For Providers: Tick-and-Mosquito-Borne Diseases

Lyme Disease

Lyme disease is caused by a spirochete-shaped bacterium called Borrelia burgdorferi. The bacteria is commonly found in mice and is transmitted to humans by the bite of an infected blacklegged tick, Ixodes scapularis, also known as the deer tick. Incidence of Lyme disease has increased steadily, with more than 1700 reported cases in Ohio in 2024. The onset of most Lyme disease cases is in late spring and summer.

Early Signs and Symptoms of Lyme Disease

Signs and symptoms of Lyme disease may begin to manifest 3 to 30 days after a tick bite. In addition to flu-like symptoms of fever, chills, headache, fatigue, swollen lymph nodes and muscle and joint aches, the classic erythema migrans (EM) rash may appear.

The rash occurs in approximately 70-80 percent of infections. It begins at the site of the tick bite an average of 7 days after the bite but may appear 3 to 30 days later. The rash expands gradually over a period of days, reaching up 12 inches across. Sometimes the inner ring begins to clear, resulting in the target or “bullseye” appearance. The rash may feel warm to the touch, but it is rarely itchy or painful.

Later Signs and Symptoms of Lyme Disease

Additional signs and symptoms may not appear until days to months after the tick bite:

• Additional EM rash on other areas of the body (early disseminated)
• Severe headaches and neck stiffness (early disseminated)
• Facial palsy (loss of muscle tone or droop on one or both sides of the face) (early disseminated)
• Shooting pains, numbness or tingling in the hands or feet (early disseminated)
• Heart palpitations or an irregular heartbeat (early disseminated)
• Episodes of dizziness or shortness of breath (early disseminated)
• Intermittent pain in tendons, muscles, joints and bones (late)
• Arthritis with severe joint pain and swelling, particularly the knees and other large joints (late)

Testing

Lyme serology should be considered if the epidemiology as well as signs and symptoms are consistent with possible Lyme disease. A two-tiered serological approach should be performed.

In the initial screening test performed at Nationwide Children’s Hospital, IgM and IgG antibodies to B. burgdorferi are detected in two separate enzyme-linked immunoassays (EIA). This test is intended as an aid in the diagnosis of Lyme disease. Testing is not intended or indicated as a screening procedure for the general population, and it should be done only when symptoms suggest Lyme disease.

Negative Results

• Negative results do not rule out a diagnosis of Lyme disease. Patients in early stages (early localized and early disseminated) of infection may not produce detectable levels of antibody. Antibiotic therapy in early stages may prevent antibody production from reaching diagnostic levels.

Positive Results

• Positive results must be interpreted with caution. Clinical symptoms, epidemiological information and other laboratory test results must all be considered. Following CDC recommendations, Western Blot testing is performed to confirm all positive EIA results.

Confirmation by Western Blot or Enzyme-linked immunoassay (EIA)

• In the standard two-tiered approach, the Western Blot method is used to confirm positive antibody screens. This test should only be used to confirm positives, and it should not be ordered as a stand-alone diagnostic test. More recently, the CDC endorsed a modified two-tiered approach, where the confirmatory Western Blot testing is replaced by EIA testing with B. burgdorferi antigens different than those used in the initial EIA screen.

Treatment

Patients presenting with the EM rash should not be tested and should be treated presumptively for Lyme disease. Those in the early disseminated stage may also be seronegative and require empirical treatment. Treatment with appropriate antibiotics in the early stages of Lyme disease generally results in a rapid and complete recovery, as well as prevention of the late arthritis manifestation. Antibiotics commonly used for oral treatment include doxycycline, amoxicillin or cefuroxime axetil. Doxycycline is contraindicated during pregnancy or lactation but is no longer contraindicated in children under 8 years of age. Patients with certain neurological or cardiac forms of illness may require intravenous treatment with drugs such as ceftriaxone or penicillin.

La Crosse and West Nile, Arboviruses

The arboviruses are a group of viruses transmitted by arthropod vectors, particularly mosquitoes and ticks. The most commonly detected arboviruses in the United States belong to the following families: Alphavirus (Eastern equine encephalitis virus, Western equine encephalitis virus), Flavivirus (St. Louis encephalitis virus, West Nile Virus) and Bunyavirus (La Crosse encephalitis virus). In Ohio, most cases of arboviral infection are due to LaCrosse virus and West Nile virus; specific testing for these viruses should be performed.

Symptoms

The severity of symptoms of La Crosse virus and West Nile virus infection in humans ranges from asymptomatic to severe and requiring hospitalization. While both occur in people of all ages, La Crosse is more common than West Nile in children in the Midwest. Symptoms of La Crosse generally appear 5-15 days after infection and include fever, headache, nausea, vomiting, fatigue and lethargy. In severe cases, neurological symptoms, including seizures, hemiparesis and cognitive abnormalities may occur.

Most people (70-80 percent) who become infected with West Nile virus do not develop any symptoms. About 1 in 5 people who are infected will develop a fever with other symptoms such as headache, body aches, joint pains, vomiting, diarrhea or rash. Most people with this type of West Nile virus disease recover completely, but fatigue and weakness can last for weeks or months. Less than 1 percent of people who are infected will develop a serious neurologic illness such as encephalitis or meningitis with symptoms including headache, high fever, neck stiffness, disorientation, coma, tremors, seizures or paralysis.

People with certain medical conditions, such as cancer, diabetes, hypertension or kidney disease, as well as people who have received organ transplants, are also at greater risk for serious illness from arboviruses. Recovery from severe disease may take several weeks or months, and some of the neurologic effects may be permanent.

Testing

La Crosse Virus or West Nile Virus Antibodies, IgG and IgM

These tests are intended to be used as a means of detecting La Crosse virus- or West Nile virus-specific IgG and IgM in serum or spinal fluid specimens in which there is a clinical suspicion of infection. Because other members of the Flaviviridae family, such as St. Louis encephalitis virus, show extensive cross-reactivity with West Nile virus, confirmatory testing specific to all of these viruses should be performed.

Treatment

In mild to moderate cases, over-the-counter pain relievers can be used to reduce fever and relieve symptoms. In severe cases, patients may need to be hospitalized to receive supportive treatment, such as intravenous fluids, pain medication and nursing care.

No vaccine or specific antiviral treatments for La Crosse virus or West Nile virus infection are available.