Owner perceptions and experiences with equine necropsy.

In recent years, the number of horses submitted for necropsy has been in decline. This study aimed to identify the perceptions and barriers of equine necropsy through an online survey of horse owners. The data were analyzed by multivariate models for associations and factors that influenced decision making regarding necropsy. The survey yielded 1,366 usable responses. Respondents had higher familiarity with the term "autopsy" compared to "necropsy" (P < 0.001) and showed a greater level of comfort using the terms "body" and "mortality" compared to "carcass" (P < 0.001). Most respondents (82 %) had experienced euthanizing a horse, but few (27 %) were offered a necropsy. Of those offered a necropsy, a majority (81 %) opted to perform one. When asked about their reasons for choosing to have a necropsy performed, recommendations from veterinarians (77.87 OR, 95 % CI: 49.3, 127.5) and already knowing the cause of death (1.85 OR, 95 % CI: 1.2, 30) were positively associated while a benefit to herd health was negatively associated (0.55 OR, 95 % CI: 0.3, 1.0). Owning horses for use as competition animals (1.44 OR, 95 % CI: 0.9, 2.2), the desire for personal closure (1.76 OR, 95 % CI: 1.1, 2.9), and the goals to protect human health (1.29 OR, 95 % CI: 1.0, 1.6) and to improve herd health (1.43 OR, 95 % CI: 1.1, 1.9) were positively associated with a likelihood of choosing to have a necropsy performed or recommending necropsies in the future. This research highlights the need for education of horse owners about the option and benefits of necropsy, and the use of more societally accepted language.

Thrombotic endocarditis in 10 alpacas.

BACKGROUND: A description of the clinical signs and necropsy findings in 10 alpacas with thrombotic endocarditis. ANIMALS: Clinical cases admitted to 2 veterinary referral hospitals between May 1998 and December 2006. METHODS: A retrospective study was performed by searching hospital records to identify alpacas diagnosed with endocarditis. RESULTS: Common clinical findings included sternal recumbency, tachycardia, tachypnea, and abdominal distension. Heart sounds were recorded as normal in 7 of 10 alpacas. Pleural and pericardial effusion and ascites were often present. Complete blood cell counts often suggested inflammation, and liver enzyme activity was often increased. When echocardiography was performed, a soft tissue density was imaged within the right ventricle. All alpacas died or were euthanized. Necropsy revealed mural endocarditis with right ventricular or biventricular fibrinous thrombi obliterating the ventricular lumina with no valvular involvement in 6 of 10 affected animals. Bacteria were not consistently identified as a cause for the endocarditic lesions. Eight of the 10 alpacas had evidence of hepatic fluke infestation. CONCLUSIONS AND CLINICAL IMPORTANCE: Valvular and mural thrombotic endocarditis should be included in the list of differential diagnoses for hepatomegaly, abdominal distension, and other signs of right-sided congestive heart failure in alpacas. The prognosis of this disease is grave.

Factors affecting clinical assessment of insulin sensitivity in horses.

Insulin resistance is thought to be involved in the pathogenesis of many equine conditions such as pars intermedia dysfunction, equine metabolic syndrome, diabetes mellitus, hyperlipaemia, laminitis, endotoxaemia and osteochondrosis dissecans (OCD); whereas polysaccharide storage myopathy in Quarter Horses and equine motor neuron disease (EMD) have been associated with increased insulin sensitivity. However, it is clear that there is not one ideal test, in terms of both practicality and accuracy, for evaluating insulin sensitivity in horses and improved diagnostic techniques are required. This review sets out the background to the subject and identifies current knowledge regarding the measurement of insulin sensitivity by tolerance testing and clamping techniques. Factors affecting insulin sensitivity, such as breed, pregnancy, lactation, obesity and nutritional factors are discussed. In addition, the relationship with training, nutritional supplementation and drug administration are considered.

Posture and movement characteristics of forward and backward walking in horses with shivering and acquired bilateral stringhalt.

REASONS FOR PERFORMING STUDY: To investigate and further characterise posture and movement characteristics during forward and backward walking in horses with shivering and acquired, bilateral stringhalt. OBJECTIVES: To characterise the movement of horses with shivering (also known as shivers) in comparison with control horses and horses with acquired bilateral stringhalt. STUDY DESIGN: Qualitative video analysis of gait in horses. METHODS: Owners' and authors' videos of horses with shivering or stringhalt and control horses walking forwards and backwards and manually lifting their limbs were examined subjectively to characterise hyperflexion, hyperextension and postural abnormalities of the hindlimbs. The pattern and timing of vertical displacement of a hindlimb over one stride unit was evaluated among control, shivering and stringhalt cases. RESULTS: Gait patterns of shivering cases were characterised as follows: shivering-hyperextension (-HE, n = 13), in which horses subjectively showed hyperextension when backing and lifting the limb; shivering-hyperflexion (-HF, n = 27), in which horses showed hindlimb hyperflexion and abduction during backward walking; and shivering-forward hyperflexion (-FHF, n = 4), which resembled shivering-HF but included intermittent hyperflexion and abduction with forward walking. Horses with shivering-HF, shivering-FHF and stringhalt (n = 7) had a prolonged swing phase duration compared with control horses and horses with shivering-HE during backward walking. With the swing phase of forward walking, horses with stringhalt had a rapid ascent to adducted hyperflexion of the hindlimb, compared with a rapid descent of the hindlimb after abducted hyperflexion in horses with shivering-FHF. CONCLUSIONS: Shivering affects backward walking, with either HE or HF of hindlimbs, and can gradually progress to involve intermittent abducted hyperflexion during forward walking. Shivering-HF and shivering-FHF can look remarkably similar to acquired bilateral stringhalt during backward walking; however, stringhalt can be distinguished from shivering-HF by hyperflexion during forward walking and from shivering-FHF by an acute onset of a more consistent, rapidly ascending, hyperflexed, adducted hindlimb gait at a walk.

