Papulaspora equi, a rare cause of fungal keratitis

Đurđa Slavić, Kristiina Ruotsalo

Animal Health Laboratory, University of Guelph, Guelph, ON

AHL Newsletter 2020;24(4):19.

Corneal scrapings from a 12-year old Hanoverian mare presented with a non-healing corneal ulcer were submitted for cytology, fungal and bacterial (aerobic and anaerobic) culture to AHL.  The cytology smears contained scattered individual squamous epithelial cells intermixed with moderate numbers of neutrophils.  Mild epithelial cell dysplasia characterized by increased cytoplasmic basophilia and several small aggregates of lytic cellular material were noted.  In among this material were low to moderate numbers of septate, branching fungal hyphae.  Occasional hyphae were also present within the backgrounds of the slides (Fig. 1). 

There was no bacterial growth either on aerobic or on anaerobic culture whereas fungal culture yielded growth of black pigmented fungus.  This fast-growing fungus was submitted to the reference laboratory for final identification and was identified as Papulaspora equi.  Search of scientific literature revealed only one published report of isolation of P. equi from a case of equine keratitis.  It was hypothesized that the fungus was introduced into an eye by contaminated plant material while horse was grazing.  P. equi has also been reported as a rare cause of human keratitis with 5 cases over a 5-year period.  In 2 cases, previous eye injury was reported.  Whereas there is no treatment information available for this equine case, it has been reported that all human cases responded well to conventional topical antifungal medication.   AHL

Figure 1.  A cluster of septate, branching fungal hyphae (an arrow) embedded within lytic cellular debris. (Wright’s stain)  Image courtesy of Katherine Morrison.   

References

1. Satheesh SST et. al.  Series of five cases of Papulaspora equi keratitis. Cornea 2014;33(6):640-643.

2. Shadomy HJ and Dixon DM.  A new Papulaspora species from the infected eye of a horse: Papulaspora equi sp. nov. Mycropathol 1989;106:35-39.