A pig model of Acanthamoeba keratitis: transmission via contaminated contact lenses.

A model of contact lens-induced Acanthamoeba keratitis was developed in Yucatan micropigs. Pigs fitted with parasite-laden soft contact lenses developed corneal infections that clinically and histopathologically mimicked the human counterpart. Three distinct stages of disease became apparent and were categorized as: acute, condensed infiltrate, and resolution stages. Viable parasites were isolated from corneal scrapings and smears were taken during the acute and condensed infiltrate stages. In addition, cysts could be identified deep within the stroma of histological specimens taken during the resolution stages. The characteristic dense, white ring-like infiltrates, stroma edema, keratic precipitates, and the chronic nature of the infections were similar to those observed in human Acanthamoeba keratitis. Histopathological examination of infected corneas revealed extensive neutrophilic infiltrates, stromal necrosis, and disorganization of the collagen lamellae. The strong correlation between the clinical and histopathologic features of contact lens-induced Acanthamoeba keratitis in the pig as well as the anatomical similarity of the pig eye with the human eye make the porcine model a valuable tool for investigations of the immunology, cell biology, and therapy for Acanthamoeba keratitis.