Radiographic analysis of the dorsal hoof wall thickness in clinically normal draft horses.

OBJECTIVE: To evaluate the radiographic thickness of the dorsal hoof wall in normal draft horse feet. ANIMALS: 33 adult draft horses with no history of laminitis, no clinically obvious lameness, and visibly unremarkable front feet were included. METHODS: This was a prospective, descriptive study of clinically normal draft horses' front feet. Lateromedial radiographs were acquired of the front feet. A ratio of the dorsal hoof wall thickness to the length of the distal phalanx (DHWP3 ratio) was calculated. RESULTS: The dorsal hoof wall thickness to length of the distal phalanx was calculated as 0.33 ± 0.03 (range of 0.28 to 0.39) in this population of draft horses. CLINICAL RELEVANCE: With very few exceptions, the heterogeneous population of draft horses evaluated in this study had a DHWP3 ratio greater than previously published values in lighter breeds (< 0.30).

Comparison of the broncoalveolar lavage fluid proteomics between foals and adult horses.

Neonates have different cellular composition in their bronchoalveolar lavage fluid (BALF) when compared to foals and adult horses; however, little is known about the non-cellular components of BALF. The objective of this study was to determine the proteomic composition of BALF in neonatal horses and to compare it to that of foals and adult horses. Bronchoalveolar lavage fluid samples of seven neonates (< 1 week age), four 5 to 7-week-old foals, and six adult horses were collected. Quantitative proteomics of the fluid was performed using tandem mass tag labeling followed by high resolution liquid chromatography tandem mass spectrometry and protein relative abundances were compared between groups using exact text. A total of 704 proteins were identified with gene ontology terms and were classified. Of these, 332 proteins were related to the immune system in neonates, foals, and adult horses. The most frequent molecular functions identified were binding and catalytic activity and the most common biological processes were cellular process, metabolic process, and biological regulation. There was a significant difference in the proteome of neonates when compared to foals and to adult horses. Neonates had less relative expression (FDR < 0.01) of many immune-related proteins, including immunoglobulins, proteins involved in the complement cascade, ferritin, BPI fold-containing family B member 1, and macrophage receptor MARCO. This is the first report of equine neonate BALF proteomics and reveals differential abundance of proteins when compared to BALF from adult horses. The lower relative abundance of immune-related proteins in neonates could contribute to their susceptibility to pulmonary infections.

Rhodococcus equi-What is New This Decade?

Foals become infected shortly after birth; most develop subclinical pneumonia and 20% to 30% develop clinical pneumonia that requires treatment. It is now well established that the combination of screening programs based on thoracic ultrasonography and treatment of subclinical foals with antimicrobials has led to the development of resistant Rhodococcus equi strains. Thus, targeted treatment programs are needed. Administration of R equi-specific hyperimmune plasma shortly after birth is beneficial as foals develop less severe pneumonia but does not seem to prevent infection. This article provides a summary of clinically relevant research published during this past decade.

Plasma metabolome of healthy and Rhodococcus equi-infected foals over time.

BACKGROUND: Foals that develop pulmonary ultrasonographic lesions on Rhodococcus equi (R. equi) endemic farms are treated with antibiotics because those at risk of developing clinical pneumonia (~20%) cannot be recognised early. Candidate biomarkers identified using metabolomics may aid targeted treatment strategies against R. equi. OBJECTIVES: (1) To describe how foal ageing affects their plasma metabolome (birth to 8 weeks) and (2) to establish the effects that experimental infection with Rhodococcus equi (R. equi) has on foal metabolome. STUDY DESIGN: Experimental study. METHODS: Nine healthy newborn foals were experimentally infected with R. equi as described in a previous study. Foals were treated with oral antibiotics if they developed clinical pneumonia (n = 4, clinical group) or remained untreated if they showed no signs of disease (n = 5, subclinical group). A group of unchallenged foals (n = 4) was also included in the study. By the end of the study period (8 weeks), all foals were free of disease. This status was confirmed with transtracheal wash fluid evaluation and culture as well as thoracic ultrasonography. Plasma metabolomics was determined by GC-MS weekly for the study duration (8 weeks). RESULTS: Foals' plasma metabolome was altered by ageing (birth to 8 weeks) and experimental infection with R. equi as demonstrated using multivariate statistical analysis. The intensities of 25 and 28 metabolites were altered by ageing and infection (p < 0.05) respectively. Furthermore, 20 metabolites changed by more than 2-fold between clinical and subclinical groups. MAIN LIMITATIONS: The number of foals is limited. Foals were experimentally infected with R. equi. CONCLUSIONS: Ageing and R. equi infection induced changes in the plasma metabolome of foals. These results provide an initial description of foal's plasma metabolome and serve as background for future identification of R. equi pneumonia biomarkers.

