Lyme disease is one of the most common infectious diseases in the United States. In most cases, treatment is straightforward and recovery is complete. Accurate, timely diagnosis is the key to effective treatment.
What It Is
Lyme disease is due to an infection with the bacterium Borrelia burgdorferi, which is transmitted through the bite of an infected tick. Lyme disease can cause skin rash, joint pain, fever, and other symptoms. Untreated Lyme disease may lead to serious neurologic or cardiac symptoms.
Lyme disease is carried by the black-legged tick, Ixodes scapularis, also called the deer tick, in the East and upper Midwest. The western black-legged tick, Ixodes pacificus, carries the disease on the Pacific coast. Cases of Lyme disease are much rarer in the West than in the East and Upper Midwest.
Who Gets Lyme Disease
There are about 30,000-35,000 cases of Lyme disease diagnosed every year in the United States. Almost all cases occur in 14 states, all in the East and Upper Midwest:
- New Hampshire
- New Jersey
- New York
- Rhode Island
Cases diagnosed in other states may be due to infected ticks in those states, or to individuals who were bitten in a state where the disease is endemic but who were diagnosed in another state.
Children between the ages of 5 and 9, especially boys, have the highest incidence of Lyme disease, but it occurs in people of all ages.
How Lyme Disease is Contracted
Ticks live in wooded areas and grassy areas near woods. They wait for a host at the tips of low vegetation or grass, and grab onto the host when it passes by. They do not jump. The most common tick hosts are humans, white-tailed deer, field mice and other small mammals, and a variety of birds. The peak months for infection are May through August, but tick bites and infection can occur during any month of the year, including in winter.
While ticks can attach anywhere on the human body, they prefer certain areas more than others, especially the groin, beltline, armpits, and scalp. A tick that attaches to the skin will cause irritation or itching, but this may not be enough to lead to its discovery and removal. A tick usually must be attached for 36 to 48 hours to transmit the infection. During this time, it feeds on blood and will become engorged and swollen.
The tick develops and grows from larva to nymph to adult stages, and can bite and infect at any stage. The majority of human infections are due to nymphs, which are about the size of a poppy seed.
Dog ticks (Dermacentor variabilis) do not spread Lyme disease. Dog ticks are larger than deer ticks, and have a characteristic white oval or a white pattern on their backs.
Symptoms of Lyme Disease
- Erythema migrans rash: The earliest symptom of Lyme disease in most cases is a rash that develops from 3 to 30 days after the bite. The rash of Lyme disease is first seen at the site of the bite, and typically grows over time. It may clear in the center, leading to the classic “bulls-eye” rash that was once thought to be necessary for a Lyme disease diagnosis. It is now clear that up to 30% of patients never develop any kind of rash despite being infected.
- Other symptoms: Fever, chills, aches, swollen lymph nodes.
- Arthritis: Arthritis is the second most common symptom of Lyme disease, affecting 30% of patients. It can be quite painful, and may particularly affect the knees.
- Bell’s palsy: Facial palsy occurs in about 9% of patients.
- Other symptoms: radiculoneuropathy, meningitis/encephalitis, carditis (shortness of breath, heart palpitations, chest pain)
Diagnosis of Lyme Disease
The diagnosis of Lyme disease is based on the presence of the signs and symptoms of the disease, and exposure to infected ticks. The patient may not have any awareness of having been bitten.
When a patient presents with the classic erythema migrans rash and has had exposure to infected ticks, treatment may be given without additional testing. In less definitive cases, two-stage laboratory testing may be appropriate.
The Role of Testing
Laboratory tests can be used to confirm a diagnosis of Lyme disease when the signs and symptoms are not definitive, but there is suspicion of infection. According to the Centers for Disease Control, “Laboratory testing is helpful if used correctly and performed with validated methods.”
The CDC recommends a 2-stage test for Lyme disease. The first test is an ELISA (enzyme-linked immunosorbent assay) that detects antibodies against the B. burgdorferi bacterium. This test may give a false-negative result early in the infection (within 2 weeks), including the period when the rash is present. A negative result after this period is considered confirmation of no infection.
The test may give an equivocal or false-positive result at any time. The result should be verified by a Western blot (immunoblot) test. A negative result is considered confirmation of no infection. A positive result confirms the infection and should lead to initiation of therapy.
Treatment of Lyme Disease
Treatment depends on the stage of disease. Patients with early, or localized, Lyme disease (symptoms of rash, flu-like illness, and swollen lymph nodes) should receive 2 to 3 weeks of oral antibiotics. Patients with later-stage, or disseminated Lyme disease (symptoms of joint or muscle pain, carditis, neurologic symptoms) may require a similar course of intravenous antibiotics.
Dr. Robert S Jones DO MS FIDSA, is the Medical Director, Infectious Diseases, at Quest Diagnostics.