Lyme disease in humans is caused by three species of Borrelia bacteria. In North America, Lyme disease is caused primarily by Borrelia burgdorferi, while in Europe the disease is caused mainly by B. garnii and B. afzelli. In Ontario, transmission occurs through the bite of infected blacklegged ticks called Ixodes Scapularis or deer ticks.
The overall risk of acquiring Lyme disease in Toronto is low but is increased if doing activities in wooded and brushy areas in eastern parts of Toronto.
Blood sample should be collected in a red-top tube and sent to Public Health Ontario Laboratory.
The first step involves testing using a screening Enzyme Immunoassay (EIA) test.
If initial EIA result is non-reactive, healthcare providers should consider an alternative diagnosis; or in cases where the patient has had symptoms for less than or equal to 30 days, the provider may treat the patient and follow up with a convalescent serum.
If the EIA result is reactive or indeterminate, a confirmatory test using Western Immunoblot assay is performed.
Blood tests may be negative in patients with early-stage Lyme disease or in patients previously treated with antibiotics.
The accuracy of blood tests increases as the infection progresses, although it is recognized that a small proportion of patients with later-stage Lyme disease may test negative.
The stage of infection and the possible impact of treatment on the outcomes of blood testing should be taken into consideration during diagnosis.
If a patient was exposed to other species of Borrelia such as those that occur in Europe:
Provide travel history and request testing for European Lyme disease.
The specimens from these patients are sent to the National Microbiology Laboratory for antibody testing.
A new electronic tick identification platform eTick, is now available in Ontario, where anyone can submit a photo of a tick and receive species identification results within 48 hours. This free publicly available tick identification platform can be used for ticks found on a person, pet or in the environment.
There is no longer an added benefit to continue passive tick surveillance because all of Toronto is considered an estimated risk area. Toronto Public Health continues to perform selective active surveillance activities. It is not recommended to submit ticks to Public Health Ontario (PHO) for clinical purposes.
If you wish to submit a tick to the PHO labs, please visit their website for more information.
Note: The City of Toronto has a prevalence of ticks infected with Borrelia burgdorferi greater than 20 per cent and therefore meets the criteria for consideration of post-exposure prophylaxis.
A single dose of oral doxycycline may be offered to patients of any age when all of the following conditions are met:
Adult or nymph of I. scapularis tick was attached for more than 24 hours; and
Prophylaxis can be started within 72 hours from the time that the tick was removed: and
Person was exposed in an area where ecologic information indicates that the rate of infection of ticks is greater than 20 per cent. This applies to the City of Toronto, and
Doxycycline treatment is not contraindicated
There is effective antibiotic treatment for early localized Lyme disease. Should prophylaxis not be indicated based on the above criteria, the health care provider should watch for signs and symptoms of Lyme disease and treat early.