INTRODUCTION/CONTEXTE: Les poulains qui développent des lésions pulmonaires échographiques dans les fermes d'élevage où Rhodococcus equi (R. equi) est endémique sont traités avec antibiotiques car ceux à risque de développer des lésions cliniques (~20%) ne peuvent être identifiés précocement. Certains biomarqueurs identifiés par le biais de la métabolomique pourraient aider à orienter les stratégies de traitement pour R. equi. OBJECTIFS: (1) Décrire les changements de métabolome plasmatique qui surviennent chez les poulains en lien avec l'âge (naissance jusqu'à 8 semaines d'âge) et (2) Établir les effets d'une infection expérimentale à Rhodococcus Equi sur le métabolome des poulains. TYPE D'ÉTUDE: Étude expérimentale. MÉTHODES: Neufs poulains nouveaux-nés en santé ont été infectés de façon expérimentale par R. equi tel que décrit précédemment. Ils ont été traités avec des antibiotiques s'ils ont développé une pneumonie clinique (n = 4, groupe clinique) ou ont simplement été suivi dans le temps s'ils n'ont pas montré de signes de la maladie (n = 5, groupe sous-clinique). Un groupe de poulains sains (n = 4) était aussi inclus dans l'étude. À la fin de l'étude (8 semaines), tous les poulains étaient sains tel que confirmé par l'évaluation et la culture de leur fluide de lavage transtrachéal de même qu'à l'échographie thoracique. Les métabolomiques plasmastiques ont été déterminées par GC-MS de façon hebdomadaire pour la durée de l'étude (8 semaines). RÉSULTATS: À la fois l'âge et l'infection expérimentale ont altéré le métabolome plasmatique des poulains tel que démontré par l'analyse statistique multivariée. L'âge a altéré l'intensité de 25 métabolites et l'infection a modifié l'intensité de 28 métabolites (p < 0.05). De plus, 20 métabolites ont changé de plus de 2 fois leur valeur initiale, entre les groupes cliniques et sous-cliniques. LIMITES PRINCIPALES: Le nombre de poulains reste limité. Les poulains ont été infecté par R. equi de façon expérimentale. CONCLUSIONS: Le vieillissement et l'infection par R. equi induisent des changements dans le métabolome plasmatique des poulains. Ces résultats représentent une description initiale du métabolome plasmatique chez le poulain et peuvent servir de base pour l'identification future de biomarqueurs pour la détection de pneumonie à Rhodococcus equi.

Rhodococcus equi foal pneumonia: Update on epidemiology, immunity, treatment and prevention.

