Common and atypical presentations of Anaplasma phagocytophilum infection in equids with emphasis on neurologic and muscle disease.

BACKGROUND: Comprehensive descriptions of equids with granulocytic anaplasmosis (EGA) with neurologic or muscle disease and other atypical presentations are scarce in the literature. OBJECTIVE: Describe the clinical signs, laboratory findings, treatment, and outcome of equids with EGA with emphasis on neurologic and muscle disease. ANIMALS: Thirty-eight horses, 1 donkey. METHODS: Retrospective study. Equids with EGA were included. The electronic data base was searched from January 2000 to December 2022 using the words anaplasmosis, ehrlichiosis, granulocytic, and rickettsia. Signalment and clinical data were reviewed. Data were evaluated for normality using Shapiro-Wilk test. Parametric and nonparametric statistics were used for normally and non-normally distributed data. RESULTS: Common (41%) and other (59%) presentations were seen in horses ≥ 4 years of age (median, 14 years) with an overrepresentation of males (77%). Neurologic disease was common (41%), mainly presenting as diffuse symmetrical proprioceptive ataxia. Brain disease was less common manifesting as obtundation and cranial nerve deficits. Muscle disease was less common, with QH breeds with the variant causing myosin heavy chain myopathy (MYHM) having severe disease. Cavitary effusion, cardiomyopathy and disseminated intravascular coagulation (DIC) were uncommon. Clinical laboratory results varied depending on disease stage. Muscle enzyme activities were significantly higher in horses with muscle disease. Outcome was favorable with prompt tetracycline treatment. Death and long-term sequelae were not reported. CONCLUSIONS AND CLINICAL IMPORTANCE: Common and atypical presentations of EGA have a favorable outcome with prompt tetracycline treatment. Quarter horse breeds with muscle disease should be genotyped for MYHM.

Equine Gunshot Euthanasia: Creation of a 3D-Printed Model with Integrated Sensors for Training.

Challenges and issues related to the use of pentobarbital euthanasia and disposal of animal remains within the US have recently been reviewed. Environmental and public health challenges increasingly necessitate consideration of alternative methods such as gunshots, an American Veterinary Medical Association (AVMA) "acceptable with conditions" method, for the humane euthanasia of horses. A recent study reported a correctly aimed gunshot provides a humane option for euthanizing horses. However, although aiming guidelines exist, studies examining bullet trajectories in animals euthanized by gunshot have reported that inadequate disruption of the brain is a serious welfare issue. Here, we report the development and production of a portable, reusable, equine gunshot euthanasia training model. Using 3D printing, an anatomically accurate model of an equine head has been developed, with external aiming landmarks and equipped with integrated laser sensors and LED eyes. The laser sensors are embedded in two specific anatomical tracts (pons and medulla) with aiming paths associated with the aiming landmarks to train correct aiming angle. The LED eyes are linked to the laser sensors to provide instant feedback on aiming accuracy. When a beam from a commercially available blue training gun laser travels along the correct aiming path and strikes the sensor inside the head, the lights in the model's eyes go out and there is an audible signal, providing immediate feedback on the accuracy of the shot. The model facilitates the training of veterinary personnel and first responders in successful gunshot euthanasia, providing instantaneous feedback on the likelihood of a shot causing immediate, humane death in a live animal.

Fish evacuation and emergency sheltering during wildfire disasters.

Wildfires are a serious and expanding threat in western North America, and wildfire encroachment on human populations leads to widespread evacuation and emergency housing operations for residents and their companion animals and livestock. Veterinarians are frequently part of wildfire response efforts and are called upon to assist in rescue, evacuation, and emergency housing operations as well as to provide medical care for evacuated animals. Although veterinarians are likely familiar with the principles of transporting and housing terrestrial animals, emergency response for aquatic companion animals presents unique logistic challenges. Veterinarians familiar with aquatic animal evacuation, housing, and care prior to a wildfire response can extend the scope of disaster recovery. This report offers general guidance for rescuing, evacuating, housing, and caring for aquatic animals in the wake of a wildfire.

Validation of the Alpha Defensin Lateral Flow Test for Periprosthetic Joint Infection.

