Computer-Generated Dot Maps as an Epidemiologic Tool: Investigating an Outbreak of Toxoplasmosis
1999

Mapping Toxoplasmosis Outbreaks in British Columbia

Sample size: 94 publication Evidence: high

Author Information

Author(s): Steven B. Eng, Denise H. Werker, Arlene S. King, Stephen A. Marion, Alison Bell, Judith L. Issac-Renton, G. Stewart Irwin, William R. Bowie

Primary Institution: Capital Regional District Health Department

Hypothesis

Is the municipal water supply associated with the outbreak of toxoplasmosis?

Conclusion

The study found that the incidence of Toxoplasma gondii infections was significantly higher among residents served by a specific water distribution system.

Supporting Evidence

  • 83 out of 94 acute cases lived in the area served by the Humpback Reservoir.
  • The incidence rate of acute infection was more than three times higher for those served by the Humpback Reservoir.
  • 36 out of 3,812 screened pregnant women were classified as having acute infection.

Takeaway

This study used maps to show that more people got sick from a water source in British Columbia, helping to find out where the problem was.

Methodology

Computer-generated dot maps were used to analyze the geographic distribution of Toxoplasma gondii infections and data from a serologic screening program.

Potential Biases

Potential for misclassifying exposure due to reliance on the Medical Services Plan database.

Limitations

Rates were not adjusted for age or other covariates in the geographic mapping analysis.

Participant Demographics

The study involved residents of the Capital Regional District, including 3,812 pregnant women screened for T. gondii infection.

Statistical Information

P-Value

0.0003

Confidence Interval

95% CI: 1.88-6.63

Statistical Significance

p = 0.0003

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