Lyme Disease Information for Health Care Professionals

Lyme disease (Borrelia burgdorferi) is transmitted by the bite of infected blacklegged ticks (Ixodes pacificus and Ixodes scapularis).  Although risk is low, it is possible to be bitten by an infected tick anywhere in Canada.  The risk is higher in areas with endemic tick populations, including parts of Ontario, Quebec and Nova Scotia.  Recent studies suggest the range of blacklegged ticks is expanding in Canada.  For more information: Lyme disease: a zoonotic disease of increasing importance to Canadians.  Can Fam Physician.  2008 Oct; 54(10):1381-4.

The most common early manifestation of Lyme disease is a bull’s eye target rash or erythema migrans (EM).  EM is a round or oval expanding erythematous rash greater than 5 cm in diameter and enlarging slowly over a period of several days to weeks. It appears 1-2 weeks (range 3-30 days) after infection and persists for up to 8 weeks. Some lesions are homogeneously erythematous, whereas others have prominent central clearing or a distinctive target-like appearance.  On the lower extremities, the lesion may be purpuric. There is usually minimal pain, itching, swelling, scaling, exudation or crusting associated with EM, though some inflammation may be associated with the tick bite itself at the very centre of the lesion.  An erythematous skin lesion present while a tick vector is still attached or which has developed within 48 h of detachment is most likely a tick bite hypersensitivity reaction (i.e., a non-infectious process). Tick bite hypersensitivity reactions are usually < 5 cm in largest diameter, sometimes have an urticarial appearance, and typically begin to disappear within 24–48 h.

Clinical evidence of disseminated Lyme disease may include:

Early neurological Lyme disease: acute peripheral nervous system involvement including radiculopathy, cranial neuropathy, and mononeuropathy multiplex (multifocal involvement of anatomically unrelated nerves), and CNS involvement including lymphocytic meningitis and, rarely, encephalomyelitis (parenchymal inflammation of brain and/or spinal cord, with focal abnormalities). Late neurologic Lyme disease may present as encephalomyelitis, peripheral neuropathy, or encephalopathy.

Lyme arthritis is a monoarticular or oligoarticular form of arthritis most commonly involving the knee, but other large joints or the tempero-mandibular joint may be involved. Large effusions that are out of proportion to the pain are typical. Lyme arthritis is often intermittent if untreated, with episodes of joint inflammation spontaneously resolving after a few weeks to a few months. Persistent swelling of the same joint for 12 months or more is not a usual presentation.

Cardiac involvement associated with Lyme disease includes intermittent atrioventricular heart block often involving the atrioventricular node, (although heart block may occur at multiple levels), and sometimes associated with myopericarditis. Carditis can occur in early stages of the disease.

For more information: The clinical assessment, treatment, and prevention of Lyme disease, Human Granulocytic Anaplasmosis, and Babesiosis: Clinical practice guidelines by the Infectious Diseases Society of America. Clin Infect Dis 2006; 43(9):1089-134.

For more information: Lyme disease in Canada: Q & A for paediatricians, Canadian Paediatric Society.  Paediatr Child Health 2009:14(3):103-5.

Serologic tests using the two-tier ELISA and Western blot criteria is recommended.  A caution has been published against the use of laboratory tests whose accuracy and clinical usefulness have not been properly validated.  For more information: MMWR Morbidity Mortality Weekly Report: 2005; 54-125. 

Serological testing is recommended when patients have a rash suggestive of erythema migrans outside of the appropriate season in a tick-established area or in an area of the country where the tick is not established. Testing is also suggested for patients with characteristic neurological, cardiac or joint involvement with a reasonable possibility of exposure to black-legged ticks. Immunoglobulin M antibodies are usually detectable within weeks of the onset of symptoms; however, a substantial proportion of patients will not have antibodies present at the time of clinical presentation. Therefore, repeat testing four weeks after an initially negative test is suggested. Antibody measurement by enzyme immunoassay is sensitive but lacks specificity; therefore, a two-step procedure with confirmation of positive enzyme immunoassay results by Western blot is recommended with interpretation of the Western blot results using national guidelines.  Even with the two-step procedure, the likelihood of a false-positive test is high in a low prevalence area; therefore, serological screening of Lyme disease is strongly discouraged.