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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