The emergence of Lyme disease in Canada

• Published in: Canadian Medical Association journal (CMAJ) 2009-06, Vol.180 (12), p.1221-1224
• Main Authors: Ogden, Nicholas H, Lindsay, L Robbin, Morshed, Muhammad, Sockett, Paul N, Artsob, Harvey
• Format: Article
• Language: English
• Subjects: Animals; Borrelia burgdorferi; Canada - epidemiology; Care and treatment; Causes of; Development and progression; Diagnosis; Disease control; Endemic Diseases - statistics & numerical data; Health aspects; Humans; Ixodes - growth & development; Life Cycle Stages; Lyme disease; Lyme Disease - diagnosis; Lyme Disease - epidemiology; Lyme Disease - prevention & control; Medical diagnosis; Parasites; Population Surveillance; Prevention; Review
• ISSN: 0820-3946; 1488-2329
• DOI: 10.1503/cmaj.080148

Lyme disease, caused by the bacterium Borrelia burgdorferi and transmitted by tick vectors, is the most commonly reported vector-borne disease in the temperate zone.1 More than 20 000 cases are recorded annually in the United States.2 In about 80% of cases, early Lyme disease is characterized by a skin lesion, erythema migrans, which expands to a diameter of more than 5 cm from the site of the tick bite.3 If left untreated, the disease can progress to early disseminated Lyme disease with neurologic (facial palsy, meningitis and meningoradiculoneuritis, also known as Bannwarth syndrome) and cardiac (usually atrioventricular block, sometimes with myopericarditis) involvement, and then to late disseminated Lyme disease with neurologic manifestations (peripheral neuropathy or encephalomyelitis) and Lyme arthritis.3,4 The number of known endemic areas of Lyme disease in Canada is increasing because the range of I. scapularis is expanding in the eastern and central provinces. National surveillance must be able to identify this changing pattern. Lyme disease is potentially preventable if people wear appropriate clothing and use N,N-diethyl-meta-toluamide (DEET) repellents. Removal of infected ticks from a person within 24 hours of attachment usually prevents transmission of B. burgdorferi,23 and early Lyme disease is usually easily treated with antibiotics.4,24 However, prompt treatment requires recognition of vector ticks and erythema migrans lesions by affected members of the public and prompt diagnosis by clinicians.24 If Lyme disease is not recognized during the early stages, patients may suffer seriously debilitating disease, which may be more difficult to treat.4 Therefore, an important function of surveillance is to inform both the public and clinicians about the local risk level and the need for prudent administration of regimens appropriate for prevention and early diagnosis of Lyme disease. As of 2009, physicians will be required to report clinically confirmed and suspected cases of Lyme disease to the national surveillance authority. Such reporting will assist in identifying the burden associated with this disease. We also advocate using environmental indicators of the risk of Lyme disease (i.e., the occurrence of ticks or environmental data for risk maps) for surveillance, to both support the diagnosis of the disease and to pre-empt its occurrence in humans. Researchers are now using the gold-standard surveillance method of intensive field study to va