Role of Irrigation Water in Crop Contamination by Viruses

Abstract

Foods traditionally eaten raw or receiving minimal processing provide an ideal route for the transmission of viruses. Fruits and vegetables can potentially become contaminated before harvesting by irrigation water, water used for spray application of pesticides, or water used in processing (e.g., washing, hydrocooling with ice, etc.). An increase in the number of produce-associated outbreaks corresponds with the increased consumption of fresh fruits and vegetables and with the expanded global sources of these products over the past two decades (Sivapalasingam et al., 2004). Produceassociated outbreaks have increased from 0.7% of all outbreaks in the 1970s to more than 6% in the 1990s in the United States. In 2002, the number of cases of produce-associated illnesses was almost equal to all of those reported for beef, poultry, and seafood combined (Center for Science in the Public Interest, 2002). Several known and suspected food-borne outbreaks have been ascribed to crops contaminated in the field, suggesting contamination by irrigation or during harvesting (Dentinger et al., 2001; CDC, 2003). Perhaps more significant is the low-level transmission of viruses by food contaminated with irrigation water. Quantitative microbial risk analysis has suggested that low levels of virus in irrigation water can result in a significant level of risk of infection to consumers (Petterson et al., 2001). Stine et al. (2005c) estimated that less than one hepatitis A virus per 10 L of irrigation water could result in a risk exceeding 1 : 10,000 per year considering the efficiency of transfer of the virus to crop and its survival till harvest time. The 1 : 10,000 risk of infection per year is currently the acceptable level used by the United States Environmental Protection Agency for Drinking Water(Regli et al., 1991).