Irrigated urban vegetable production in Ghana: sources of pathogen contamination and health risk elimination

Abstract

Microbiological water and crop contamination was monitored on urban vegetable farms in Ghana. Faecal coliform and helminth egg contamination levels of irrigation water from drains, streams and shallow wells significantly exceeded WHO recommendations for unrestricted irrigation. High faecal coliform levels exceeding common guidelines for food quality were also recorded on lettuce irrespective of the irrigation water source, with significantly lower coliform concentrations on lettuce irrigated with piped water than with shallow well or stream water. Higher crop contamination levels were observed in the rainy season in spite of lower irrigation frequencies, compared to the dry season. The main species of helminth eggs isolated in water and on lettuce were Ascaris lumbrecoides, Hymenolepis diminuta, Fasciola hepatica and Strogyloides larvae. Results from field trials showed that apart from wastewater, already contaminated soil as well as poultry manure also contribute to crop contamination, but contributions from these sources could be only partially quantified. The need to reduce the potential health risks resulting from faecal coliform and helminth contamination of urban and peri‐urban vegetables thus needs a more holistic approach than a simple focus on irrigation water quality. Copyright © 2005 John Wiley & Sons, Ltd.