Keratinopathogenic mould fungi and dermatophytes in healthy and diseased hooves of horses

Specimens of hoof horn from 187 horses were examined for a possible relationship between clinically affected hooves and the occurrence of pathogenic fungi. Specimens were taken from the coronary band and from the stratum externum and medium of the coronary horn and transferred on to Sabouraud dextrose agar, with and without cycloheximide, and incubated at 28 degrees C. Dermatophytes and mould fungi were identified by their macroscopic and microscopic characteristics. The 732 isolates could be assigned to 26 species of moulds, two different species of the dermatophyte Microsporum and three different species of the dermatophyte Trichophyton. Depending on their pathogenic potential they were assigned to three groups: (i) fungi known to be keratinopathogenic (Acremonium blochii, Alternaria alternata, Alternaria chlamydospora, Geotrichum candidum, Microsporum ferrugineum, Microsporum gypseum, Scopulariopsis brevicaulis, Trichophyton species, Trichophyton mentagrophytes, Trichophyton sch?nleinii, 57 isolates), (ii) a group of uncertain pathogenicity (223 isolates), and (iii) a group of non-pathogenic species (452 isolates). Eighty per cent of the samples from horses with hoof horn lesions and 66.7 per cent of the samples from horses with slightly affected hoof horn contained fungi of the keratinopathogenic group, whereas only 8.9 per cent of the samples from horses with healthy hoof horn contained fungi of this group. There were no significant correlations between the clinical data and the age, sex or breed of the horses or their bedding and hygiene. Twelve species of fungi were isolated from the air in the horses' stables, but none of them belonged to the keratinopathogenic group.     

Use of a topical disinfectant as part of a hoof care programme for horses with diseases of the hoof capsule

Twenty-three horses with persistent hoof horn defects were treated topically with a hoof disinfectant as part of a hoof care programme for a year. The active ingredients of the disinfectant were a poloaximer-iodine complex, ethylenediamine dihydriodide, isopropyl alcohol and propylene glycol. Hoof trimmings were taken at the start of the study and every six weeks, and examined by scanning and transmission electron microscopy. At the beginning of the study all the horn samples contained large numbers of bacteria, and samples from eight of the horses also had fungal hyphae intermingled with the bacteria. After the application of the hoof disinfectant and adjustments to their diet, there were rapid improvements in the gross appearance of the feet of all the horses; some of them improved within two to three weeks and by 12 weeks the horn quality of all the horses had greatly improved.     

Fungal sinusitis resulting in suspected trigeminal neuropathy as a cause of headshaking in five horses

Primary fungal sinusitis was identified in 5 horses displaying signs of headshaking. All 5 horses had fungal plaques adhered to the infraorbital canal (IOC). Headshaking signs were exhibited by 3 horses prior to treatment and 2 horses after treatment. Standing computed tomography (CT) identified erosion of the IOC in the 2 cases in which it was performed. Fungal culture and PCR identified 3 species of fungi, Rhizomucor pusillus, Scedosporium apiospermum and Aspergillus nidulans which have not previously been described as a cause of sinusitis in horses. Surgical debridement followed by topical antifungal therapy was used in all 5 horses. Recurrence of the fungal plaques in 4 horses necessitated further treatment. The headshaking signs and nasal discharge resolved in 3 horses allowing a return to their previous use. Two horses developed persistent headshaking signs despite multiple treatments. Primary fungal sinusitis should be considered as a cause of headshaking signs in horses, due to a suspected trigeminal neuropathy. Computed tomography is valuable in identifying erosion of the IOC which is not identified with conventional radiography. Three out of the 5 cases were treated successfully but permanent resolution of the fungal infection is difficult to achieve once the bone overlying the infraorbital nerve has been eroded.     

