AFECCT: Assessing filtration efficacy for Cyclospora control

Outbreaks of cyclosporiasis threaten human health and impose liabilities to growers (Almeria et al, 2019; Dubey, 2020) necessitating better preventative tools. Irrigation water represents a source of contamination (Kitajima et al, 2014). Zero-valent ion (ZVI)/sand filtration improves the microbial quality of agricultural water without disinfectant chemicals. Permeable reactive barriers (PRBs) with bio-sand and ZVI filters remove groundwater chemical contaminants (such as bromate), reduce viral loads by 5-logs, bacterial fecal coliform levels in river water by 1 log CFU, and inactivate E. coli and Listeria. (You et al, 2005; Ingram et al, 2012; Shearer and Kniel, 2018; Marik et al 2019). Inactivation varies with contact time, particle size, solution pH, dissolved oxygen, concentration of ions, and redox potential (Sharma et al. 2020). More than three-log reductions have been achieved using filtration against Cryptosporidium parasites (Nascimento et al, 2020). Filtration has recently been established to enhance surveillance for Cyclospora (Durigan et al. 2020) but has not yet been proven as a means of prevention. Here we propose a series of experiments to determine how well such filters remove, and/or harm, parasites contaminating irrigation water. We will establish assay conditions first using parasite-sized fluorescent microspheres. We will then conduct extensive studies using abundant (non-zoonotic) Eimeria parasites of chickens. Those data will govern experiments directly evaluating the capacity of ZVI filters to mitigate the risk of foodborne cyclosporiasis by removing and/or injuring such parasites. In addition, this work will test new in vitro viability assays, establish whether filter efficacy against parasites can be predicted from widely-used E.coli counts, and will hasten future progress by determining whether fluorescent microspheres accurately model parasite responses to filtration.