Scanning electron microscopy and fungal culture of hoof horn from horses suffering from onychomycosis

Abstract

Horn samples were taken from the hooves of eight horses with clinical signs of equine onychomycosis in at least one hoof capsule. None of the horses had a documented mycological history. The predominant alterations of the horn capsules were sand cracks, white line disease, brittleness (especially around the nail holes), parakeratosis and bruising. The horn samples were stored in sterile tubes for transportation and transferred onto Sabouraud Dextrose Agar and dermatophyte test agar for mycological examination within 6 h. Fungal cultures were incubated for 30 days at room temperature. Fungal identification was based on colonial morphology and microscopic examination of conidia. Horn samples were also stored at -80°C until used for scanning electron microscopy (SEM). The fungal culture revealed that the hoof horn from all eight horses was infected with keratinophilic fungi. The keratinopathogenic fungi Trichophyton spp and Scopulariopsis brevicaulis were also detected in six horses. SEM revealed severe alterations of the horn structure in horn samples infected with keratinopathogenic fungi compared to horn samples from a sound hoof. The most evident changes were deterioration of the tubular structure of the horn wall, disruption of the horny layers, superficial lysis of cornified cells and the presence of fungal elements. Samples without dermatophyte or Scopulariopsis infection, in contrast, were similar to healthy hoof horn.

Cross-sectional study of the prevalence of and risk factors for hoof disorders in horses in The Netherlands

“…However, aside from investigations on the diseased pododerma of the hoof (i.e. laminitis; Eps de Laat et al, 2016) and the septic components associated with white line disease (WLD; Apprich et al, 2010;Redding and O'Grady, 2012), recent research on the prevalence of and risk factors for hoof disorders in horses is scarce. Hoof disorders can cause lameness and lead to a true dysfunction of a horse, decreased welfare, economic losses for its owners and, eventually, a reduction in its durability (Lloyd and Kaneene, 1997;Floyd and Mansmann, 2007;Collins et al, 2010;Ireland et al, 2013).…”

New methods for isolation of keratolytic bacteria inducing intractable hoof wall cavity (<i>Gidoh</i>) in a horse; double screening procedures of the horn powder agar-translucency test and horn zymography

“…Many direct or supporting lines of evidence have indicated that possible contributors to the formation of the Gidoh include decreasing toughness of the wall based on abnormal anatomical conformation of the foot [2, 18], swelling and softening of the horny structure by water and/or urine [6,7,8,9, 19], neglect of incipient lesions relating to irregular farriery [2], and infection of the wall by microorganisms [1, 2, 4, 5, 12, 13, 15,16,17, 19]. Scientific research data have shown that keratinopathogenic fungi can invade into, and proliferate in, horny structures of the foot [1, 15, 17]. This can result in the collapse of the hoof capsule due to the production of keratolytic enzymes [1, 12].…”

“…Scientific research data have shown that keratinopathogenic fungi can invade into, and proliferate in, horny structures of the foot [1, 15, 17]. This can result in the collapse of the hoof capsule due to the production of keratolytic enzymes [1, 12]. Regardless of many reports of bacteria within wall lesions, no report has as yet scientifically proven that the bacteria isolated from a hoof wall cavity can produce keratolytic enzymes that invade the horn and eventually disrupt the hoof wall.…”