Corneaulcus på häst : jämförelse mellan cytologi, mikrobiologisk odling och kliniska parametrar i en retrospektiv studie

Abstract: Corneal ulcer is frequently diagnosed in horses. Horses seem more prone to complications such as infections and keratomalacia compared to other domestic animals (Ollivier, 2005). Early diagnosis as well as prompt and adequate treatment is essential for the ulcer to heal without complications. Cytology and microbial culture are the diagnostic tests of choice and although microbial culture is regarded golden standard, cytology can generate quick and additional information (Hindley et al., 2016; Keller & Hendrix, 2005; Massa et al., 1999; McLeod et al., 1996). Cytology can, for example, give information about the presence of neutrophils, a cell that frequently contribute to the complicating keratomalacia, and additionally also detect fungus and other inflammatory cells such as eosinophils (Gilger, 2017; Matsumoto et al., 1993; Ollivier, 2005). The aim of this study was to compare cytology and microbial culture in corneal ulcer in horses, as well as to find out if ongoing antimicrobial treatment at the time of sampling was affecting the proportion of positive cultures. The aim was also to investigate any agreement between the clinical findings of the horse and the infectious agent. The study included medical records from 38 corneal ulcers examined at the equine hospital at University Animal Hospital at the Swedish University of Agricultural Sciences during the years 2015 and 2016. The result shows that cytology more often detected infection compared to microbial culture, but also that it is very important to combine the two tests to minimize the risk of missing infections which could lead to further complications. Almost half (46%) of the cultures from ulcers treated with topical antimicrobials were positive. In untreated ulcers the percentage was a little higher (64%). Furthermore, there was a relatively high consistency between cytology and microbial culture regarding detection of infection or not. There was also a high degree of agreement regarding the findings of bacteria on cytology compared to corresponding bacteria on culture when the bacteria were cocci or coccoid. As this is a retrospective study there are many unsure parameters and the material is too small to draw any certain conclusions. However, the results indicate that corneal cytology is a good and important diagnostic test as it generates a rapid result that may contribute with important information regarding the presence of inflammation and infection in corneal ulcers. The cytology should be combined with microbial culture to minimize the risk of not detecting a potentially complicating infection and to provide a better basis for decision making regarding further antimicrobial treatment.