Hoof horn disorders such as brittle hooves, fissures, sand cracks, swellings of the coronary band and white line disease are an important cause of disability in performance horses. Many factors have been shown to affect the quality of the hoof horn including nutrition, hoof trimming and shoeing, exercise, bedding, stable hygiene and hoof care. To some extent the role of infectious agents in hoof disorders has been overlooked. Recent work carried out by Dr Keller and colleagues showed that keratopathogenic fungi play a part in poor hoof quality.
One hundred and eighty seven horses were included in the study, of which 52 showed some degree of horn abnormality. Samples were collected from three points on the hoof: the coronary band, the stratum externum and the stratum medium. They were cultured on Sabouraud dextrose agar at 28C with or without cycloheximide for 28 days. A total of 732 keratopathogenic organisms were isolated, belonging to 26 species of fungi and 2 genera of dermatophytes: Microsporum and Trichophyton.
There was a highly significant correlation between the presence of the keratinopathogenic fungi and dermatophytes and horses with hoof horn lesions. Keratopathogenic organisms were isolated in 32 of 40 horses that had hoof horn lesions, and in 8 of 12 horses with slight horn abnormalities. In contrast, similar organisms were found in only 8.9% of the 135 horses with healthy feet.
The mould Scopulariopsis brevicaulisseemed to be particularly prevalent in the diseased feet. In this study no relation was found between the type of bedding and the incidence of fungal hoof infection. However, certain fungi grow better under certain conditions. For example, Alternaria spp tend to grow better on straw; while others (Chrysosporium spp, Fusarium spp, and Geotrichium spp ) prefer whitewood shavings. The authors suggest that if a specific fungal diagnosis is obtained it might be necessary to change the type of bedding used.
"Our studies show that keratinopathogenic fungi may contribute to hoof lesions" said Dr Keller. "Fungal infection should be considered in cases of hoof disease that do not respond to improved management and nutrition."
For further details see: Keratinopathogenic mould fungi and dermatophytes in healthy and diseased hooves in horses. M. Keller; C. Stanek; S. Krehon and R. Rosengarten. Veterinary Record (2000); 147 ; 619-622.