BACKGROUND: The synovial fluid test for alpha defensin has been reported to have an excellent performance in diagnosing periprosthetic joint infection (PJI). The purpose of this study was to evaluate the performance of the lateral flow test for synovial fluid alpha defensin by using the methods of a formal diagnostic accuracy study and to compare its performance with that of the laboratory-based alpha defensin test for PJI. METHODS: We conducted a diagnostic accuracy study of the index lateral flow immunoassay for synovial fluid alpha defensin relative to the reference 2013 Musculoskeletal Infection Society (MSIS) multicriteria definition of PJI. The study included a prospective multicenter cohort of outpatients with a failed hip or knee arthroplasty and a supplemental control cohort of fresh synovial fluid specimens submitted by physicians for diagnostic PJI testing. RESULTS: Among 57 patients with PJI and 248 patients without PJI in the overall prospective patient cohort, the sensitivity and specificity of the alpha defensin lateral flow test were 89.5% (95% confidence interval [CI]: 78.5% to 96.0%) and 94.8% (95% CI: 91.2% to 97.2%), respectively. The sensitivity increased to 94.3% (95% CI: 84.3% to 98.8%) after exclusion of 17 patients with grossly bloody aspirates (>1 million red blood cells/µL). Among the supplemental control cohort of fresh synovial fluid samples, including 65 samples from patients with PJI and 397 from patients without PJI, the sensitivity and specificity of the alpha defensin lateral flow test were 98.5% (95% CI: 91.7% to 100.0%) and 98.2% (95% CI: 96.4% to 99.3%), respectively. A comparison of the sensitivity and specificity of the alpha defensin lateral flow test with those of the alpha defensin enzyme-linked immunosorbent assay (ELISA) in the combined cohort did not demonstrate a significant difference in sensitivity (94.3% [95% CI: 88.5% to 97.7%] compared with 93.0% [95% CI: 87.1% to 96.7%]) or specificity (96.9% [95% CI: 95.3% to 98.1%] compared with 97.8% [95% CI: 96.4% to 98.8%]) (both p > 0.05). CONCLUSIONS: The results of this study demonstrate the solid diagnostic performance of the alpha defensin test and have resulted in the U.S. Food and Drug Administration (FDA) authorization of the lateral-flow test with an intended use as an aid in the clinical diagnosis of PJI. LEVEL OF EVIDENCE: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Steroid precursors, steroids, neuroactive steroids, and neurosteroids concentrations in serum and saliva of healthy neonatal heifer Holstein calves.

BACKGROUND: Persistence of high neurosteroid concentrations in blood is associated with neonatal encephalopathy and septicemia in foals. This has not been investigated in calves. OBJECTIVES: To determine concentrations of steroid compounds in serum and saliva within the first 48 hours after birth in healthy neonatal calves, identify potential markers for disease, and investigate the association between serum steroid compounds concentrations in calves and their respective dams within 2 hours after birth. ANIMALS: Twelve healthy neonatal heifer Holstein calves and their dams. METHODS: Prospective study. Serum and saliva were collected from calves at 2, 6, 24, and 48 hours after birth. Steroid compounds were analyzed using liquid chromatography-mass spectrometry. A nonlinear regression model was used to determine half-lives of the neurosteroids. Serum concentrations of neurosteroids between the cows and calves were compared using the Wilcoxon signed rank test. RESULTS: Half-lives (95% confidence intervals) of dehydroepiandrosterone (DHEA) and 17α,20α-dihydroxyprogesterone in calf serum were 2.9 (2.1, 4.3), and 2.1 (1.3, 3.0) hours, respectively. Pregnanediol in saliva had a half-life (95% confidence interval) of 24.5 (14.2, 66.5) hours. Serum DHEA (1718.7 ± 2313 vs 57.7 ± 44) and 17α,20α-dihydroxyprogesterone (207.8 ± 198.2 vs 43.5 ± 33.5) concentrations respectively were higher (P < .05) in calves compared to cows. CONCLUSIONS AND CLINICAL IMPORTANCE: Dehydroepiandrosterone, 17α,20α-dihydroxyprogesterone, and pregnanediol could be potential markers of disease in neonatal heifer calves with unexplained failure to thrive or encephalopathy. However, because of the wide 95% confidence interval of the half-life, pregnanediol in saliva might not be a potential marker.

Current Operational Model for Veterinary Care in Large Animal Shelters During Disasters.