Seasonal effects on the aerobic bacterial and fungal conjunctival flora of normal thoroughbred brood mares in Florida

Objective To evaluate seasonal effects on the presence or absence of fungal and aerobic bacterial flora of the conjunctival fornix of normal Florida Thoroughbred horses. Sample population Both eyes of 100 horses. Procedure Horses with normal anterior segment ophthalmic examinations from three farms in north central Florida were included. Each animal had the ventral conjunctival fornix of each eye swabbed with sterile culturettes. Samples were taken in October, January, April, and July (1999–2000). Aerobic and fungal cultures were plated. Bacterial cultures were reviewed at 24 and 48 h. Fungal cultures were reviewed weekly for 4 weeks. Logistic regression analysis with season as a factor and age of the horse as a covariate was performed. Statistical significance was set at P < 0.01. Results Horses ranged from 3 to 24 years of age, with a median age of 9 years. Twenty‐four genera of bacteria and 35 genera of fungi were recovered. Corynebacterium sp., Staphylococcus sp., Bacillus sp. and Moraxella sp. were the bacteria most frequently isolated. Mold species, dematiaceous mold species, Chrysosporium sp., Cladosporium sp., and Aspergillus sp. were the most frequently recovered fungi. Season did not have a significant effect on the presence of microorganisms isolated for individual horses adjusted for age. Younger horses had an increased incidence of gram‐negative rods and fungal isolates. The number of bacteria and fungi isolated are not uniform across seasons. Conclusion There were no significant differences between the number or type of organisms cultured during the sampling seasons in normal Florida horses. A large range of normal bacterial and fungal flora were isolated from these horses. The number of bacteria and fungi isolated are not uniform across seasons. The likelihood of detecting an organism depends on the horses’ age.     

Ultrastructural observation on the response of equine hoof defects to dietary supplementation with Farrier's Formula

Farrier's Formula feed supplement was added to the diet of 18 horses with two types of hoof horn defects. The first group of horses showed sand cracks and crumbling horn around the nail holes; the second group suffered frequent bruising and had flat feet with collapsed heels. Hoof clippings from both groups were studied in the transmission and scanning electron microscopes. All the horses showed a progressive improvement in the gross and microscopic structure of the hoof horn, starting six weeks after the supplementation began. Once good quality hoof horn had grown there was no relapse during the two year period of the study.     

Fusobacterium necrophorum,and not Dichelobacter nodosus,is associated with equine hoof thrush

The aim of this study was to determine which of the two species, Fusobacterium necrophorum or Dichelobacter nodosus, are associated with hoof thrush in horses. Fourteen hoof samples, collected from eight horses with thrush and 14 samples collected from eight horses with healthy hooves, were examined for the presence of F. necrophorum, Fusobacterium equinum and D. nodosus. Only isolates with phenotypic characteristics representing Fusobacterium could be cultured. Total DNA extracted from the 28 hoof samples was amplified by using DNA primers designed from gene lktA, present in F. necrophorum subsp. necrophorum, F. necrophorum subsp. funduliforme and F. equinum, and gene fimA, present in D. nodosus. The lktA gene was amplified from five of the 14 infected hoof samples and from one hoof sample without thrush. The DNA sequence of the amplified ltkA gene was identical to the lktA gene of the type strain of F. necrophorum (GenBank accession number AF312861). The isolates were phenotypically differentiated from F. equinum. No DNA was amplified using the fimA primer set, suggesting that F. necrophorum, and not D. nodosus, is associated with equine hoof thrush. Hoof thrush in horses is thus caused by F. necrophorum in the absence D. nodosus. This is different from footrot in sheep, goats, cattle and pigs, which is caused by the synergistic action of F. necrophorum and D. nodosus.     

Brittle tail syndrome is an emerging infection in horses caused by a keratinolytic fungus Equicapillimyces hongkongensis gen. nov., sp. nov

The newly described brittle tail syndrome causes weakening and breakage of the tail hair of horses. Extensive mycological and molecular studies showed that a novel fungus Equicapillimyces hongkongensis gen. nov., sp. nov. is the most likely cause of this syndrome. It is a septate branching hyaline mould which grows optimally at 30°C, requires nicotinic acid but is inhibited by cycloheximide, and specifically infects horse hair. Hyphae fill the core of infected hair shafts with short-necked structures resembling ascomata containing banana-shaped septate ascospore-like structures perforating the hair cortex from within. Compared to asymptomatic horses (n=31), horses with clinical signs of the syndrome (n=22) are significantly more likely to have positive E. hongkongensis gen. nov., sp. nov. smear (6.5% vs. 100%), culture (6.5% vs. 72.7%), and PCR (32.3% vs. 100%, P<0.001 for all). No other potential pathogens were found on bacteriological and mycological culture or PCR (for Trichophyton, Microsporum and Epidermophyton). Genotyping of pure E. hongkongensis gen. nov., sp. nov. isolates and their corresponding direct specimens by PCR and sequencing of the 18S rRNA, ITS1-5.8S-ITS2, 28S rRNA, beta-actin, beta-tubulin, and elongation factor 1 alpha showed that they are all identical but unique, and related distantly to fungi mostly in the class Sordariomycetes and the family Ophiostomataceae. Its geographical distribution, environmental or animal reservoirs are still unknown. Besides the ugly appearance of infected horse tails, this fungus may emerge as another equine pathogen if it affects the skin and hoof of horses.     

