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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Parasitic Diseases Laboratory » Research » Publications at this Location » Publication #415935
Research Project: Foodborne Parasites and their Impact on Food Safety

Location: Animal Parasitic Diseases Laboratory

Title: Morphological and autofluorescence assessment of oocysts differentiate live from dead coccidian parasites

Author
item Valente, Matthew
item Streett, Hannah
item TURNER, RANDI - University Of Georgia
item O'BRIEN, CELIA - Former ARS Employee
item Fournet, Valsin
item Jansen, Michael
item Dubey, Jitender
item Rosenthal, Benjamin
item Jenkins, Mark
item Khan, Asis

Submitted to: International Journal for Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2025
Publication Date: 7/1/2025
Citation: Valente, M., Streett, H.E., Turner, R., O'Brien, C., Fournet, V.M., Jansen, M.A., Dubey, J.P., Rosenthal, B.M., Jenkins, M.C., Khan, A. 2025. Morphological and autofluorescence assessment of oocysts differentiate live from dead coccidian parasites. International Journal for Parasitology. 55(8-9):475-484. https://doi.org/10.1016/j.ijpara.2025.04.003.
DOI: https://doi.org/10.1016/j.ijpara.2025.04.003

Interpretive Summary: To understand and mitigate human health risks posed by foodborne pathogens, produce growers and regulators require tools capable of assessing not only their presence but also their viability. Although being present is a concern, actions to mitigate infection are more urgent if the pathogens are viable. The inability to propagate Cyclospora, either in vitro or in vivo, hinders viability assessment. To overcome these challenges, our group identified the presence of autofluorescence granular structures in dead oocysts using Eimeria as a surrogate. The autofluorescent granular structures in dead parasites markedly increase their total autofluorescence intensity compared to live oocysts, which can be captured using FACS to distinguish live from dead oocysts. Identifying distinguishing morphological features that distinguish dead from live parasites represents a welcome advance with several foreseeable applications.

Technical Abstract: To assess and mitigate foodborne risk, regulatory agencies and produce growers require the means not merely to detect but moreover determine the viability of foodborne eukaryotic pathogens such as Cyclospora cayetanensis. Viability assessment would also aid those employing live attenuated vaccines against coccidiosis, a major problem in poultry production. Therefore, we sought to identify morphological changes differentiating viable from non-viable coccidian oocysts, employing Eimeria acervulina as a tractable model, enabling empirical validation by means of in vivo challenge infections in the natural chicken host. High resolution microscopic examinations identified granular structures that autofluoresce under UV exposure in dead oocysts, greatly intensifying overall autofluorescence in dead oocysts. We harnessed this intensification as a basis to sort live from dead oocysts using a Fluorescence-Activated Cell Sorting (FACS) cell sorter, validating their distinction by documenting infectivity in chickens using the former, and minimal shedding with the latter. Our rapid, sensitive, and robust assay holds promise for application to other species of coccidia, including those important to livestock and public health.