Surface ultrastructure and lodging of Entamoeba histolytica and Giardia lamblia cysts on fruits and vegetables

Abstract

Intestinal protozoan infections remain a global public health concern, particularly when transmitted through contaminated fruits and vegetables. This study investigated whether surface ultrastructures of selected produce create favorable microenvironments for cyst lodging of Entamoeba histolytica and Giardia lamblia. Scanning electron microscopy (SEM) was used to examine Fragaria × ananassa, Coriandrum sativum, Solanum lycopersicum, and Lactuca sativa. Plant surfaces exhibit distinct irregularities, including cavities, crevices, and vein-associated folds, which provide protective sites for cyst retention. Cysts were frequently observed within seed-associated cavities of F. × ananassa, along vein-associated and stomatal depressions in C. sativum, and within surface pits of S. lycopersicum. In L. sativa, the number of cavities did not differ significantly between outer and intermediate leaves (10–12 cavities/100 μm²), whereas inner leaves displayed significantly higher cavity densities (14–18 cavities/100 μm²; p < 0.008), and cysts were commonly found lodged within cavities of the inner leaf, as well as within folds and surface irregularities of the outer leaves. These findings demonstrate that microscopic features of plant surfaces facilitate protozoan persistence, thereby contributing to foodborne transmission. Understanding these interactions underscores the need for improved agricultural handling, food processing strategies, and consumer level education to mitigate the risk of parasitic infections linked to fresh produce.