Mycotic Rhinitis and Sinusitis in Florida Horses

Abstract

Rhinitis and sinusitis caused by fungal pathogens were studied in biopsy samples submitted from 52 horses distributed throughout subtropical and tropical regions of Florida. Methods included routine histopathology as well as polymerase chain reaction (PCR) with panfungal/panoomycete primers and DNA sequencing on extracted DNA (DNA barcoding). Granulomatous, pyogranulomatous, and fibrinopurulent lesions in nasal and sinus mucosa were associated with signs of upper airway obstruction and noise as well as nasal discharge. Morphologic and histochemical assessment of cases identified 31 cases of zygomycosis/pythiosis plus 1 mixed infection case, 16 cases of phaeohyphomycosis with 2 additional mixed infection cases, and 3 cases caused by other fungi. Morphologic evidence of Aspergillus sp. infection as a superficial copathogen was found in 2 of the mixed fungal infection cases. PCR and DNA sequencing facilitated identification of fungal pathogens in 11 of 52 cases (21%). No evidence of oomycete infection was found. Histomorphologic features of previously unrecognized forms of equine rhinitis/sinusitis were described, including those caused by Flavodon flavus, Curvularia lunata, Exserohilum rostrata, Alternaria alternata, Alternaria sp., Cladophialophora bantiana, Fusarium solani, and Toxicocladosporium irritans. PCR and DNA sequencing using panfungal and oomycete primers with DNA from formalin-fixed and paraffin-embedded specimens successfully identified the pathogen in phaeohyphomycosis (7/18 cases, 39%), zygomycosis/pythiosis (1/32 cases, 3%), and other nonpigmented fungal infections (3/3 cases, 100%). Zygomycosis and phaeohyphomycosis were the most common forms of fungal rhinitis found in Florida horses.

Rhinosinusitis in an Australian mare caused by Flavodon flavus, a recently recognized invasive fungal pathogen of the horse

“…[2][3][4][5] A 2018 North American report described a series of equine mycotic rhinitis cases caused by a variety of fungal agents previously not known to be pathogenic in animals, and one of these included the environmental fungus, Flavodon flavus. 14 The pathogenic potential of F. flavus does not appear to have been reported prior to that study. In the present brief report, we present a case of obstructive rhinosinusitis in an Australian mare caused by F. flavus (NCBI: txid559739).…”

“…15 Basidiomycetes have been reported to produce chlamydospores, which are enlarged vegetative cells formed within hyphae or at hyphal tips and are hypothesized to be rest or survival structures. 13 Although the prior report 14 described the intralesional round structures as chlamydospores, we are cautious in identifying our structures as chlamydospores because hyphae were not observed in our samples. Alternative fungal structures such as yeast cells (e.g.…”

Fungal infection of the upper respiratory tract in horses

“…Based on a recent study from Florida, USA (More et al . 2019), histopathology is very important to obtain the correct diagnosis of mycotic rhinitis and sinusitis since fungal culture and PCR/DNA sequencing can fail to identify the correct organism. In addition, PCR from nasal/fungal specimens may simply represent an environmental contaminant and not the cause of an infection.…”

Subclinical endometritis in a mare by Curvularia spicifera and Escherichia coli co-infection

“…Among them, C. australiensis, C. geniculata, C. hawaiiensis, C. lunata and C. spicifera are the species most frequently isolated from clinical specimens . This pathogen has been described in keratomycosis, rhinitis/sinusitis and mycetomas in horses (Boomker et al 1977, Betbeze et al 2006, More et al 2019.…”