A probabilistic model of gastroenteritis risks associated with consumption of street food salads in Kumasi, Ghana: Evaluation of methods to estimate pathogen dose from water, produce or food quality

With a rapidly growing urban population in Kumasi, Ghana, the consumption of street food is increasing. Raw salads, which often accompany street food dishes, are typically composed of perishable vegetables that are grown in close proximity to the city using poor quality water for irrigation. This st...

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Bibliographic Details
Published in:The Science of the total environment 2014-07, Vol.487, p.130-142
Main Authors: Barker, S. Fiona, Amoah, Philip, Drechsel, Pay
Format: Article
Language:English
Subjects:
Air. Soil. Water. Waste. Feeding
Ascaris
Ascaris lumbricoides
Biological and medical sciences
Diarrhoea
Disability Adjusted Life Years (DALYs)
Drinking Water - parasitology
Environment. Living conditions
Estimates
Food Contamination - statistics & numerical data
Food industries
Foods
Fundamental and applied biological sciences. Psychology
Gastroenteritis - epidemiology
General aspects
Ghana - epidemiology
Humans
Hygiene and safety
Medical sciences
Microorganisms
Models, Statistical
Norovirus
Public health. Hygiene
Public health. Hygiene-occupational medicine
Quantitative Microbial Risk Assessment (QMRA)
Risk
Risk Assessment
Rotavirus
Salads
Streets
Vegetables - parasitology
Water Quality
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Summary:With a rapidly growing urban population in Kumasi, Ghana, the consumption of street food is increasing. Raw salads, which often accompany street food dishes, are typically composed of perishable vegetables that are grown in close proximity to the city using poor quality water for irrigation. This study assessed the risk of gastroenteritis illness (caused by rotavirus, norovirus and Ascaris lumbricoides) associated with the consumption of street food salads using Quantitative Microbial Risk Assessment (QMRA). Three different risk assessment models were constructed, based on availability of microbial concentrations: 1) Water — starting from irrigation water quality, 2) Produce — starting from the quality of produce at market, and 3) Street — using microbial quality of street food salad. In the absence of viral concentrations, published ratios between faecal coliforms and viruses were used to estimate the quality of water, produce and salad, and annual disease burdens were determined. Rotavirus dominated the estimates of annual disease burden (~10−3Disability Adjusted Life Years per person per year (DALYs pppy)), although norovirus also exceeded the 10−4DALY threshold for both Produce and Street models. The Water model ignored other on-farm and post-harvest sources of contamination and consistently produced lower estimates of risk; it likely underestimates disease burden and therefore is not recommended. Required log reductions of up to 5.3 (95th percentile) for rotavirus were estimated for the Street model, demonstrating that significant interventions are required to protect the health and safety of street food consumers in Kumasi. Estimates of virus concentrations were a significant source of model uncertainty and more data on pathogen concentrations is needed to refine QMRA estimates of disease burden. Gastroenteritis risk from street food salad. Risks from individual pathogens (top) and combined risk as predicted by three different models (bottom) as compared with 10−4DALY health target (solid vertical bar). [Display omitted] •Annual disease burden from street food salad consumption exceeded 10−4DALY target.•Rotavirus was a key driver of gastroenteritis risk (10−3DALYs per person per year).•Estimates of virus concentrations were a significant source of model uncertainty.•Estimates using irrigation water quality significantly underestimated health risks.•Additional interventions are required to reduce risks to street food consumers.
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2014.03.108