.
Symptoms of Lyme disease vary from patient to patient. In approximately 90% of infected people, a rash will develop at the site of the tick bite within one month of the bite. This rash, the hallmark of early Lyme disease, begins as a small papule and expands, ranging from several inches to a foot or more in diameter. The rash usually appears reddish but may be pale in the center. It can be either flat or raised, or even blistered or scabbed. Regardless of whether or not a rash appears, other symptoms can occur during this acute phase of infection, including: fatigue, fever, headache, swollen glands and stiffness or pain in the muscles, joints and neck. If these early symptoms are not treated with the appropriate course of antibiotics, the disease may become disseminated. Medical complications of disseminated Lyme disease can involve the heart, nervous system and joints. Diagnosis of Lyme disease is based on clinical findings and serologic (blood) tests.
Ehrlichiosis
Two types of human ehrlichiosis occur in the Midwest, human monocytic ehrlichiosis and human granulocytic ehrlichiosis (sometimes referred to as human anaplasmosis). Human monocytic ehrlichiosis (HME), first reported from Arkansas in 1986, is characterized by fever, headache, muscle aches, nausea and vomiting. The disease can be a serious, but is usually not fatal. The first cases of HME to be reported in Indiana occurred in 1994. Most of the cases have been reported from Indiana's southernmost counties where the lone star tick is most abundant. Lone star ticks infected with Ehrlichia chaffeensis, the cause of human ehrlichiosis, have been collected from Warrick, Spencer Crawford, Perry, Pike and Orange Counties. Human granulocytic ehrlichiosis (HGE), which produces symptoms similar to those of HME, is transmitted by the blacklegged tick. The first case of HGE in Indiana was reported in 2003. Both types of human ehrlichiosis can be treated with antibiotics, such as tetracycline.
STARI (Southern Tick-Associated Rash Illness)
Southern tick-associated rash illness (STARI) has been described in humans residing in southeastern and south-central states and is associated with the bite of the lone star tick. The illness, characterized by a rash similar to that of Lyme disease, has been named Southern tick-associated rash illness (STARI). Spirochetes were isolated from the rash of a STARI patient, who was serologically negative for Lyme disease. These spirochetes could not be grown in the culture medium that supports the growth of Lyme disease spirochetes but DNA analysis indicated that they were Borrelia lonestari, the same bacterium that had previously been found in the lone star tick. Recent studies in Indiana have demonstrated the presence of B. lonestari in lone star ticks in several southern counties.
