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International Notes Lyme Disease -- Canada

From 1977 through May 1989, 30 cases of Lyme disease (LD (Lyme borreliosis)) were reported to Canada's Laboratory Centre for Disease Control (LCDC). Ontario is the only province in which LD is a reportable condition; however, active laboratory surveillance for LD is conducted in other provinces. In Ontario, the diagnosis of LD is based on recognition of erythema migrans (EM), with involvement of at least two of the three organ systems usually affected by LD (joints, nervous system, and cardiovascular system), or EM and an indirect immunofluorescence antibody titer greater than or equal to 1:128 or an enzyme-linked immunosorbent assay optical density greater than or equal to 0.40, or EM and isolation of Borrelia burgdorferi. Without EM, diagnosis is based on involvement of at least one organ system and positive serology or isolation (C. LeBer, Ontario Ministry of Health, personal communication, 1989).

For 25 (83%) of the 30 cases, exposure probably occurred in Canada. Four patients had a documented history of tick bite during travel to the southeastern United States before onset of symptoms; one case was acquired in Germany. Seventeen (68%) of the 25 indigenous cases were reported in Ontario, and five (20%), in Manitoba (Figure 1). The areas in Canada with the highest number of cases border on the American states with the highest reported incidence of LD.

Sixteen (53%) of the 30 cases occurred in 1988. Of the 25 cases for which month of onset was reported, cases occurred most commonly in July (28%) and June (16%). The mean age of LD patients was 40 years (range: 18 months to 70 years). Males accounted for 53% of all cases.

A tick bite was documented for 47% of the patients; the remainder had either no history of a bite or no available information. For 48% of LD patients, EM was documented. The most frequently documented presenting symptom was rash (38%), followed by arthralgia/arthritis (28%) and influenza-like illness (13%). Most had multiple symptoms; five patients had neurologic involvement. Five (17%) of the 30 LD patients were hospitalized. Comment: In several provinces, studies are being planned to determine the prevalence of infected vectors in Canada. The Department of Entomology, University of Manitoba, identified, and the Smithsonian Institution in Washington, D.C., confirmed, two female Ixodes dammini ticks collected in Gunton and Winnipeg, Manitoba, in May and June 1989. These are the first reports of this vector species in Manitoba. The only other Canadian reports are from Long Point, Ontario. Intensive sampling efforts for I. dammini in other regions of Manitoba in 1989 found only Dermacentor variabilis (American dog tick).

To acquire more complete incidence data for Canada, LCDC is interested in receiving reports of any additional cases through provincial/territorial epidemiologists. Adapted from: Canada Diseases Weekly Report 1989;15:135-7 and 1989;15:185, as reported by: MJ Todd, MHSc, AO Carter, MD, Disease Surveillance, Bureau of Communicable Disease Epidemiology, Laboratory Centre for Disease Control, Ottawa, Ontario; TD Galloway, PhD, Dept of Entomology, Univ of Manitoba, Winnipeg.

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