In vitro degradation of equine keratin by dermatophytes and other keratinophilic fungi

Keratinolytic properties of two dermatophytes (Microsporum gypseum, Trichophyton mentagrophytes) and three moulds (Scopulariopsis brevicaulis, Alternaria alternata, Geotrichum candidum) isolated from diseased equine hooves were examined to improve the understanding of pathogenic mechanisms leading to equine onychomycosis. Equine hoof horn material and skin, as well as hoof keratin and dermal keratin extracted from corresponding tissues, were used as sole carbon and nitrogen sources in five test tubes for each fungus. Within 18 days, supernatants of all tubes were repeatedly examined for keratinolytic activity by SDS-PAGE and Western blot analysis. In addition, fungal growth rates were determined to identify the preferred tissue of the individual fungi. Among the fungi examined, M. gypseum was the most keratinolytic species, followed by T. mentagrophytes and S. brevicaulis. In the concentration applied, the moulds A. alternata and G. candidum showed minimal keratinolytic activity. With respect to growth rates, M. gypseum favoured hoof horn material, S. brevicaulis and G. candidum preferred skin as a keratin source, whereas for the other two fungi no clear preference was detectable.     

Membrane-coating granules and the intercellular cementing substance (membrane-coating material) in the epidermis in different regions of the equine hoof

This study aimed to carry out a comprehensive morphological examination of the structure and ultrastructure of the membrane-coating granules (MCG) and membrane-coating material (MCM) common to all hoof segments as well as segment-specific features in the MCG and MCM regarding their synthesis, structure and biochemical composition. Tissue samples from the hooves of the left front and right hind limb of 20 adult riding horses were used. Samples were preserved and embedded for histological routine methods as well as for histochemical techniques and tracer techniques for light and electron microscopy. The MCM shows a segment-specific structure, biochemical composition and function, which were demonstrated for the different parts of the hoof. The MCM and its properties are related to the segment-specific horn quality. Besides intercellular structural factors the MCM is of major importance for the structural integrity and the biomechanical properties of the hoof horn. The physiological structure and composition of MCM provides explanation for the existence of clinically well-known sites of predilection for hoof disorders such as the White Line Disease. Alterations of the MCM play a role in dysfunction and diseases of the hoof epidermis; they are particularly involved in the pathogenesis of infectious diseases of the hoof.     

In vivo confocal microscopy of equine fungal keratitis

Objective To describe in vivo corneal confocal microscopy of horses with fungal keratitis and correlate findings with clinical, histopathological, and microbiological evaluations of clinical cases and an ex vivo experimental equine fungal keratitis model. Animals studied A total of 12 horses with naturally‐acquired fungal keratitis and ex vivo equine corneas experimentally infected with clinical fungal isolates. Procedures Horses with naturally‐acquired fungal keratitis were examined with a modified Heidelberg Retina Tomograph II and Rostock Cornea Module. Confocal microscopy images of clinical isolates of Aspergillus fumigatus, Fusarium solani, and Candida albicans were obtained by examination of in vitro cultures and experimentally infected ex vivo equine corneas. Results Non‐specific in vivo corneal confocal microscopic findings in horses with fungal keratitis included leukocyte infiltrates, activated keratocytes, anterior stromal dendritic cell infiltrates, and vascularization. Linear, branching, hyper‐reflective structures that were 2–6 μm in width and 200 to >400 μm in length were detected in all horses with filamentous fungal keratitis. Round to oval hyper‐reflective structures that were 2–8 μm in diameter were detected in a horse with yeast fungal keratitis. The in vivo confocal microscopic appearance of the organisms was consistent with fungal morphologies observed during examination of in vitro cultures and infected ex vivo equine corneas. Conclusions In vivo corneal confocal microscopy is a rapid and non‐invasive method of diagnosing fungal keratitis in the horse. This imaging technique is useful for both ulcerative and non‐ulcerative fungal keratitis, and is particularly advantageous for confirming the presence of fungi in deep corneal stromal lesions.     

