Use of a Baerveldt gonioimplant for secondary glaucoma in a horse

This case report describes the surgical placement of a Baerveldt glaucoma shunt in the right eye of a 14‐year‐old Arabian gelding. The glaucomatous right eye was refractory to aggressive medical and repeated surgical therapies yet maintained functional vision. Despite the need for intensive post operative management and continued daily topical therapy, shunt placement surgery was successful at maintaining normotension and vision for a period of 402 days. This is the first report of long‐term successful glaucoma filtration surgery in this species. Further studies are warranted to evaluate long‐term success of glaucoma shunt placement in equine glaucoma cases.     

Otitis media/interna and suppurative meningoencephalomyelitis associated with Listeria monocytogenes infection in a llama

Listeria monocytogenes was found to be the cause of fatal suppurative meningoencephalomyelitis in a 3.5-month-old cria. The cria initially had clinical signs of unilateral peripheral vestibular disease, but on the following day, the cria developed progressive signs of encephalitis. Treatment with antibiotics, flunixin meglumine, and anticonvulsant drugs failed to stop progression of the disease, and the cria was euthanatized. Post-mortem examination revealed otitis media-interna and diffuse suppurative meningoencephalomyelitis. Listeria monocytogenes was isolated from CSF and brain tissue.     

Nonulcerative bullous keratitis associated with Pseudomonas alcaligenes infection in a Thoroughbred mare

A 5‐year‐old Thoroughbred mare presented with an intermittently mildly painful right eye with a nonulcerative corneal opacity of several weeks' duration that had improved with topical steroids but recurred when steroids were withdrawn. Ophthalmic examination demonstrated a focal region of moderate corneal oedema and midstromal corneal infiltrate centrally but no other significant ocular abnormalities, and suggested a diagnosis of immune‐mediated keratitis. Empirical courses of both topical and systemic anti‐inflammatory drugs, both nonsteroidal and steroidal, led to initial improvement but bullous keratopathy developed when corneal oedema became profound. Due to the rapidly progressive nature of the bullous keratopathy combined with poor response to medical therapy, a keratectomy and conjunctival graft were performed under general anaesthesia. Intraoperative corneal culture of the keratectomy site grew Pseudomonas alcaligenes, a common soil and water contaminant. Histopathology of the keratectomy specimen revealed neutrophilic inflammation. Keratectomy and conjunctival graft led to resolution of ocular pain and inflammation, with an acceptable cosmetic and visual outcome. This report describes an unusual case of a nonulcerative Pseudomonas keratitis that responded well to surgical therapy, and underscores the complicated nature of nonulcerative keratitis in horses.     

Laparoscopic‐assisted splenectomy in a horse with splenomegaly

This reports describes the surgical management of a horse evaluated for recurrent colic. These frequent colic episodes were attributed by exclusion to an abnormally enlarged spleen (idiopathic splenomegaly). Splenectomy was elected and performed with a laparoscopic assisted technique. The advantages observed by using this surgical approach were a clear view of the visceral aspect of the spleen and consequently an accurate dissection of the hilus of the spleen and associated vasculature. Ultimately the laparoscopic technique allowed the surgeons to reduce the size of the laparotomy incision required to remove the spleen and the overall invasiveness of the procedure. The horse recovered well from the procedure and ultimately returned to the previous level of competitiveness.     

Pseudo‐polydactyly in a horse

A 14‐month‐old half‐breed horse showed a severe lameness due to a lesion of the right forefoot which appeared completely and asymmetrically cleaved, from the solar margin to the coronary band. The horse was presented to an abattoir for slaughter and both forelimbs were collected for diagnostic investigations. The hoof lesion described herein does not fulfil the diagnostic criteria of equine polydactyly since post mortem imaging and pathological investigations ruled out the presence of supernumerary digits. Based on the clinical signs, diagnostic imaging (computed tomography) and gross examination, a diagnosis of pseudo‐polydactyly was proposed. To the best of our knowledge, the features of the present case report are unique, thus widening the range of lesions observed at the level of the hoof, which is crucial for horse health and activity.     

Dysautonomia in a six‐year‐old mule in the United States

Equine dysautonomia, also known as equine grass sickness (EGS), is a well documented disease in several countries. To the authors’ knowledge, EGS has not been reported previously in North America. This report describes EGS in a 6‐year‐old female mule in the USA. Failure initially to consider EGS resulted in a delayed diagnosis. EGS should be considered as a differential diagnosis and appropriate diagnostic tests performed in similar cases in North America.     