Epidemiology of shivering (shivers) in horses.

REASONS FOR PERFOMING STUDY: Investigating the epidemiology of shivering in horses. OBJECTIVES: The purpose of this study was to characterise the signalment, clinical signs and management factors associated with shivering (also known as shivers), a relatively rare, poorly defined movement disorder in horses. STUDY DESIGN: Web-based case series survey and case-control study. METHODS: A Web-based survey was used to obtain information from owners, worldwide, who suspected that their horse had shivering. Survey respondents were asked to answer standardised questions and to provide a video of the horse. Authors reviewed the surveys and videos, and horses were diagnosed with shivering if they displayed normal forward walking, with difficulty during manual lifting of the hoof and backward walking due to hyperflexion or hyperextension of the pelvic limbs. Cases confirmed by video were designated 'confirmed shivering', while those with compatible clinical signs but lacking video confirmation were designated 'suspected shivering'. Owners of confirmed shivering horses were asked to provide information on 2 horses without signs of shivering (control group). RESULTS: Three hundred and five surveys and 70 videos were received; 27 horses were confirmed shivering (50 controls), 67 were suspected shivering and the rest had a variety of other movement disorders. Suspected shivering horses resembled confirmed shivering cases, except that the suspected shivering group contained fewer draught breeds and fewer horses with exercise intolerance. Confirmed shivering signs often began at <5 years of age and progressed in 74% of cases. Owner-reported additional clinical signs in confirmed cases included muscle twitching (85%), muscle atrophy (44%), reduced strength (33%) and exercise intolerance (33%). Shivering horses were significantly taller (confirmed shivering, mean ∼173 cm; control horses, ∼163 cm) with a higher male:female ratio (confirmed shivering, 3.2:1 vs. control, 1.7:1). No potential triggering factors or effective treatments were reported. CONCLUSIONS: Shivering is a chronic, often gradually progressive movement disorder that usually begins before 7 years of age and has a higher prevalence in tall male horses.

Effect of feed restriction on plasma dantrolene concentrations in horses.

REASONS FOR PERFORMING STUDY: Dantrolene sodium is used to prevent exertional rhabdomyolysis in predisposed horses. Food intake might negatively impact dantrolene bioavailability in horses; however, prolonged feed restriction might be detrimental to performance. OBJECTIVE: To determine a minimum duration of feed restriction that would optimise plasma dantrolene concentrations in horses after nasogastric administration. It was hypothesised that feed restriction for 4, 8 or 12 h before dantrolene administration would result in higher plasma dantrolene concentrations than achieved with no feed restriction before treatment. METHODS: Five healthy horses were randomly rotated through 4 feed restriction periods of 0, 4, 8 and 12 h duration prior to nasogastric administration of dantrolene sodium (6 mg/kg bwt). Plasma dantrolene concentration was measured by spectrofluorometry at 60, 90, 120, 150, 180 and 210 min after administration. Data were analysed via repeated measures ANOVA. RESULTS: Peak plasma dantrolene concentration was highest when horses had 0 and 4 h of feed restriction (0.65 ± 0.10 µg/ml at 120 min; 0.66 ± 0.17 at 180 min, respectively) and was lower when horses were restricted from feed for 8 h (0.45 ± 0.15 at 150 min) and 12 h (0.21 ± 0.09 at 180 min). Mean plasma dantrolene concentration did not differ between 0 and 4 h feed restriction at any sample time, but feed restriction for 8 h resulted in significantly lower plasma dantrolene concentration at 60 and 180 min after treatment than when horses were restricted 0 and 4 h, respectively. Plasma dantrolene concentration was significantly lower at all sample times when horses were restricted from feed 12 h compared to 0 or 4 h. CONCLUSIONS: Absorption of nasogastrically administered dantrolene is inhibited by feed restriction before administration. To achieve optimal plasma dantrolene concentrations, feed restriction before oral administration should not exceed 4 h.

Comparison of histopathologic criteria and skeletal muscle fixation techniques for the diagnosis of polysaccharide storage myopathy in horses.

The purpose of the study reported here was to determine the effect of three methods of fixation of skeletal muscle biopsy specimens on the histopathologic appearance of muscle sections and to determine criteria that were most consistently associated with a diagnosis of polysaccharide storage myopathy (PSSM) in horses. Surgically excised semimembranosus muscle biopsy specimens were obtained from nine horses previously diagnosed with PSSM and from 15 control horses. Portions of each specimen were fixed in formalin, frozen immediately, and chilled for 24 hours prior to freezing. Sections stained with hematoxylin and eosin (HE), periodic acid-Schiff (PAS), and amylase-PAS were scored for histopathologic criteria by three investigators blinded to the sample origin. The presence of amylase-resistant, abnormal polysaccharide was found to be the most sensitive and specific diagnostic indicator for PSSM, and was readily detected regardless of the fixation technique or investigator. Other less-specific features associated with PSSM included atrophy and cytoplasmic and subsarcolemmal vacuoles; however, their histologic scores varied among fixation technique and investigators. Scores for subsarcolemmal and cytoplasmic amylase-sensitive glycogen in horses with PSSM were similar to those for control horses and varied among fixation techniques. In conclusion, PSSM is most accurately diagnosed in muscle biopsy specimens on the basis of appearance of amylase-resistant, abnormal polysaccharide, not amylase-sensitive glycogen, regardless of fixation technique. In general, frozen sections appeared to be better suited for studying myopathies because many histopathologic features of skeletal muscle were obscured by formalin fixation.