Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Cyclospora cayetanensis is a foodborne parasite that has caused recent outbreaks from the consumption of contaminated produce. One potential route of contamination of produce with C. cayetanensis is irrigation water. Chemical sanitizers like sodium or calcium hypochlorite that are commonly used to reduce levels of bacterial pathogens Escherichia coli O157:H7 or Salmonella enterica in irrigation water are not effective against parasites like C. cayetanensis. However, sand filtration, commonly used in some modes of agricultural irrigation, can be modified to be effective against foodborne parasites. Experiments conducted here showed that adding zero-valent iron (ZVI) to sand improved the reduction of Eimeria tenella and E. acervulina compared to sand filtration alone. Eimeria species of parasites are genetically related to C. cayetanensis and are commonly used as surrogates in agricultural experiments. This research benefits farmers who grow fruits and vegetables by identifying an effective way to improve irrigation water quality by reducing levels of parasites that have caused recent produce outbreaks.

Technical Abstract: Recurring outbreaks of cyclosporiasis linked to fresh produce demonstrate the need to develop interventions to reduce C. cayetanensis in irrigation water. C. cayetanensis is resistant to commonly used irrigation water treatments, such as chemical sanitizers, making removal of oocysts by filtration the most suitable intervention. This study evaluated the reduction of Eimeria tenella and E. acervulina, as surrogates for C. cayetanensis, in water using filters packed with sand alone or mixtures of sand and zero-valent iron (ZVI). Water inoculated with Eimeria oocysts was filtered through laboratory scale (PVC column) and field scale (swimming pool filter) filters packed with either 100% sand, 35% ZVI/65% sand, or 50% ZVI/50% sand (v/v). Filtered and backflush water was examined microscopically for oocysts. Laboratory scale filters with 50% ZVI reduced 99.9% of E. tenella oocysts, compared to 55.3% with sand alone. Field scale filters reduced 70.5%, 64.7%, and 54.5% of E. acervulina oocysts in water using 50% ZVI, 35% ZVI, and 100% sand, respectively. Filters were backflushed to examine the recovery of these parasites during routine filter media cleaning procedures. Backflush recovery of oocysts ranged from 4.42-16.7%. The addition of ZVI significantly improved the reduction of Eimeria spp. oocysts at both filter scales and should be further investigated as a potential irrigation water intervention.