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Lyme disease is the best known, but by no means the only infection transmitted by tick bites. The highest incidence of Lyme disease (LD) are in the Northeast, Wisconsin and Minnesota. Other tick-transmitted diseases include babesiosis and human granulocytic anaplasmosis (HGA).
Symptoms of the former are similar to malaria, and severity can range from asymptomatic to rapidly fatal. Most infected persons experience a viral-like illness with fever, chills, sweats, myalgia, joint pain, anorexia, nausea, vomiting and fatigue. Immuno-compromised patients are at high risk for severe babesiosis. There are reported cases in southern New England states, including Martha’s Vineyard, Nantucket Island in Massachusetts; and Block Island, RI and eastern Long Island and Shelter Island, NY.
For HGA, clinical manifestations are nonspecific and include fever, chills, headache and myalgia. Most cases are self-limited and resolve in most patients, even without antibiotics.
The principal spreader of these diseases in the U.S. is the juvenile and adult deer tick, Ixodes scapularis and Ixodes pacificus. The tick transmits the spirochete Borrelia burgdorfer during the feeding phase. Although a person may be bitten by an infected tick in an endemic area, the chance of transmission is very small unless the tick has been embedded for at least 36 hours. Only 30% of persons who get Lyme disease recall a tick bite. Additionally, the risk of infection also depends on how much of the person’s blood was ingested by the tick.
Diagnosis of Lyme disease
The Centers for Disease Control (CDC) recommends a two-step testing process. The first step can yield false positives. If the results of the first step are positive or equivocal, the same serum specimen is retested using a different protocol after a delay.
A negative response at six to eight weeks after tick exposure generally indicates no active infection. However, if the test is performed too early (less than six weeks), there may be inadequate antibody response. In addition, if the person took an antibiotic for another reason during this six-week incubation period, there will be a delay in developing a positive response.
Lyme disease does not respond to all antibiotics. The preferred antibiotics include amoxicillin, doxycycline and ceftriaxone and are usually given orally. The doctor will determine whether antibiotics should be given and for what duration, depending on the stage of the infection at the time of diagnosis.
Preventing the tick from accessing your skin is the best form of prevention:
• Wear appropriate clothing when walking or working in a high tick area is important. There are clothing sprays that are also helpful in discouraging the tick from attaching. DEET-based skin sprays are also helpful. For children, some of these sprays may be harmful, so it is important to talk with your child’s doctor about recommendations.
• Family pets that go outside are also a potential source of a tick being brought into the house. Frequent inspection and the use of a tick repellent can decrease this risk.
• When coming in from outside, inspect your skin for possible tick attachment. Favorite areas are the armpits, groin, perineum and in skin folds. Do not pull off the tick, but call your physician for advice and assistance.
Clinical stages of Lyme disease
Early localized infection:
• Erythema migrans (EM) is the only true manifestation of Lyme disease in the United States that is sufficiently distinctive to make a clinical diagnosis without laboratory testing. EM occurs in three to 32 days after an infected tick bite. It starts as a red papule at the bite site. Ticks will seek out dark, moist areas to embed such as the groin, thigh, or axilla. The redness spreads out in a circle with central fading, creating a lesion that resembles a bull’s-eye. Only 50-70% of infected people develop EM.
• Non-specific symptoms, such as fatigue, generalized aching, or lymph node enlargement may precede, accompany, or follow the development of a rash. EM will quickly disappear without treatment so that if the person does not notice the rash and does not have systemic symptoms, they may not be aware of the exposure.
Early disseminated Lyme disease:
• If a person develops multiple lesions it means they have disseminated disease. Aggressive antibiotic treatment is needed to prevent cardiac, rheumatologic or neurological conditions that can develop several months after being infected.
• Cardiac conduction defects occur in 8% of patients with early disseminated Lyme disease. These persons need to be hospitalized for cardiac monitoring before initiating intravenous antibiotic treatment because of the risk of developing temporary, complete heart block.
• Early reversible neurological conditions include painful neuropathies, meningitis, encephalopathy and facial palsy. These conditions can occur in up to 15% of untreated patients.
Late Lyme disease:
• There are a variety of musculoskeletal conditions that develop in late stage LD, including polyarthralgia, tendonitis, bursitis and fibromyalgia. Lyme disease is easily confused with chronic fatigue syndrome. Because of similarity of symptoms, treatment can be significantly delayed if LD is not diagnosed early. Lyme-related arthritis involves multiple joints, including the knees.
• Neurological changes can be progressive and cause a wide range of permanent psychiatric changes.