Storage‐associated artefact in equine muscle biopsy samples

Reasons for performing study: Muscle biopsy is increasingly used in equine veterinary practice for investigating exertional, inflammatory or immune mediated myopathies and unexplained muscle atrophy. Although formalin‐fixed samples are often used, for complete evaluation, fresh‐frozen tissue is required. Freezing muscle in veterinary practice is impractical: samples sent to specialist laboratories for processing are therefore susceptible to delays, potentially leading to artefact and compromising histological interpretation. Hypothesis: Altered temperature, duration and hydration status influence the severity of storage‐induced artefact in equine muscle. Methods: Skeletal muscle obtained immediately post euthanasia was divided into 6 independent samples from each of 8 horses. One sample per horse was frozen immediately in isopentane precooled in liquid nitrogen. Additional samples were stored in conditions designed to mimic possible situations encountered in practice, including increased storage times, temperature and hydration status. Following storage, stored samples were frozen as before. Cryosections were stained using haematoxylin and eosin and ranked for artefact on 2 occasions by 2 blinded observers. The best samples were processed subsequently with a panel of routine stains and immunolabelled for collagen V to enable the measurement of minimum fibre diameters. Results: Both prolonged storage and increased hydration resulted in more storage‐associated artefact. Samples stored for 24 h chilled on dry gauze were ranked higher than those stored on damp gauze; however, a panel of routinely‐used histochemical staining techniques was unaffected by chilled 24 h storage. There was no significant effect of storage on mean fibre diameter; however, both chilled dry and damp storage for 24 h caused a significant increase in fibre‐size variability. Conclusion and potential relevance: Caution should be exercised when interpreting fibre size profiles in shipped samples. Equine muscle biopsy samples are optimally shipped in dry gauze, sealed in plastic containers and shipped on ice packs to be processed within 24 h and can thus be interpreted by the receiving laboratory with minimal artefact.     

Nd:YAG laser‐assisted transendoscopic procedure for treatment of otitis media in a horse

An 8‐year‐old Warmblood gelding was referred for evaluation of headshaking to the Clinic for Horses, University of Veterinary Medicine Hannover. Based on clinical signs and computed tomography – as well as magnetic resonance imaging – findings, otitis media was diagnosed. Medical treatment including trimethoprim potentiated sulfadimethoxine and meloxicam for 3 weeks did not result in cessation of clinical signs. Therefore, the tympanic cavity was opened transendoscopically using an Nd:YAG‐laser via the guttural pouch according to surgical procedures in human and small animal medicine, leading to a considerable improvement of clinical signs.     

Multinodular pulmonary fibrosis,pancytopenia and equine herpesvirus‐5 infection in a Thoroughbred gelding

A 21‐year‐old Thoroughbred gelding was examined for intermittent fever, lethargy, inappetance and weight loss. Initial diagnostic evaluation revealed pancytopenia (anaemia, thrombocytopenia and neutropenia), hyperfibrinogenaemia and multifocal pulmonary nodules. Bacterial and fungal culture and viral isolation on transtracheal aspirate samples were negative, consistent with either pulmonary neoplasia, idiopathic granulomatous pneumonia or equine multinodular pulmonary fibrosis (EMPF). Bone marrow evaluation was consistent with pancytopenia due to a combination of peripheral consumption/destruction and suppression/destruction of progenitor cells at the level of the marrow. Pancytopenia resolved and clinical signs improved transiently with immunosuppressive corticosteroid therapy, but the horse deteriorated rapidly one month after presentation and was subjected to euthanasia. Necropsy findings were consistent with EMPF, and equine herpesvirus‐5 (EHV‐5) DNA was found in both the lung and bone marrow. The specific role of EHV‐5 in the development of the pulmonary pathology in EMPF and the pancytopenia in this horse is unclear, but an aberrant host immune/inflammatory response to EHV‐5 infection may be important.     

Diagnosis of Borrelia‐associated uveitis in two horses

Borrelia burgdorferi, the etiologic agent of Lyme disease is a tick born spirochetal infection. Clinical signs of Lyme borreliosis are uncommon in horses, but when present they are often vague and nonspecific. In horses, Lyme borreliosis has been implicated in musculoskeletal, neurological, reproductive, and ocular disorders, including uveitis, but definitive diagnosis can be challenging as the causative agent is rarely isolated and serologic tests can be unreliable and do not confirm active disease. Here, we report two cases of equine uveitis associated with B. burgdorferi based on the identification of spirochetes within ocular fluids and confirmed with PCR testing. The two cases illustrate some of the challenges encountered in the recognition and diagnosis of equine Lyme borreliosis. Although only one of many possible causes of equine uveitis, Lyme disease should be considered a differential diagnosis, especially in endemic areas. Given the possibility for false negative results of serum tests during uveitis associated with B. burgdorferi and the failure of such tests to confirm active infection, a combination of cytologic assessment, antibody, and/or PCR testing of ocular fluids may be worthwhile if the clinical suspicion for Lyme uveitis is high.     