Pneumonia in foals caused by the bacterium Rhodococcus equi has a worldwide distribution and is a common cause of disease and death for foals. The purpose of this narrative review was to summarise recent developments pertaining to the epidemiology, immune responses, treatment, and prevention of rhodococcal pneumonia of foals. Screening tests have been used to implement earlier detection and treatment of foals with presumed subclinical R. equi pneumonia to reduce mortality and severity of disease. Unfortunately, this practice has been linked to the emergence of antimicrobial-resistant R. equi in North America. Correlates of protective immunity for R. equi infections of foals remain elusive, but recent evidence indicates that innate immune responses are important both for mediating killing and orchestrating adaptive immune responses. A macrolide antimicrobial in combination with rifampin remains the recommended treatment for foals with R. equi pneumonia. Great need exists to identify which antimicrobial combination is most effective for treating foals with R. equi pneumonia and to limit emergence of antimicrobial-resistant strains. In the absence of an effective vaccine against R. equi, passive immunisation remains the only commercially available method for effectively reducing the incidence of R. equi pneumonia. Because passive immunisation is expensive, labour-intensive and carries risks for foals, great need exists to develop alternative approaches for passive and active immunisation.

The type of anticoagulant used for plasma collection affects in vitro Rhodococcus equi assays.

OBJECTIVE: The efficacy of Rhodococcus equi-specific hyperimmune plasma (HIP) is usually evaluated in vitro. Anticoagulants (AC) used for plasma collection can negatively impact bacterial replication but their effect on R. equi growth has not been evaluated. The aim of this study was to establish the effect that AC routinely used in veterinary medicine (ACD, K2EDTA, Li Heparin, and Na Citrate) have on in vitro R. equi growth. To assess this, in vitro assays commonly used to test HIP efficacy (direct effect on microorganism and macrophage infection), were performed using each AC and non-treated bacteria. RESULTS: There was no direct effect of ACD, Li Heparin or Na Citrate on R. equi growth. These AC significantly (p < 0.05) delayed growth for 12 h following opsonization. The number of R. equi colonies after macrophage infection was significantly (p < 0.05) lower 72 h post-opsonization with Na Citrate. K2EDTA inhibited the formation of R. equi colonies by 12 h in all the assays. In conclusion, AC should be taken into consideration when interpreting in vitro results as their negative effect on bacterial growth may be mistakenly interpreted as HIP efficacy. ACD and Li Heparin appear more appropriate for the selected assays.

Plasma lipidome of healthy and Rhodococcus equi-infected foals over time.

BACKGROUND: Many foals that develop thoracic ultrasonographic lesions as a result of Rhodococcus equi infection heal on their own. However, most of these foals receive antimicrobials because foals at risk of developing clinical pneumonia cannot be identified. Untargeted lipidomics is useful to identify candidate biomarkers. OBJECTIVES: (a) To describe the changes that occur in foal lipidomics as a result of ageing (birth to 8 weeks) and (b) To compare these results with those observed in foals after experimental infection with R. equi. STUDY DESIGN: Experimental study. METHODS: Healthy newborn foals (n = 9) were challenged with R. equi intratracheally the first week of life. Foals were treated with antimicrobials if they developed clinical pneumonia (n = 4, "clinical group") or were closely monitored if they showed no signs of disease (n = 5 "subclinical group"). An unchallenged group (n = 4) was also included. All foals were free of disease (transtracheal wash fluid evaluation and culture as well as thoracic ultrasonography) by 8 weeks of life. Plasma lipidomics was determined by LC-MS weekly for the study duration (8 weeks). RESULTS: Both ageing and experimental infection altered the foal's plasma lipidome as demonstrated by multivariate statistical analysis. The intensities of 31 lipids were altered by ageing and 12 by infection (P < .05). Furthermore, nine lipids changed by more than twofold between clinical and subclinical groups. MAIN LIMITATIONS: The number of foals is limited. Foals were experimentally challenged with R. equi. CONCLUSIONS: Ageing and R. equi infection induced changes in the plasma lipidome of foals. These experimental results provide the background for future work in the discovery of earlier biomarkers of R. equi pneumonia. Early identification of foals at risk of developing clinical pneumonia is key in order to decrease antimicrobial use and development of antimicrobial resistance.

Relative Deficiency in Albumin Methionine Content is Associated With Decreased Antioxidant Capacity of Equine Plasma.