Influence of different exercise regimes on the proximal hoof circumference in young Thoroughbred horses

Reasons for performing study: Most lameness in horses relates to foot problems and may be associated with changes in hoof shape, but there is a lack of information on the influence of normal exercise on hoof shape. Objectives: To investigate the effect of training on proximal hoof circumference in young Thoroughbred racehorses being prepared for racing. Methods: Thirty‐seven young Thoroughbred racehorses were included in this study. Front hoof circumference immediately below the coronary band was measured weekly with a measuring tape in all horses present at the stable. Most horses accomplished a minimum of 2 training periods at the stable separated by periods of rest on a paddock. One sample t tests were used to evaluate if the mean change per week differed from zero. To estimate the repeatability coefficient, the left proximal hoof circumference of 25 horses was measured 3 times in a random order on one day. Results: Most horses showed a similar pattern of change. The proximal hoof circumference decreased during the training periods (P<0.0001) and increased when the horse was rested (P<0.0001). The decrease of the circumference during the first training period was ?0.66 mm/week on the left and ?0.64 mm/week on the right. During the second training period, this was ?0.58 mm/week on the left and ?0.57 mm/week on the right. During the rest period, the circumference increased by 1.03 mm/week on the left and 1.12 mm/week on the right. The repeatability coefficient for the left circumference was 1.8 mm. Conclusions: Horses showed a decrease in circumference during race training that reversed when they were rested. Potential relevance: Measurement of front hoof circumference is a simple method to assess change in hoof shape. It provides an opportunity to investigate the relationships between specific training, hoof shape and soundness.     

Surgical reconstruction of chronic coronary band avulsions in three horses

Three adult horses were admitted with chronic coronary band avulsions of 2-, 3-, and 46-month durations, respectively. The hoof had a typical appearance in all 3 horses, with a spur of coronary band and associated horn growing at right angles to the hoof wall. Each horse was anesthetized, and the coronary band was reconstructed. Follow-up evaluation of the 3 horses (12, 15, and 23 months after surgery, respectively), revealed healing of all 3 avulsed coronary bands. Mild roughening of the hoof wall distal to the previous avulsion site was observed.     

In vitro fungistatic and fungicidal activities of silver sulfadiazine and natamycin on pathogenic fungi isolated from horses with keratomycosis

OBJECTIVE: To evaluate the in vitro antifungal properties of silver sulfadiazine (SSD) and natamycin against filamentous fungi isolated from eyes of horses with keratomycosis. SAMPLE POPULATION: Filamentous fungal isolates obtained from eyes of keratomycosis-affected horses. PROCEDURES: Fungal culture of ocular samples yielded 6 Fusarium spp; 7 Aspergillus spp; and 1 isolate each of Curvularia, Scopulariopsis, Penicillium, and Chrysosporium. For each fungal isolate, minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) of SSD and natamycin were determined. RESULTS: For all 17 fungal isolates, SSD MIC distribution ranged from < or = 1 to > 64 microg/mL; MIC50 and MIC90 (MICs at which 50% and 90% of organisms were inhibited) were 4 and 32 microg/mL, respectively. The SSD MFC distribution for all isolates was < or = 1 to > 64 microg/mL; MFC50 and MFC90 (MFCs at which 50% and 90% of organisms were killed) were 8 and > 64 microg/mL, respectively. For all fungal isolates, natamycin MIC distribution ranged from 256 to > 1,000 microg/mL; MIC50 and MIC90 were 512 and > 1,000 microg/mL, respectively. The natamycin MFC distribution for all isolates ranged from 512 to > 1,000 microg/mL; MFC(50) and MFC(90) were each > 1,000 microg/mL. CONCLUSIONS AND CLINICAL RELEVANCE: These in vitro data suggest that SSD is fungicidal against the fungal isolates that were obtained from eyes of horses with keratomycosis and that natamycin is fungicidal against some of the isolates at the drug concentrations evaluated. Silver sulfadiazine may be a therapeutic option for equine keratomycosis.     

