Geographical variations in atopic sensitization in Canada have not been described previously. This study used the standardized protocol of the European Community Respiratory Health Survey-1 (ECRHS-1) to investigate the distribution and predictors of atopic sensitization in six sites across Canada and to compare the results with some ECRHS-1 centers.
Adults aged 20-44 years in six study sites across Canada underwent allergy skin testing using 14 allergens (Dermatophagoides pteronyssinus, Dermatophagoides farinae) cat, cockroach, grasses (Timothy grass, Kentucky grass), molds (Cladosporium herbarium, Alternaria alternata, Aspergillus fumigatus, Penicillium), trees (tree mix, birch, Olea europea), and common ragweed.
The overall prevalence of atopy (skin test over 0 mm to any allergen) was 62.7%. There was significant geographical variation in the prevalence of atopy in the six study sites (lowest 55.6% [95% C.I.51.3-59.9] in Prince Edward Island, highest 66.0 [61.7-70.3] in Montreal) and of sensitization to each of the allergens tested even after adjustment for confounders. When the first eight of the nine allergens in the ECRHS were used to estimate the prevalence of atopic sensitization, the prevalence of atopy in Canada was 57% compared with 35.2% overall for centers in the ECRHS. The prevalence of atopy in Vancouver (57% [52.3-61.8]) was close to that of Portland, Oregon (52.1% [46.2-58.0]).
There was a significant variation in atopic sensitization among different study sites across Canada. The prevalence of atopic sensitization is relatively high in Canada compared with sites in the ECRHS and this may, in part, account for the high prevalence of asthma and asthma symptoms in Canada.
The prevalence of hepatitis C in Canada is not known. There is limited information on most small area populations such as Prince Edward Island.
A retrospective approach was used to obtain detailed information on all cases of hepatitis C identified in Prince Edward Island from December 1990 to September 1995. Cases were reviewed for demographic, clinical and risk factor information, including blood donation and transfusion histories.
There were 54 RIBA confirmed cases of hepatitis C infection included in the Prince Edward Island Hepatitis C Database, of which 38 (70%) were males. Age ranged from 18 to 76 years, with a mean age of 38 years. Twenty-eight (52%) of the cases had a history of injection drug use, and 24 (44%) had received blood or blood products in the past. There were five cases with neither of these risk factors identified.
The results suggest that, in this small, primarily rural population, injection drug use is the most common means of hepatitis C transmission, followed by receipt of blood or blood products.
To determine the zoonotic potential of Cryptosporidium and Giardia in Prince Edward Island (PEI), Canada, 658 human faecal specimens were screened that were submitted to the Queen Elizabeth Hospital diagnostic laboratory. Overall, 143 (22%) samples were Cryptosporidium positive, while three (0.5%) were positive for Giardia. Successful genotyping of 25 Cryptosporidium isolates by sequence analysis of the HSP70 gene revealed that 28 and 72% were C. hominis and C. parvum, respectively. Cryptosporidium isolates from humans and previously genotyped C. parvum from beef cattle were subtyped by sequence analysis of the GP60 gene. Subtyping identified three subtypes belonging to the family IIa. All three subtypes IIaA16G2RI (55%), IIaA16G3RI (22%) and IIaA15G2RI (22%) were found in the animal isolates, while two of the subtypes found in the animals, IIaA16G2RI (80%) and IIaA15G2RI (20%), were also identified in the human isolates. Cryptosporidium infection in humans peaked in April-June. Molecular epidemiological analysis of the human data showed a C. parvum peak in the spring and a relatively smaller peak for C. hominis in July-September. The majority (57%) of human Cryptosporidium isolates were found in children between 5 and 10 years of age. All three Giardia isolates were identified as G. duodenalis assemblage A. The overall Cryptosporidium prevalence in our human samples was high relative to other studies, but because the samples were submitted to a hospital diagnostic laboratory, the results may not be representative of the general population. Further, the presence of the same zoonotic C. parvum subtypes in cattle and human isolates implies that transmission is largely zoonotic and cattle may be a source of sporadic human infections on PEI. The presence of Giardia in people on PEI is rare, and the assemblage A found in humans might originate from humans, livestock or other domestic or wild animals.
