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 Confirmed case

Clinical evidence of illness with laboratory confirmation by one of the following methods:

• isolation of Borrelia burgdorferi  (senso lato) from a clinical specimen.

• detection of B. burgdorferi  (senso lato) DNA by PCR testing on synovial fluid, cerebrospinal fluid, EM tissue biopsies or blood.


Clinical evidence of illness with a history of residence in, or visit to, a Lyme disease risk area*, and with laboratory evidence of infection in the form of a positive serologic test using the two-tiered approach which consists of a screening ELISA followed by an immunoblot assay.

Probable case

Clinical evidence of illness without a history of residence in, or visit to, a Lyme disease risk area* and with laboratory evidence of infection in the form of a positive serologic test as defined above under confirmed cases.


Clinician-observed erythema migrans without laboratory evidence but with history of residence in, or visit to, a Lyme disease risk area*

* Lyme disease risk areas occur in Canada and internationally.  In Canada this is defined as a locality in which there is evidence for the occurrence of reproducing populations of known tick vector species (particularly Ixodes scapularis and I. pacificus) and the likely transmission of B. burgdorferi. To identify high risk areas in BC please use: For exposures outside of BC please contact BCCDC.

Clinical Evidence

Objective evidence of Lyme disease includes the following when an alternative explanation is not found:

Lyme disease has three stages if left untreated: i) Early Lyme disease characterised by a red rash (>5cm; called erythema migrans or EM) that spreads from the site of the tick rash (as described below); ii) Early disseminated Lyme disease characterised by multiple EM rashes and/or neurological (facial paralysis or meningitis-like) manifestations and/or heart problems (palpitations caused by heart block) which may last several weeks to months; and iii) Late disseminated Lyme disease which is most commonly intermittent arthritis and may last months to over a year. In detail the manifestations are:

Erythema migrans (EM): a round or oval expanding erythematous area of the skin greater than 5 cm in diameter and enlarging slowly over a period of several days to weeks. It appears one to two weeks (range 3-30 days) after infection and persists for up to eight 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 partially purpuric. Signs of acute or chronic inflammation are not prominent. There is usually little pain, itching, swelling, scaling, exudation or crusting, erosion or ulceration, except that some inflammation associated with the tick bite itself may be present at the very centre of the lesion. Note: An erythematous skin lesion present while a tick vector is still attached or that has developed within 48 hours of detachment is most likely a tick bite hypersensitivity reaction (i.e. a non-infectious process), rather than erythema migrans. Tick bite hypersensitivity reactions are usually < 5 cm in largest diameter, sometimes have an urticarial appearance and typically begin to disappear within 24-48 hours. Diagnosis of EM requires careful examination by a physician to eliminate alternative types of skin rash. Note that it is recommended that physicians would normally treat patients with EM without recourse to serological testing as specific antibodies are often not detectable in early Lyme disease.


Multiple erythema migrans: EM lesions, similar to the single erythema migrans lesions described above, but in multiple locations on the body and may be smaller (< 5cm).

Neurological – 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.

Musculoskeletal – 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 – 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 the early stages of the disease.

SOURCE: Lyme ( )
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