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Eric C. Ledbetter, Erotides C. da Silva, Longying Dong, Sean P. McDonough; Experimental Induction of Acute Acanthamoeba castellanii Keratitis in Cats. Invest. Ophthalmol. Vis. Sci. 2012;53(14):6146.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a feline model of acute Acanthamoeba keratitis using methods that replicate natural routes of infection transmission.
Acanthamoeba castellanii was cultivated axenically to a concentration of 3 x 106 amoebae/mL (90% trophozoites and 10% cysts). Hydrophilic soft contact lenses were incubated with the amoeba suspension for 24 hours at 35 °C. Corneal Acanthamoeba inoculation was performed in laboratory cats by three methods: topical inoculation (0.2 mL) following corneal abrasion, placement of a contaminated contact lens for 7 days, and placement of a contaminated contact lens for 7 days following corneal abrasion. Sham inoculations with parasite-free medium or contact lenses incubated in sterile medium were performed. Cats were monitored by ocular examination and in vivo corneal confocal microscopy for 21 days post-inoculation. Corneal samples and whole globes were collected at intervals for amoeba culture, histopathology, and immunohistochemistry.
All cats in the corneal abrasion groups (infected by topical inoculation or placement of a contaminated contact lens) developed keratitis. Clinical ocular disease was inconsistently detected in cats from the contaminated contact lens only group. Initial corneal lesions were nonulcerative and characterized by an irregular corneal epithelium and multifocal epithelial leukocyte infiltrates. Lesions progressed over 8 to 12 days to corneal epithelial ulceration and diffuse stromal inflammation. Between study days 13 and 21, corneal ulcerations resolved and stromal inflammation consolidated into multifocal subepithelial and stromal infiltrates. Corneal amoebae were detected by culture, in vivo confocal microscopy, histopathology, and immunohistochemistry in cats with keratitis. Neutrophilic and lymphocytic keratoconjunctivitis and anterior uveitis were detected by histopathology. Clinical ocular disease was not detected in cats in the sham inoculation groups. Histopathology was unremarkable and corneal amoebae were not detected in cats in the sham inoculation groups or cats from the infection groups that did not develop clinical ocular disease.
Feline Acanthamoeba keratitis is experimentally transmissible by contaminated contact lenses and topical inoculation following corneal epithelial trauma. Experimentally-induced acute Acanthamoeba keratitis in cats is clinically and histopathologically similar to its human counterpart.
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