External characteristics of the lateral aspect of the hoof differ between non-lame and lame horses

During a pre-purchase examination (PPE) there is always a debate about how clinical findings of the hoof different from ideal should be interpreted in relation to future lameness risk and/or unsuitability of the horse for the potential purchaser. The objectives of this study were to describe and compare external angular measurements, linear ratios and hoof capsule characteristics of non-lame and lame feet. Photographs of feet from 300 horses with foot pain and 25 non-lame horses were analysed. Hoof wall, heel and coronary band angles and hoof wall length and height, weight-bearing length, coronary band length and height of the coronary band at dorsal and palmar locations were measured and expressed as linear ratios.Mean hoof wall, heel and coronary band angles were larger in lame compared with non-lame feet; only the ratio of dorsal to palmar coronary band heights and the shape of the coronary band were significantly different between lame and non-lame horses. Growth rings were divergent and horn tubules were non-parallel in lameness of >3 months. At a PPE, a larger ratio of dorsal to palmar coronary band heights in one limb may be indicative of previous lameness in that foot. Changes in coronary band shape and divergent growth rings and horn tubules would suggest a longer duration.     

Scanning electron microscope observations of hoof horn from horses with brittle feet

Two types of defect were observed when hoof clippings from horses with brittle feet were viewed in the scanning electron microscope. The first defect showed a loss of structure and horn in the stratum externum. This defect was remedied after biotin treatment. The second defect showed poor attachment of the horn squames and failed to respond to biotin treatment alone. An improvement in this case was achieved by the addition of powdered limestone to the diet.     

Skeletal forelimb measurements and hoof spread in relation to asymmetry in the bilateral forelimb of horses

Reasons for performing study: Research has highlighted a high frequency of skeletal asymmetries in horses. In addition, research into hoof asymmetries has shown that within a bilateral pair, the hoof with the smaller angle is often subjected to greater loading. There has been limited attention paid to understanding compensatory mechanisms for skeletal asymmetries in the horse; the dynamic structure of the hoof could potentially be acting in a compensatory capacity. Objectives: To investigate the relationship between morphometry of forelimb segments and hoof spread and their incidence of asymmetry. Methods: Ten bilateral measurements of the hoof and forelimb were taken from 34 leisure horses. The relationship between hoof spread and forelimb segment measurements were analysed using a generalised linear model (GLM). Results: In relation to left hoof spread, the GLM identified significant negative relationships with left side measurements (third metacarpal length, elbow height), and significant positive relationships with right side measurements (fetlock height, third metacarpal length, elbow height). In relation to right hoof spread, the GLM identified significant negative relationship with left elbow height, and significant positive relationships with right side measurements (fetlock height, point of shoulder). The difference between the number of horses larger to the left or to the right was found to be significant for point of shoulder height (X²= 4.8, P<0.05), and highly significant for heel height (X²= 9.53, P<0.01) and the third metacarpal length (X²= 7.26, P<0.01). Conclusions and clinical relevance: The study demonstrated considerable asymmetry in left‐right morphometry of the equine limb. The fact that measurements of hoof spread were significantly associated with limb segment measurements could possibly indicate that an interaction exists. Any asymmetry in hoof spread measurements may suggest unequal loading of the limbs, which in turn may contribute to injuries and reduced performance.     

Do hoof cracks represent a superficial hoof-problem?

Fifty-four horses with hoof cracks were referred to the Equine Hospital of the University of Zurich, for treatment. The horses were admitted because of lameness or other symptoms caused by the cracks. Deep or complicated quarter cracks were the most common type of cracks diagnosed. Poor conformation and abnormal hoof shape were the most important causes of hoof crack development, whereas injury to the coronary band was a less frequently encountered cause. Effective treatment of this problem includes corrective shoeing, removing horn from the weight-bearing surface as well as from the crack with a Dremel tool and immobilization of the borders of the crack. However, even with such a therapy, the recurrence rate of hoof cracks was with 20% very high.     

