Introduction

Alaska and Canada, together, occupy a vast portion of the Northern Hemisphere, stretching from 41° to 83° latitude and from 179° to 52° longitude (Figure 7.1). The climate varies extensively by region. Northern Alaska and Canada have a polar climate with a brief growing period in the summer months while the sub-arctic regions have severe winters but somewhat longer, warmer summers. The southern part of Canada is temperate with a continental climate of four distinct seasons, where summer lasts from June to September. The occurrence and variety of parasites in both animal and human populations reflect this climatic and geographic diversity.

Canada's population numbers over 31 million and Alaska's, 600 000. Alaska's population is clustered around the larger cities of Juneau and Anchorage with sparse distribution elsewhere. Over 90% of Canada's population is distributed within 300km of the United States border. The population is divided into 10 provinces and three territories.

Using a passive surveillance system, four parasite infections were required to be reported to Statistics Canada up until 2000 by the laboratory making the diagnosis: amoebiasis, giardiasis, malaria, and trichinosis. After 2000, amoebiasis and trichinosis were removed from the list of reportable diseases but cryptosporidiosis and cyclosporiasis were added. Provinces can add other parasites to their list of reportable diseases to reflect provincial interests and public health concerns. For a number of reasons, including a presumed high proportion of asymptomatic infections that never contact a health facility, the initiation of medical treatment based on a clinical diagnosis in the absence of laboratory confirmation, host-parasite dynamics related to

Figure 7.1 Map of Canada and Alaska (United States).

Table 7.1 Number of reported cases of notifiable parasite infections in Canada, by province and territory, and in Alaska, United States, in 1993

Amoebiasis 006*

Giardiasis 007.1

Malaria 084

Trichinosis 124

Population (in thousands)

Alaska

7a

40

598.3

Canada

1782

7063

4859

28753.0

Newfoundland

1

71

00

581.1

Prince Edward Island

2

11

00

131.6

Nova Scotia

9

108

20

923.0

New Brunswick

4

138

00

750.9

Québec

201

748

360

7208.8

Ontario

991

3054

2496

10746.3

Manitoba

50

0

90

1116.0

Saskatchewan

54

446

20

1003.1

Alberta

126

941

340

2662.3

British Columbia

3411

4681

530

3535.1

Yukon

2

22

00

32.0

Northwest Territories

1

56

03

62.9

Note a Giardiasis is not a reportable disease in the United States. * means ICD 9 code number.

the probability of detection of parasites in stool specimens, and the variability in laboratory diagnostic capacity (in terms of personnel, equipment, techniques, etc.), the reporting of parasite infections is considered to be grossly underestimated in both Canada and Alaska. Table 7.1 is provided to show the number of cases of notifiable parasite diseases in 1993 for Alaska and for each Canadian province and territory. Table 7.2 presents the results of the 1987 intestinal parasite prevalence survey of provincial laboratories. Each province and state

Table 7.2 Prevalence (%) of E. histolytica, G. lamblia, non-pathogenic protozoa, and helminths identified in provincial laboratories, Canada, 1984

Province

E. histolytica

G. lamblia

Non-pathogenic protozoaa

Helminths

NFLD

0

1.25

NR

0.53

PEI

0.11

1.92

1.86

0.73

NS

1.55

3.33

18.76

2.23

NB

0.02

1.86

1.89

0.51

QUEb

4.43

13.02

42.38

16.34

ONT

3.75

3.84

29.52

4.87

MANc

0.59

43.99

8.36

4.25

SASK

0.10

5.08

3.03

0.40

ALB

1.28

5.98

14.49

1.54

BC

1.61

4.21

14.11

4.51

CANADA

1.75

4.11

15.76

3.26

Source: Reprinted from Gyorkos et al. (1987). Notes a Includes all protozoa other than E. histolytica and G. lamblia. b Based on mostly reference specimens.

c Excludes reports of Blastocystis hominis and presumed B. hominis. NR - not recorded routinely.

has designated provincial and state laboratories which provide diagnostic, training, and advisory support to hospital-based laboratories and physicians and which maintain active communication with national health authorities (Population and Public Health Branch (Health Canada)) and in the United States, the Centers for Disease Control and Prevention (CDC). These two national agencies provide parasite reference services to the laboratories. Health Canada delegates reference activities in parasite serology to its National Centre for Parasitology-Serology (NCPS).

The parasite infections which will be described in this chapter have been selected to illustrate both the spectrum of endemic parasite infections and those parasites that are most important in terms of prevalence or morbidity, whether imported or endemic (Table 7.3). Where published evidence is lacking, expert opinion has been solicited to provide key points. Each parasite section highlights the prevalence of the infection in addition to selected epidemiological features pertinent in the general Canadian population or high risk groups.

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