Relative to other species, horses seem particularly susceptible to oxidative stress. Plasma albumin plays an important role in preventing oxidative damage, in part due to its methionine (MET) content. Equine albumin is highly unusual in that it contains no MET residues. Whether or not this causes deficient antioxidant capacity in equine plasma relative to that of other species has not yet been explored. The objective of this study was to compare the redox status of equine (no MET) to that of bovine (moderate amount of MET) plasma. Plasma was collected from healthy, nonpregnant Quarter Horse mares (n = 10) and adult, healthy, nonpregnant, dried Holstein cows (n = 15). Measures of total antioxidant capacity and oxidative stress were assessed for each plasma sample using multiple commercially available assays: total antioxidant capacity, thiol detection, thiobarbituric acid reactive substances, and advanced oxidation protein products. Plasma from horses had significantly (P < .05) lower thiol content and thiobarbituric and reactive substances and higher advanced oxidation protein products than plasma from cattle. A difference in total antioxidant capacity was not observed; however, our study was underpowered to establish a meaningful comparison. Based on these findings, the lack of MET in equine albumin appears to translate to a lower antioxidant capacity of equine plasma. Our findings are consistent with previous reports in other species that identify MET as having an important role in the antioxidant capacity of albumin. Our results also highlight the complex system of antioxidant defenses in plasma that counteract the harmful effects of oxidants.

Equine Coronavirus-Associated Colitis in Horses: A Retrospective Study.

Equine coronavirus (ECoV) is a known cause of fever, anorexia, and lethargy in adult horses. Although there are multiple reports of ECoV outbreaks, less is known about the clinical presentation of individual horses during a nonoutbreak situation. The purpose of this study was to describe the clinical presentation of horses diagnosed with ECoV infection that were not associated with an outbreak. Medical records of all horses admitted to Washington State University, Veterinary Teaching Hospital, during an 8-year period were reviewed (2010-2018). The five horses included in this study were older than 1 year of age, were diagnosed with colitis, tested positive for ECoV using real-time polymerase chain reaction, and were negative to other enteric pathogens. Interestingly, 4 of 5 horses had moderate to severe diarrhea, 3 had abnormal large colon ultrasonography, 2 had transient ventricular tachycardia and 2 had clinicopathologic evidence of liver dysfunction. ECoV should be included as a differential diagnosis for individual horses presenting with anorexia, fever, lethargy, and colitis. Early identification of ECoV cases is key to implement appropriate biosecurity measures to prevent the potential spread of this disease.

Strain-to-strain variation of Rhodococcus equi growth and biofilm formation in vitro.

OBJECTIVE: Rhodococcus equi is an opportunistic pathogen that causes disease worldwide in young foals and immunocompromised humans. The interactions of R. equi with the host immune system have been described; however, most studies have been conducted using a few well-characterized strains. Because biological differences between R. equi strains are not well characterized, it is unknown if experimental results will replicate when different strains are used. Therefore, our objective was to compare the growth and biofilm formation of low-passage-rate clinical isolates of R. equi to higher-passage-rate, commonly studied isolates to determine whether strain-to-strain variation exists. RESULTS: Twelve strains were used: 103+, ATCC 33701, UKVDL206 103S harboring a GFP-expressing plasmid, a plasmid-cured 33701 (higher-passage-rate) and seven low-passage clinical isolates. Generation time in liquid revealed fast, moderate-fast, moderate-slow, and slow-growing isolates. The higher-passage-rate isolates were among the moderate-slow growing strains. A strain's rate of growth did not correspond to its ability to form biofilm nor to its colony size on solid media. Based on our results, care should be taken not to extrapolate in vitro work that may be conducted using different R. equi strains. Further work is needed to evaluate the effect that the observed differences may have on experimental results.

Rhodococcus equi-specific hyperimmune plasma administration decreases faecal shedding of pathogenic R. equi in foals.