Comparative effectiveness of Sumaq and Neem extract cream,Eniloconazole and glycerine iodine on dermatophytosis in Arabian horses: a randomized clinical trial

Dermatophytosis is a contagious fungal disease among animal communities. The major concerns of dermatophytosis are cost of treatment, difficulty of control, and the public health consequences. The objective of the present study was to compare the clinical efficacy of Sumaq and Neem extract cream with that of traditional treatments, eniloconazole and glycerine iodine, on dermatophytosis in Arabian horses. For this purpose, 37 Arabian horses with dermatophytosis had been used. Fungal isolation and identification for each horse were carried out by standard microbiological procedures. Sumaq (Rhus coriaria Linn.) and Neem (Azadirachta indica) seed extracts were selected based on in vitro effectiveness. Horses were randomly allocated into four groups. The first group (n?=?8) was treated with glycerine iodine 10% daily for 7 days. The second group (n?=?10) was treated using eniloconazole 10% emulsified concentrate four times with 2 days interval. The third group (n?=?11) was treated with Neem seeds extract (20% cream) daily for 10 days, and the fourth group (n?=?8) was treated with Sumaq extract (5% cream) daily for 10 days. Clinical and mycological evaluations were assessed at 0, 7, 14, 21, and 28 days post-treatment. The Sumaq and eniloconazole were more effective on clinical index score after 7 days of treatment followed by Neem seed 20% cream. At 28 days post-treatment, a complete healing was obtained by Sumaq 5% cream and eniloconazole (median clinical sum score?=?zero) followed by Neem (median clinical sum score?=?1.5). Moreover, Dermatophytes spp. was isolated only from two horses, one from Neem group and the other from glycerin iodine group. The present results indicate that Sumaq 5% and Neem seed extract are effective alternative treatment for dermatophytosis in Arabian horses.

     

A gross and histopathological study of an ectopic white line development in equine laminitis

In horses with chronic laminitis, an abnormal horny structure called lamellar wedge, is generated between the hoof wall and the laminar epidermis. To be able to manage horses with chronic laminitis correctly, more information about the pathological state of this abnormal horn is required. The aim of this study was to collect and analyze objective morphological data about the abnormal horn in order to understand its morphology and development. In the study, the abnormal horn was grossly visible on the sagittal hoof section from approximately 20 days after the onset of disease. In the histological observations, the structural characteristics of this abnormal horn were similar to the white line tissue, suggesting it is an ectopic white line. Mean value of the cross-sectional area of the abnormal horn against the distal phalanx section area (A/D) was 0.29 cm(2) SD +/- 0.14 and it finally showed an eight-fold increase over the mean value of normal white line section area against the distal phalanx section area. In conclusion, a large amount of the ectopic white line is thought to be finally able to inhibit normal hoof wall growth, so that it should be resected at the optimum time when would be after one month from the onset of the disease.     

The Effect of Season on Muscle Growth,Fat Deposition,Travel Patterns,and Hoof Growth of Domestic Young Horses

Our objective was to determine the influence of season (winter, spring, summer, and fall) on travel patterns, hoof growth, and longissimus dorsi muscle (LM) height and fat thickness between 13th and 14th ribs in 16 horses aged <4 years (eight males and eight females) of Morgan, Quarter Horse, and Moriesian breeds. Real-time ultrasound images of LM height and fat thickness as well as measures of hoof growth were obtained at the end of each season. Global positioning system tracking was conducted for four randomly selected days and one storm day in each season. Data were analyzed using a linear mixed model procedure in SAS. Season influenced fat deposition (P < .01) with the greatest increase in fall (P < .05) but had minimal effect on muscle growth. Hoof growth was greatest in summer and least in winter (P < .01). The average distance traveled was greater in spring and summer than in fall and winter (P < .01). The horses moved for less time and traveled less distance on storm days (P < .05) compared with nonstorm days. Young horses also traveled less on storm days, which indicates that it may be especially important to provide shelter for them. It was concluded that season influenced fat deposition, distance traveled, and hoof growth of domestic young horses. A better understanding of these factors could help equine professionals manage young horses more efficiently to benefit the horses’ physical well-being.