The association between oral examination findings and computed tomographic appearance of the equine temporomandibular joint.

BACKGROUND: The temporomandibular joint (TMJ) forms the junction between the maxilla and mandible. Movement of the jaw and resulting masticatory forces have been extensively studied in the horse; however, less is known about the inter-relationship between this joint and oral and dental pathology. OBJECTIVES: To determine the association between specific oral and dental pathologies and anatomical variations of the TMJ imaged with computed tomography (CT) in horses with asymptomatic TMJs. STUDY DESIGN: Retrospective cross-sectional study. METHODS: Horses (n = 201) from three practices with a complete oral examination and skull or upper cervical CT study were reviewed. Age, breed, sex, clinical presentation, oral examination findings, slice width and practice were recorded. Alterations in contour and density of the mandibular condyle, mandibular fossa and intra-articular disc were also documented. Logistic regression, corrected for clustering by practice, was used to determine whether CT anatomical variations were significantly associated with the oral examination findings. RESULTS: Horses categorised as having abnormal TMJs were older than those with normal TMJ. Horses with periodontal disease were less likely to have abnormal TMJ findings compared with horses with no oral pathology. In contrast, horses with infundibular disease were more likely to have TMJ abnormalities. MAIN LIMITATIONS: Due to the cross-sectional nature of the study, it was difficult to establish whether oral pathology preceded TMJ abnormalities. CONCLUSIONS: Despite examining over 200 horses of varying ages, the biological significance of the observed associations between oral, or dental disease and anatomically appreciable temporomandibular joint disorders remains uncertain.

The effect of acute unilateral inflammation of the equine temporomandibular joint on the kinematics of mastication.

REASONS FOR PERFORMING STUDY: Diseases of the temporomandibular joint (TMJ) are well reported in man and some domestic animals other than the horse. The pathophysiology of equine TMJ disease and the effects of disease on the kinematics of mastication are unknown. OBJECTIVES: To determine whether transient unilateral inflammation of the equine TMJ results in alterations in the masticatory cycle. STUDY DESIGN: An experimental controlled study utilising 6 horses of various ages with normal dentition. METHODS: Each horse was equipped with an optical motion tracking (kinematic) system. Horses were observed chewing grass hay over 3 min intervals. Regardless of the initial side of the power stroke in the masticatory cycle, lipopolysaccharide (LPS) was injected in the left TMJ in each horse and the horses were reassessed after 6 h. RESULTS: Four horses developed effusion of the injected TMJs; 2 of these also began quidding. All horses injected on the original side of the power stroke switched sides while the 2 injected on the contralateral side did not. All horses developed reduced vertical pitch (vertical opening) of the mandible. Overall, rostrocaudal movement of the mandible did not change; however, the timing of this movement relative to the phase of the masticatory cycle did. Injection with LPS did not affect the amount of lateral movement of the mandible. CONCLUSIONS: Injection of LPS into the TMJ significantly altered the masticatory cycle compared with baseline values representing avoidance behaviour due to inflammation of the joint, despite which the horses continued to eat using the contralateral mandible. Lipopolysaccharide administration also led to quidding and a loss of feed efficiency (in some individuals).

Racing performance in Standardbred trotting horses with proximal palmar/plantar first phalangeal fragments relative to the timing of surgery.

REASONS FOR PERFORMING STUDY: Proximal palmar/plantar osteochondral fragmentation of the first phalanx is a frequent radiographic finding in Standardbred horses. These lesions are routinely removed prior to the onset of a racing career with no evidence to support the timing of this surgical intervention. OBJECTIVES: To determine whether horses racing before surgery slowed as they approached surgery date and whether they speeded up after surgery. To investigate the factors affecting whether a horse raced after surgery and compare the performance of horses that did and did not race before surgery. STUDY DESIGN: A retrospective study using 193 Swedish Standardbred trotters. METHODS: Medical records and radiographs of each horse were examined. Racing data were retrieved from official online records. Generalising estimating equations were used to examine presurgery racing performance and determine whether this differed between horses that raced before surgery and those that had not. Multivariable regression was used to examine career earnings and number of career races. RESULTS: Horses racing before surgery neither slowed as they approached surgery, nor speeded up after surgery. Race speed of horses raced before surgery was not different from those that only raced after surgery. Racing before surgery was not associated with whether horses raced following surgery. Only horses with 3 affected legs had slower race speeds than other horses. No other horse level variables affected race speed, number of career races, career earnings or top speed. CONCLUSIONS: There was no significant difference in race speed between horses that raced before surgery and those that did not. Horses did not slow down prior to surgery. Horses with 3 affected legs ran slower than those with only a single or 2 affected limbs. There was no association between timing of surgery and race speed or career longevity. The potential benefits of surgical intervention should be critically examined.

The effect of blood contamination on equine synovial fluid analysis.

OBJECTIVE: Based on a systemic complete blood count and a synovial fluid sample, to develop a mathematical model enabling the approximation of corrected values for synovial fluid white blood cell (WBC) count, neutrophil percentage, and total protein concentration in samples of synovial fluid that were contaminated by blood. METHODS: Peripheral venous blood and synovial fluid samples were obtained from ten horses. A pooled synovial fluid sample from each horse was separated into 2 mL aliquots, which were subsequently contaminated with a known percentage of autogenous blood (0 to 50% of the synovial fluid volume). A complete blood count, packed cell volume, total protein (TP) concentration, and differential cytological examination were performed in all the synovial fluid and venous blood samples. Regression analysis was used to generate a model to calculate non-contaminated synovial WBC count, TP concentration and synovial neutrophil percentage. Using a further five horses these models were applied in blinded fashion to contaminated synovial fluid samples. Calculated values were compared to non-contaminated measured values. RESULTS: Model results for synovial WBC count and TP concentration were not significantly different from measured values. Calculated neutrophil percentage of synovial fluid WBC was a mean of 6.6% higher than measured values and was significantly different. There was no effect of the severity of contamination (as a percentage of volume) on the ability of the models to predict any of the outcome variables. CLINICAL SIGNIFICANCE: It is possible to calculate non-contaminated synovial fluid WBC and TP values, but not neutrophil percentage, from heavily contaminated samples. Further study would allow for improved prediction, validation and extrapolation to a wider horse population.