Rhodococcus equi is the most common cause of pneumonia in young foals. Pneumonic foals are an important source of environmental contamination as they shed higher amounts of R. equi in their faeces than unaffected foals. As R. equi-specific hyperimmune plasma (HIP) lessens clinical pneumonia, we hypothesise that its use would result in decreased faecal shedding of R. equi by foals. Neonatal foals were either given HIP (n=12) or nothing (n=9, control) shortly after birth and were then experimentally infected with R. equi Faeces were collected before and on weeks 2, 3, 5 and 7 after infection. Presence of virulent R. equi was tested using qPCR. There was strong evidence of an association between HIP administration and a decrease in faecal shedding of virulent R. equi (P=0.031 by Pearson chi-squared test). Foals in the control shed significantly more R. equi (colony-forming units/ml) than foals that received HIP (P=0.008 by Mann-Whitney rank-sum test). While our study is the first to report this additional benefit of HIP administration, future studies are needed to evaluate the implications of its use under field conditions.

Use of non-contrast-enhanced computed tomography to identify deep digital flexor tendinopathy in horses with lameness: 28 cases (2014-2016).

OBJECTIVE: To describe the use of non-contrast-enhanced CT to identify deep digital flexor (DDF) tendinopathy in horses with lameness attributed to pain in regions distal to the metatarsophalangeal or metacarpophalangeal joints. DESIGN: Retrospective case series. ANIMALS: 28 client-owned horses. PROCEDURES: Medical records were searched to identify horses that underwent non-contrast-enhanced CT with or without high-field MRI as part of an evaluation for lameness localized to areas distal to the metacarpophalangeal or metatarsophalangeal joint in ≥ 1 limb. Horses were included in the study if they had ≥ 1 DDF tendon lesion (DDF tendinopathy) identified. Signalment, lameness examination findings and response to perineural anesthesia, imaging modality, anesthetic agents and duration of anesthesia, and imaging findings were recorded. Data were summarized descriptively. RESULTS: Bilateral imaging was performed for all horses, irrespective of unilateral or bilateral lameness. Nine of 28 horses underwent both CT and MRI, and all DDF tendon lesions identified by one modality were identified by the other. Of 48 limbs with DDF tendinopathy, 46 (96%) had core lesions and 35 (73%) had dorsal border irregularities. Median anesthesia time for CT and CT followed by MRI was 15 and 110 minutes, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that non-contrast-enhanced CT was useful for identifying DDF tendinopathy in horses with lameness localized to the phalangeal regions, and this was supported by consistency of findings in a subset of horses that underwent MRI. Further research is needed to confirm these results.

Evaluation of equine coronavirus fecal shedding among hospitalized horses.

BACKGROUND: Currently, diagnosis of equine coronavirus (ECoV) relies on the exclusion of other infectious causes of enteric disease along with molecular detection of ECoV in feces or tissue. Although this approach is complete, it is costly and may not always be achievable. OBJECTIVE: We hypothesized that the overall fecal shedding of ECoV in hospitalized horses is low. Our objective was to determine whether systemically healthy horses and horses with gastrointestinal disorders shed ECoV in their feces at the time of admission to a referral hospital and after 48 hours of stress associated with hospitalization. ANIMALS: One-hundred thirty adult horses admitted to the Washington State University Veterinary Teaching Hospital for gastrointestinal disease (n = 65) or for imaging under anesthesia (n = 65) that were hospitalized for 48 hours. Owner consent was obtained before sampling. METHODS: Fecal samples were collected at admission and 48 hours later. Polymerase chain reaction (PCR) for ECoV and electron microscopy (EM) were performed on all samples. RESULTS: Only 1 of 258 fecal samples was PCR-positive for ECoV. Electron microscopy identified ECoV-like particles in 9 of 258 samples, parvovirus-like particles in 4 of 258 samples, and rotavirus-like particles in 1 of 258 samples. CONCLUSIONS AND CLINICAL IMPORTANCE: The presence of ECoV in feces of hospitalized adult horses was low. Thus, fecal samples that are PCR-positive for ECoV in adult horses that have clinical signs consistent with this viral infection are likely to be of diagnostic relevance. The clinical relevance of the viruses observed using EM remains to be investigated.