Extreme lymphocytosis with myelomonocytic morphology in a horse with diffuse large B‐cell lymphoma

An 11‐year‐old, 443‐kg Haflinger mare was presented to the North Carolina State University Veterinary Teaching Hospital with a 2‐week history of lethargy and a 3‐day duration of anorexia, pyrexia, tachycardia, and ventral edema. Severe pitting edema, peripheral lymphadenopathy, and a caudal abdominal mass were noted on physical examination. An extreme leukocytosis (154.3 × 10³/μL) and microscopic hematologic findings suggestive of myelomonocytic leukemia were observed. Serum protein electrophoresis revealed a monoclonal gammopathy and urine protein electrophoresis revealed a monoclonal light chain proteinuria. Necropsy and histopathology confirmed widespread neoplastic infiltration in many organs with a heterogenous population of cells; there was no apparent evidence of bone marrow involvement. Immunohistochemistry confirmed presence of a majority of B cells with a limited antigen expression, admixed with a lower number of T cells. Molecular clonality analysis of IgH2, IgH3, and kappa‐deleting element (KDE, B cell) on whole blood and KDE on infiltrated tissues revealed clonal rearrangements, and the KDE intron clones that amplified in blood and in infiltrated tissue were identical. In contrast, the clonality analysis of T‐cell receptor γ revealed no clonality on blood cells and infiltrated tissues. In conjunction with the histopathologic changes, the lesion was interpreted to be composed of neoplastic B cells with a reactive T‐cell population. Polymerase chain reaction testing for equine herpes virus 5 was negative. The final diagnosis was diffuse large B‐cell lymphoma with a marked hematogenous component.     

Self‐inflicted lingual trauma secondary to inferior alveolar nerve block in 3 horses

Exodontia is the typical treatment recommended in severe cases of dental disease where alternative treatment techniques fail to salvage the affected tooth. Exodontias are frequently performed in the standing horse with the benefit of sedation and regional anaesthesia in order to avoid the risks and expense of general anaesthesia. The inferior alveolar nerve block is commonly utilised when extracting diseased mandibular dentition. Because of the close anatomical relationship of the lingual and inferior alveolar nerves both may be desensitised following anaesthesia of the inferior alveolar nerve. Desensitisation of the tongue may result in horses traumatising it during mastication before sensation returns. This report describes 3 horses that sustained self‐inflicted lingual trauma following inferior alveolar nerve blocks performed for standing oral surgical procedures.     

Hyperkalaemic periodic paralysis‐like syndrome in a Criollo Argentino horse

Hyperkalaemic periodic paralysis (HYPP) is a relatively new genetic disease that, so far, appears to be confined to descendants of the American Quarter Horse Impressive, a stallion identified as the link between the pedigrees of all affected horses, and that predominantly affects Quarter Horses but also Paint horses, Appaloosas and Palominos. This study suggests that an episode of muscle weakness, which was reported in a Criollo Argentino genetically unrelated to Impressive, was related to marked hyperkalaemia. The symptoms in this case were reproducible following a KCI challenge test although DNA testing for HYPP was negative. Based on these findings, a diagnosis of a HYPP‐like syndrome was made.     

True cementomas (cementoblastomas) associated with a nonvital left maxillary second premolar in an 11‐year‐old miniature horse

An 11‐year‐old miniature horse gelding presented for a left maxillary facial swelling and surgical removal of 2 ovoid mineralised masses located near the tooth roots of the left maxillary second and third premolars. Preoperative radiographs were performed to triangulate the location of the calcified masses for removal, and an oral examination revealed that the left maxillary second premolar was nonvital with multiple feed‐packed pulp exposures. Both the radiographs and oral examination indicated that the mineralised masses were associated with the nonvital second premolar. Therefore, the tooth was extracted intraorally, and the masses were removed via a maxillary trephine dorsal to the extracted tooth. Both masses were submitted for histopathology, which diagnosed the masses as true cementomas (cementoblastomas) with adenomatous hyperplasia of the surrounding nasal glandular tissue.     

Epidemiological features and association with crib‐biting in horses with neurological disease associated with temporohyoid osteoarthropathy (1991–2008)

A retrospective study of 43 cases of temporohyoid osteoarthropathy was performed to evaluate the epidemiological features and a possible association with crib‐biting. Data collected from records included case details, what diagnostics were utilised, whether medical or surgical treatment was administered, and outcome. Owners were contacted via telephone and asked whether the horse had displayed crib‐biting behaviour. Forty‐three horses were diagnosed with neurological disease associated with temporohyoid osteoarthropathy, 62.8% of which were Quarter Horse‐types. Median age at presentation was 10 years and median duration of neurological signs prior to presentation was 3 days. Skull radiographs and guttural pouch endoscopy were used to definitively diagnose temporohyoid osteoarthropathy in 72% of the cases. Of 43 horses, 21 received medical treatment and 15 surgical treatment, with an overall survival rate of 55.8%. Crib‐biting was observed in 31.3% of cases and there was a significant association between being afflicted with THO and likelihood of possessing the behaviour. Horses with neurological disease associated with THO were 8 times more likely to be crib‐biters compared to the general population.