Academic journal article Canadian Journal of Public Health

Descriptive Analysis of Endemic Cryptosporidiosis Cases Reported in Ontario, 1996-1997

Academic journal article Canadian Journal of Public Health

Descriptive Analysis of Endemic Cryptosporidiosis Cases Reported in Ontario, 1996-1997

Article excerpt


Endemic cryptosporidiosis in Ontario was studied using notifiable disease data from the Ontario Ministry of Health for the years 1996-1997 inclusive. For this study period, 451 endemic cases were identified, corresponding to a provincial mean annual ageand sex-adjusted incidence rate of 2.13 cases per 100,000. Children under five years of age had the highest incidence of disease. Males had a higher incidence than females, except for those 15-19 years of age. Five percent of cases were reported as HIV-positive or having AIDS. The proportion of cases occurring between July and November inclusive (63%) was significantly higher than expected (42%) assuming no seasonal variation (p<0.01). The proportion of rural cases observed (29%) was significantly higher than expected (17%) based on the Ontario population (p<0.01). Travel to or prior residence in an endemic area was identified in 22% of the cases where a risk setting was reported (n=265).


Nous avons erudie les cas endemiques de cryptosporidiose declares en Ontario pour les annees 1996 et 1997 en utilisant la base de donnees des maladies a declaration obligatoire du ministere de la Santa de cette province. Durant la periode de reference, 451 cas endemiques ont etc signals, ce qui correspond at un taux moyen de 2,13 cas pour 100 000 habitants, ajuste selon fage et le sexe. Les enfants de moins de cinq ans presentaient le plus haut taux d'incidence de la maladie. Sauf chez les hommes de 15 at 19 ans, le taux d'incidence chez les hommes etait plus cleve que chez les femmes. Cinq pour cent des cas declares etaient seropositifs pour le VIH ou avaient le sida. La proportion des cas declares entre juillet et novembre inclusivement (63 %) etait sensiblement superieure at celle attendue (42 %) dans I'hypothese qu'il n'y ait eu aucune variation saisonniere (p<0,01). La proportion des cas ruraux observes (29 %) etait elle aussi sensiblement superieure a celle attendue (17 %) par reference i la population de (Ontario (p<0,01). Un voyage ou un sejour dans une region oil la cryptosporidiose est endemique figurait dans 22 % des cas associes la presence d'un milieu a risque (n=265).

Cryptosporidiosis is a significant enteric disease in North America characterized by profuse, watery diarrhea, nausea and abdominal pain.1-3 Outbreaks4,5 and surveys of patients with gastroenteritis6-8 show that the disease is present in the Canadian population. Cryptosporidiosis is currently notifiable in British Columbia, Alberta, Saskatchewan, New Brunswick, and Ontario where the disease was made notifiable in 1996.

Investigation of cryptosporidiosis has focussed principally on outbreaks and specific high-risk populations, particularly immunocompromised individuals. Although outbreaks are well documented, the behaviour of cryptosporidiosis in nonoutbreak settings is relatively unknown. The objectives of this study were to describe the demographic, temporal and spatial distributions, as well as the reported risk factors and symptoms, of endemic cryptosporidiosis in Ontario during the years 1996-1997 inclusive using notifiable disease data. Since such data have potential limitations,9 analyses included an initial assessment of the internal validity of the data.


Data sources

Data used for this study consisted of all cases of cryptosporidiosis reported to the Ontario Ministry of Health between January 1996 and December 1997 through the Reportable Disease Information System (RDIS). At the time of the study, only these two years of data were available. In RDIS, a case of cryptosporidiosis is defined as an individual with clinically compatible signs and symptoms with either (a) demonstration of oocysts in stool or life-cycle stages of the parasite in intestinal biopsy sections, or (b) an epidemiological link to one or more laboratory-confirmed cases. For each case in the database, 15 fields were examined (Table I). …

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