Glanzmann thrombasthenia in a 17-year-old Peruvian Paso mare.

A 17-year-old Peruvian Paso mare was evaluated for bilateral epistaxis that had been present for at least 3 years. The mare had mild anemia, platelet count within the reference interval, unremarkable coagulation times, and a negative Coggins test. On endoscopic examination, structural abnormalities were not observed in the nasal cavities, pharynx, larynx, trachea, or either guttural pouch, but petechiation was noted in the nasal mucosa. Additional tests revealed prolonged cutaneous bleeding time, normal concentration of von Willebrand factor antigen, an abnormal clot retraction test, and failure of plalelet aggregation in response to agonists, suggesting a functional disorder of platelets. Genetic analysis indicated the horse was homozygous for a 10-base-pair deletion that included the last 3 base pairs of exon 11 and the first 7 base pairs of intron 11 of the gene encoding glycoprotein IIb. The diagnosis was Glanzmann thrombasthenia (GT) caused by a structural defect in glycoprotein IIb. GT is an autosomal recessive disorder caused by a defect in the glycoprotein IIb-IIIa complex on platelet surfaces. Separate genes encode each glycoprotein, and mutations in either gene can result in GT. This case of GT is unique given the age of the mare at the time of diagnosis. We conclude that GT, although an inherited disorder, should be considered in horses with suspected dysfunctional platelets, regardless of age.

Primary epitheliotropic intestinal T-cell lymphoma as a cause of diarrhea in a horse.

A 25-year-old Appaloosa gelding was evaluated for chronic weight loss and diarrhea. A clinical diagnosis of protein loosing enteropathy was made and the gelding was euthanized. Histology revealed neoplastic lymphocytes infiltrating the mucosa of the small and large intestine. Immunohistochemistry was positive for CD3, consistent with epitheliotropic T-cell lymphoma.

Analgesic effects of butorphanol tartrate and phenylbutazone administered alone and in combination in young horses undergoing routine castration.

OBJECTIVE: To compare the analgesic efficacy of administration of butorphanol tartrate, phenylbutazone, or both drugs in combination in colts undergoing routine castration. DESIGN: Randomized controlled clinical trial. ANIMALS: 36 client-owned colts. PROCEDURES: Horses received treatment with butorphanol alone (0.05 mg/kg [0.023 mg/lb], IM, prior to surgery and then q 4 h for 24 hours), phenylbutazone alone (4.4 mg/kg [2.0 mg/lb], IV, prior to surgery and then 2.2 mg/kg [1.0 mg/lb], PO, q 12 h for 3 days), or butorphanol and phenylbutazone at the aforementioned dosages (12 horses/group). For single-drug-treated horses, appropriate placebos were administered to balance treatment protocols among groups. All horses were anesthetized, and lidocaine hydrochloride was injected into each testis. Physical and physiological variables, plasma cortisol concentration, body weight, and water consumption were assessed before and at intervals after surgery, and induction of and recovery from anesthesia were subjectively characterized. Observers assessed signs of pain by use of a visual analogue scale and a numerical rating scale. RESULTS: Significant changes in gastrointestinal sounds, fecal output, and plasma cortisol concentrations were evident in each treatment group over time, compared with preoperative values. At any time point, assessed variables and signs of pain did not differ significantly among groups, although the duration of recumbency after surgery was longest for the butorphanol-phenylbutazone-treated horses. CONCLUSIONS AND CLINICAL RELEVANCE: With intratesticular injections of lidocaine, administration of butorphanol to anesthetized young horses undergoing routine castration had the same apparent analgesic effect as phenylbutazone treatment. Combined butorphanolphenylbutazone treatment was not apparently superior to either drug used alone.

