An observational study in Gastroenteritis, Gastrointestinal Diseases and Eye Infections, sponsored by Toronto Metropolitan University. Active, not recruiting at 4 sites in Canada. Per ClinicalTrials.gov, last updated 2025-09-09.
Sponsored by Toronto Metropolitan University · Observational
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.
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.
237 studies on the registry are indexed under Gastroenteritis; 16 are open to participants now.
This study's planned enrollment of 2,500 is above the median of 606 across 62 observational studies indexed under Gastroenteritis.
Browse Gastroenteritis studies →Toronto Metropolitan University is the lead sponsor of 63 studies on the registry; 9 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Recreational water users of any age, and any pet dogs also present at the beaches/waterfront areas, during the study recruitment days.
Inclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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
Incidence of gastrointestinal illness among participants
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)
Time frame: Within 3 days of beach visit
Incidence of respiratory illness among participants
Defined as: sore throat, runny or congested nose, difficulty breathing, or cough
Time frame: Within 3 days of beach visit
Incidence of eye infections among participants
Defined as: eye infection or irritation
Time frame: Within 3 days of beach visit
Incidence of skin infections among participants
Defined as: rash or itchy skin
Time frame: Within 3 days of beach visit
Incidence of generalized symptoms among participants
Defined as: headache, fever, fatigue, dizziness, loss of appetite, chills, muscle pain, or general pain
Time frame: Within 3 days of beach visit
Incidence of illness severity measures among participants
Medical consultations, hospital visits, medication use, and hospitalization
Time frame: Within 3 days of beach visit
Plan to share: Yes — An anonymized dataset will be shared publicly after results are published.
Supporting information: Study protocol, Statistical analysis plan, Informed consent form, Analytic code
Time frame: Study protocol is already published. Code and dataset will be shared after study publication of results.
Data sharing details ↗ · doi.org
This study is active, not recruiting, as verified in Sep 2025. You cannot join it, but the record below documents what was studied.
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Toronto Metropolitan University