We examined the prevalence, population attributable risk (PAR), and clinical characteristics of occupational asthma (OA) in a randomly selected population in six communities in Canada. Our study followed the European Community Respiratory Health Survey protocol. A randomly selected population of 18,701 (87% response rate) persons from the study communities, ranging in age from 20 to 44 yr, completed an initial questionnaire, of whom 2,974 (39% response rate) attended the laboratory and completed supplementary questionnaires. Of these latter individuals, 383 had asthma. Asthma was defined as physician-diagnosed asthma, and adult-onset asthma was defined as a first attack at age 15 yr or older. We used several methods for estimating OA as follows: (1) reporting of a high-risk job (occupation and industry) for OA at the time of asthma onset (Probable OA); (2) reporting of exposure to a substance that may cause OA (Possible OA) while not in a high-risk job at the time of asthma onset; and (3) combination of the PAR for high-risk jobs and exposures. The prevalence (95% confidence interval [CI]) of Probable OA and Possible OA combined was 36.1% (31.3 to 41.0%) among subjects with adult-onset asthma. The occupations most commonly reported in association with OA were nursing in the Probable OA group and clerical and food preparation in the Possible OA group. The clinical characteristics and exposures reported by both groups were similar. The PAR for adult-onset asthma in high-risk jobs and exposures was 18.2%. The assessment of occupation and industry alone, rather than of exposures, may underestimate the contribution of occupational exposures to asthma prevalence.
Reported prevalence rates of asthma vary within and between countries around the world. These differences suggest environmental factors in addition to genetic factors in the cause of the disease and may provide clues for preventive strategies. We examined the variability of asthma-related symptoms and medication use among adults in 6 sites across Canada (Vancouver, Winnipeg, Hamilton, Montreal, Halifax and Prince Edward Island) and compared our findings with those from sites that had participated in a recent European survey.
We used the same sampling strategy and standardized questionnaire as those used in the European Community Respiratory Health Survey (ECRHS). The 6 Canadian sites were selected to represent different environments with respect to climate, air pollution and occupational exposure. Community-based samples of 3000 to 4000 people aged 20-44 years were randomly selected in each site. Subjects were asked to complete the questionnaire by mail between March 1993 and November 1994. Prevalence rates (and 95% confidence intervals [CIs]) of asthma symptoms, self-reported asthma attacks and use of asthma medication were compared across the Canadian sites and with sites that had participated in the ECRHS.
The overall response rate of those selected to receive the questionnaire was 86.5% (range 74.5%-92.8%). The prevalence rates of most asthma symptoms varied significantly among the Canadian sites. For instance, 21.9% (Montreal) to 30.4% (Halifax) of the men and 24.0% (Vancouver) to 35.2% (Halifax) of the women reported wheezing in the year before the survey. Depending on the site, 4.4% to 6.3% of the men and 5.2% to 9.5% of the women reported an asthma attack in the last year, and 4.0% to 6.1% of the men and 4.9% to 9.7% of the women were currently using asthma medication. Prevalence rates of symptoms, asthma attacks and medication use did not change with age, but they were higher among women than among men. Compared with the results from the ECRHS sites, those from the Canadian sites were among the highest.
Significant variation in the prevalence of asthma symptoms, asthma attacks and use of asthma medication between Canadian sites and international sites suggests environmental influences. Different combinations of factors in different sites may be responsible for the high prevalence rates and should be the subject of further research to guide clinical management and public health intervention.
Cites: Thorax. 1999 Dec;54(12):1119-3810567633
Cites: Allergy. 1999 Jul;54(7):716-2110442527
Cites: Am J Respir Crit Care Med. 2000 May;161(5):1563-610806155