Fibrinonecrotic enteritis of piglets in a commercial farm: a postmortem study of the prevalence and the role of lesion associated agents Isospora suis and Clostridium perfringens

The objectives were to determine the prevalence of fibrinonecrotic enteritis (FNE) on a farrow-to-finish farm of 1,000 sows, to categorize the pathological changes, and to to investigate the lesion associated agents Isospora suis and Clostridium perfringens. Causes of preweaning mortality (PWM) were classified into 8 categories including FNE. Obtained data were evaluated for statistical significance by adjusted Chi-square analysis. Samples of FNE were taken for complementary studies including a PCR technique for genotyping toxin genes of Clostridium perfringens from gut samples fixed in 10 percent neutral formalin. From 3,153 piglets examined, less than 1 percent was classified as FNE. FNE prevalence increased progressively from the first to the third week, the last differing statistically from the others. Eighty percent of gut samples with FNE lesions were positive to Isospora suis, when examined by PCR from 9 severe FNE lesions detected 7 positive samples only for a toxin gene, characteristic of C. perfringens type-A.

Os objetivos deste trabalho foram determinar a prevalência de enterite fibrinonecrótica (EFN) em uma granja tecnificada com 1000 matrizes, classificar as mudanças patológicas e investigar a lesão decorrente da associação dos agentes Clostri-dium perfringens e Isospora suis. As lesões macroscópicas devidas à mortalidade pré-desmame (MPD) foram classificadas em oito categorias incluindo EFN. Os dados obtidos foram avaliados pelo teste Qui-quadrado. Amostras de EFN foram colhidas para estudos complementares incluindo uma técnica de reação em cadeia da polimerase (PCR) para identificação dos genes codificadores de toxinas de C. perfringens a partir de amostras do intestino fixadas em formalina a 10 por cento. Dos 3.153 leitões examinados, menos que 1 por cento foram classificados como EFN. As análises estatísticas revelaram que a EFN aumentou progressivamente a partir da primeira para a terceira semana, sendo que a última semana diferiu estatisticamente das demais. Oitenta porcento das amostras do intestino com EFN foram positivas para I. suis. Por meio da PCR a partir dos 9 casos de EFN severa, 7 foram positivos somente para o gene da toxina alfa, característico de C. perfringens tipo A.

Detection of an epidermoid cyst in the foot of a horse by use of magnetic resonance imaging.

CASE DESCRIPTION-A 4-year-old Quarter Horse stallion was evaluated because of a 10-month history of moderate (grade 3/5) left forelimb lameness (detectable during trotting over a smooth, hard surface). CLINICAL FINDINGS-No abnormalities were detected in either forelimb via palpation or application of hoof testers; however, lameness was eliminated after administration of a palmar digital nerve block in the left forelimb. Whereas radiography and ultrasonography did not identify any left forelimb foot abnormalities, magnetic resonance (MR) imaging revealed a circumscribed soft tissue mass in the distal aspect of the digital flexor tendon sheath (DFTS) dorsal to the lateral aspect of the deep digital flexor tendon. Subsequently, the left forelimb DFTS was injected with local anesthetic, which resulted in 90% improvement of the horse's lameness. TREATMENT AND OUTCOME-The distal aspect of the left forelimb DFTS was evaluated tenoscopically. The mass was removed under tenoscopic guidance, after which the distal digital annular ligament was transected. The horse received phenylbutazone orally for 10 days, and the left forelimb DFTS was injected with hyaluronic acid and methylprednisolone acetate 7 days after the surgery. Following a rehabilitation program, the horse was returned to full training at 6 months after surgery and competed successfully during a 2-year follow-up period. CLINICAL RELEVANCE-Use of MR imaging should be considered in all lame horses for which a definitive diagnosis cannot be made via radiography, ultrasonography, or other imaging techniques, especially when the lameness has been localized to a specific anatomic region by use of diagnostic anesthesia.