Morphology of the occlusal surfaces of premolar and molar teeth as an indicator of age in the horse.

The purpose of this study was to investigate the use of cheek tooth occlusal surface morphology as an indicator of age in the horse using a blinded cross-sectional design. Twenty horses of varying age, breed and sex were used. Horses of known age (foaling date) were euthanized for reasons other than dental disease. Following disarticulation of the head and sectioning of the mandibles, cheek teeth were cleaned using running water and photographs were taken of each arcade. Using a computer-based program, the total surface area of each premolar and molar, the outer enamel ridge perimeter distance, infundibular surface areas and perimeter distances were measured. Further anatomical data were calculated from these measurements and a statistical analysis of the relationship between horse age and cheek tooth occlusal morphology was performed. Results indicated that multiple anatomical regions within the occlusal surface of the equine cheek tooth can be used as an indicator of age. There are important differences between mandibular and maxillary teeth as well as between teeth in the same dental arcade. Horse size is also of significance. The mesial infundibular surface area as a percentage of the total surface area of tooth 111, and the mesiodistal length of 1/2/3/4 09 teeth, most closely approximates age within our mathematical model. Cheek tooth morphological data can be used to predict age in horses that possess all their permanent dentition. In cases in which the age of horses cannot be accurately determined from incisor examination, cheek teeth may be used.

Evaluation of common vaginal tunic ligation during field castration in draught colts.

The objective of this study was to determine if ligation of the common vaginal tunic could prevent or reduce the incidence of omental herniation and eventration in draught colts undergoing routine field castration. It was found that common vaginal tunic ligation, while not completely preventing omental herniation and evisceration, significantly reduced the incidence of these complications and should be considered in those males deemed at increased risk of significant post castration complications.

Suspected white kidney bean (Phaseolus vulgaris) toxicity in horses and cattle.

Thirty-four mixed breed horses from two separate farms showed signs of abdominal discomfort, pyrexia and dehydration after being exposed to a new batch of 14% complete horse feed. A new batch of cattle feed from the same manufacturer resulted in dairy cows showing depression, a drop in milk production and diarrhoea. Examination of both diets revealed the presence of white kidney beans (Phaseolus vulgaris). Inclusion of raw beans of this genus in animal feeds is to be avoided.

Suspect copper toxicity in an alpaca.

An alpaca presented in lateral recumbency and subsequently died. On necropsy examination the liver showed severe, widespread, periacinar hepatocellular necrosis, staining positive to a rhodamine stain for copper. Hepatic copper concentration was elevated. Copper toxicity in the camelid is difficult to diagnose, since the classical hemolytic crisis is not observed.

Hypernatremia in neonatal elk calves: 30 cases (1988-1998).

OBJECTIVE: To characterize hypernatremia in neonatal elk calves, including clinical signs, incidence, physical examination findings, and possible causes. DESIGN: Retrospective case series. ANIMALS: 26 neonatal elk calves were examined; 4 calves were evaluated twice, for a total of 30 examinations. PROCEDURE: Medical records were reviewed for signalment, history, physical examination findings, results of diagnostic tests, and response to treatment. Hypernatremia was defined as serum sodium concentration > 153 mEq/L. RESULTS: Hypernatremia was diagnosed in 14 calves and was significantly associated with diarrhea, high WBC count, high anion gap, and high serum concentrations of albumin, chloride, creatinine, and urea. Hypernatremia was not significantly associated with survival, but high serum albumin concentration and rectal temperature were significantly associated with survival of calves. Animals given antibiotics and electrolyte solutions orally prior to evaluation were significantly more likely to die than those untreated. Dehydration was a common reason for evaluation but was not significantly associated with survival. CONCLUSIONS AND CLINICAL RELEVANCE: Hypernatremia was significantly associated with diarrhea. Treatment of diarrheic elk calves is often the same as that used in bovine calves with diarrhea; however, bovine calves are commonly hypo- or normonatremic. Our experience suggests that treatment protocols used in bovine calves are unsatisfactory for elk calves. The rate at which serum sodium concentration is reduced should be < 1.7 mEq Na/L/h to avoid development of neurologic signs associated with iatrogenically induced cerebral edema.

Actinobacillus lignieresii infection in two horses.

A 10-year-old pregnant Norwegian Fjord horse was examined for gross swelling of the muzzle of 2 years' duration. Examination of biopsy specimens revealed diffuse dermal fibrosis, micropustule formation, and vascular thrombosis; large numbers of Actinobacillus lignieresii were isolated in pure culture. Prolonged treatment with i.v. administration of sodium iodide and oral administration of trimethoprim-sulfamethoxazole caused regression of the swelling and did not induce abortion. A 5-month-old American Paint filly was examined for swelling in the udder region. Bacteriologic culture of purulent material obtained from the left teat revealed A lignieresii. Treatment with oral administration of rifampin and trimethoprim-sulfamethoxazole resulted in complete resolution of clinical signs. To the authors' knowledge, these findings represent the first report of mastitis and chronic nasal cellulitis caused by A lignieresii infection in horses.