Burden of Recreational Water Illness Due to Exposure to Cyanobacteria and Their Toxins in Freshwater Beaches in Canada

September 2, 2025 updated by: Ian Young, Toronto Metropolitan University

Burden of Recreational Water Illness Due to Exposure to Cyanobacteria and Their Toxins in Freshwater Beaches in Canada: a Prospective Cohort Study

Swimming and other recreational water activities at public beaches are increasingly popular leisure activities among Canadians. However, harmful algal blooms caused by blue-green algae (i.e., cyanobacteria) have also been increasing reported at Canadian public beaches in recent years. These algal blooms can cause various acute illnesses among recreational water users through ingestion, inhalation of aerosols, or skin contact with contaminated water. In addition, blue-green algae blooms and their toxins can cause illnesses in pets and wildlife. Currently, baseline data are lacking on the risk of recreational water illness from exposure to blue-green algae blooms in Canada. This study will identify the burden of recreational water illness among recreational water users at four targeted beach sites in Ontario, Manitoba and Nova Scotia, over a two-year period. A prospective cohort study design will be used. The investigators will determine the risk of acquiring acute illness outcomes in recreational water users, as well as their pet dogs, that engage in different levels of water contact at beaches at risk of blue-green algae blooms. The investigators will examine differences in illness risks by gender, age, and location. Relationships between cyanobacterial cell counts, toxin levels, and environmental conditions with the risk of acute illness among participants will be determined. Overall, results will provide important data on the risk of recreational water illness from exposure to blue-green algae and their toxins in Canadian beach settings.

Study Overview

Status

Active, not recruiting

Conditions

Intervention / Treatment

Detailed Description

This study will investigate the incidence of recreational water illness due to exposure to cyanobacterial blooms and their toxins in four targeted and popular freshwater beaches in Ontario, Manitoba, and Nova Scotia, Canada. A prospective cohort design and One Health approach will be used. On-site recruitment of recreational water users will be conducted at two beaches per year during the summers of 2024 and 2025. The population of interest includes recreational water users of any age and their pet dogs. After enrollment, an in-person survey will determine beach exposures and confounding factors, and a three-day follow-up survey will ascertain any acute illness outcomes experienced by participants or their dogs. The target sample size is 2500 recreational water users. Water samples will be taken each recruitment day and analyzed for cyanobacterial indicators (pigments), cell counts, and toxin levels. Regression analysis will be conducted to estimate the association with water contact, cyanobacterial levels, and risks of different acute illness outcomes.

Study Type

Observational

Enrollment (Estimated)

2500

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Canada
    • Manitoba
      • Winnipeg, Manitoba, Canada, R0E 0T0
        • Grand Beach
    • Nova Scotia
      • Halifax, Nova Scotia, Canada, B2X 2W5
        • Shubenacadie Canal
    • Ontario
      • Port Perry, Ontario, Canada, L9L 1R2
        • Kinsmen beach
      • Windsor, Ontario, Canada, N0R 1G0
        • Colchester Beach

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Child
  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Sampling Method

Non-Probability Sample

Study Population

Recreational water users of any age, and any pet dogs also present at the beaches/waterfront areas, during the study recruitment days.

Description

Inclusion Criteria:

  • ability to provide informed consent
  • ability to complete the surveys in English or French
  • must not have participated in the study in the past 21 days

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Recreational water users
Recreational water users of any age and their pet dogs present at the beaches and waterfronts in this study during recruitment days.
Behavioral: Cyanobacteria exposure during water contact
Cyanobacteria levels in beach water among participants who report water contact in the beach survey

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of gastrointestinal illness among participants
Time Frame: Within 3 days of beach visit
Gastrointestinal illness is defined as one or more of: (a) diarrhea (≥3 loose stools in 24 hrs); (b) vomiting; (c) nausea with stomach cramps; or (d) nausea or stomach cramps that interfere with regular daily activities (e.g., missed work or school)
Within 3 days of beach visit

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of respiratory illness among participants
Time Frame: Within 3 days of beach visit
Defined as: sore throat, runny or congested nose, difficulty breathing, or cough
Within 3 days of beach visit
Incidence of eye infections among participants
Time Frame: Within 3 days of beach visit
Defined as: eye infection or irritation
Within 3 days of beach visit
Incidence of skin infections among participants
Time Frame: Within 3 days of beach visit
Defined as: rash or itchy skin
Within 3 days of beach visit
Incidence of generalized symptoms among participants
Time Frame: Within 3 days of beach visit
Defined as: headache, fever, fatigue, dizziness, loss of appetite, chills, muscle pain, or general pain
Within 3 days of beach visit

Other Outcome Measures

Outcome Measure
Measure Description
Time Frame
Incidence of illness severity measures among participants
Time Frame: Within 3 days of beach visit
Medical consultations, hospital visits, medication use, and hospitalization
Within 3 days of beach visit

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Toronto Metropolitan University

Collaborators

Health Canada
Ontario Ministry of the Environment, Conservation and Parks
Manitoba Environment and Climate Change
Windsor-Essex County Health Unit
Canadian Veterinary Medical Association

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

June 1, 2024

Primary Completion (Estimated)

September 15, 2025

Study Completion (Estimated)

March 31, 2026

Study Registration Dates

First Submitted

August 28, 2024

First Submitted That Met QC Criteria

August 28, 2024

First Posted (Actual)

August 30, 2024

Study Record Updates

Last Update Posted (Estimated)

September 9, 2025

Last Update Submitted That Met QC Criteria

September 2, 2025

Last Verified

September 1, 2025

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 2324-HQ-000024

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

YES

IPD Plan Description

An anonymized dataset will be shared publicly after results are published.

IPD Sharing Time Frame

Study protocol is already published. Code and dataset will be shared after study publication of results.

IPD Sharing Supporting Information Type

  • STUDY_PROTOCOL
  • SAP
  • ICF
  • ANALYTIC_CODE

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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