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The survival and control of protozoan parasites in agricultural environments
Date
2025
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
Protozoan parasites such as Cyclospora cayetanensis and Cryptosporidium parvum pose persistent challenges to food safety due to their resistance to conventional sanitation methods, difficulties in detecting them in complex matrices, and experimental limitations. This dissertation explores protozoan contamination across agricultural systems, tracing pathogen progression from water sources, through crops or soil, and to consumers. A comprehensive literature review of C. cayetanensis highlights critical knowledge gaps, including its unculturable nature and limited genomic data, while establishing Eimeria tenella and C. parvum as valuable experimental surrogates. Laboratory trials demonstrated that, while low concentrations (3-10ppm) of aqueous chlorine and peracetic acid were effective at controlling bacterial pathogens in agricultural water, only high concentrations (>50ppm) meaningfully reduced the infectivity of C. parvum and E. tenella oocysts. In another study, oocyst infectivity was monitored after inoculation onto leafy green produce samples which subsequently underwent a simulated ‘tilling under’ process. In this same study, traditional infectivity-based methods were compared to novel methods which relied on the detection of short-lived mRNAs as a means to establish a culture-independent technique to assess infectivity. Both methods revealed prolonged persistence of C. parvum and E. tenella, with oocysts remaining capable of infecting mammalian cells for up to nine months, while mRNAs remained detectable for twelve months. In the final study, the application of gaseous chlorine dioxide to produce which was artificially contaminated with oocysts of C. parvum and E. tenella showed promise as an alternative means of sanitization, achieving up to 4.69 log reductions in oocyst infectivity on tomatoes without compromising produce quality. This research advances the current understanding of protozoan parasite behavior in food production environments, providing critical insights for improved risk assessment and outbreak prevention.
Description
"At the request of the author or degree granting institution, this graduate work is not available to view or purchase until July 20 2026."--ProQuest abstract/details page.
Keywords
Food microbiology, Foodborne pathogens, Pre-harvest food safety, Protozoan parasites