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

• Conditions: Gastroenteritis; Gastrointestinal Diseases; Eye Infections; Skin Infections; Respiratory Tract Infections; Blue Green Algae Poisoning
• Interventions: Behavioral: Cyanobacteria exposure during water contact

• Registration Number: NCT06579170
• Lead Sponsor: Toronto Metropolitan University

Brief Summary

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.

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 Timeline

• Study Start: 2024-06-01
• Study First Submitted: 2024-08-28
• Study First Submitted QC: 2024-08-28
• Study First Posted: 2024-08-30
• Status Verified: 2025-04
• Last Update Submitted: 2025-04-07
• Last Update Posted: 2025-04-10
• Primary Completion: 2025-09-15
• Study Completion: 2026-03-31

Recruitment & Eligibility

• Status: ENROLLING_BY_INVITATION
• Sex: All
• Target Recruitment: 2500

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

Exclusion Criteria

Not provided

Study & Design

• Study Type: OBSERVATIONAL
• Study Design: Not specified

Arm && Interventions

Group	Intervention	Description
Recreational water users	Cyanobacteria exposure during water contact	Recreational water users of any age and their pet dogs present at the beaches and waterfronts in this study during recruitment days.

Primary Outcome Measures

Name	Time	Method
Incidence of gastrointestinal illness among participants	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)

Secondary Outcome Measures

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

Trial Locations

Locations (4)

Colchester Beach; 🇨🇦 Windsor, Ontario, Canada

Kinsmen beach; 🇨🇦 Port Perry, Ontario, Canada

Grand Beach; 🇨🇦 Winnipeg, Manitoba, Canada

Shubenacadie Canal; 🇨🇦 Halifax, Nova Scotia, Canada