Standardization of operating guidelines for veterinary care in evacuation and emergency animal shelters is imperative for an organized response and to facilitate treatment and prevention of medical conditions stemming from the effects of a disaster and the associated outcomes of sheltering. Safeguarding animal welfare through creating guidelines should expedite care, assure consistency, and provide appropriate safety measures for animals and veterinary medical providers. Veterinary integration into an incident command system (ICS) and response training allows for proper allocation of roles and responsibilities, as well as coordination of veterinary supplies and personnel. Central components of the operational model include guidelines for animal identification, triage, medical records, medical treatments, and discharge instructions. An outline for communication with disaster response agencies, as well as animal owners, is aimed to inform appropriate conduct. Improving the animal component of disaster response is integral in meeting societal needs and improving animal welfare in the face of a disaster.

Disaster Medicine: Implementation of an animal health database in response to the 2018 California Camp Fire.

OBJECTIVE: To describe an animal health database used to facilitate effective disaster response and retrospective analysis of data concerning animals other than cats and dogs affected by the 2018 California Camp Fire. ANIMALS: Veterinary medical entries (n = 206) for evacuated or rescued animals (151) of various species, including avian, bovine, camelid, caprine, equine, ovine, and porcine species, temporarily housed at the Butte County fairgrounds in Gridley, Calif. PROCEDURES: Case data were collected via a standardized form by volunteers with the University of California-Davis Veterinary Emergency Response Team during triage and treatment of animals brought to the shelter. Collected data were entered into a database. Multiple correspondence analysis was used to evaluate associations among patient species, types and severity of injuries, and behavior. RESULTS: Burns, respiratory disease, gastrointestinal illnesses, and lacerations were the most prevalent illnesses and injuries among the overall shelter population for the first 12 days of the Camp Fire. Ovine patients were more likely to have had respiratory illness than were other species. The most prevalent medical conditions among equine patients were lacerations and gastrointestinal illnesses. Severe burns were most common among porcine, camelid, and avian patients. The temporal distribution of cases suggested the immediate evacuation of equine species and the delayed movement of bovine and avian species to the shelter. CONCLUSIONS AND CLINICAL RELEVANCE: Collection of animal health information through the database allowed assessment of prevalent medical conditions among various farm animals following a wildfire. Adaptation of this database to other disasters could improve emergency response protocols by providing guidance for management of resources and allow retrospective assessment for response improvement.

Plasma concentrations of steroid precursors, steroids, neuroactive steroids, and neurosteroids in healthy neonatal foals from birth to 7 days of age.

BACKGROUND: Transient hypothalamic-pituitary-adrenal axis dysfunction occurs in critically ill foals with sepsis and neonatal maladjustment syndrome (NMS). Cortisol is the most commonly measured steroid. However, a complex interaction of various steroid compounds might play a role in pathophysiology of this disorder. OBJECTIVE: To identify steroid compounds present at high concentrations at birth that rapidly and steadily decrease within the first 7 days of life in healthy foals and that might be supportive diagnosis of NMS and other neonatal disorders. ANIMALS: Ten healthy neonatal Quarter Horse foals (5 females and 5 males). METHODS: Prospective study. Blood was collected in heparinized tubes within 30 minutes after birth, and at 12, 24, 48, 72, 96, 120, 144, and 168 hours of age. Plasma was separated and a panel of steroid compounds was analyzed using liquid chromatography-mass spectrometry. A nonlinear regression model was used to determine decay concentrations over time. Confidence intervals (CIs) were calculated and significance was set a P ≤ .05. RESULTS: Five compounds were identified: pregnenolone, progesterone, deoxycorticosterone, dehydroepiandrosterone, and dehydroepiandrosterone sulfate. Pregnenolone and progesterone concentrations rapidly decreased by 24 hours of age and remained low throughout the first 7 days of life. Their half-life (95% CI) was short at 3.7 (3.4, 4.0) and 4.5 (2.8, 6.1) hours, respectively. No statistical differences in the concentrations of these compounds were found between males and females. CONCLUSIONS AND CLINICAL RELEVANCE: Progesterone might be a useful marker for identifying continuous endogenous production of neuroactive steroids in foals with suspected NMS and other neonatal diseases.

Description of Placement Procedures for Common Methods Used in Equine Emergency Rescue Using a Simplified Loops System.

Entrapped, stranded and recumbent equids often require emergency rescue. The success of the rescue is often affected by secondary injuries from struggling of the horse to rise and from injury secondary to attempted rescue by pulling on the head or limbs of the equid. Therefore, having ready access to simplified rescue equipment which can be easily applied would be desirable. The devices currently available for these manipulations are not always readily available at the site of an incident. Here, we describe and illustrate the step-by-step use of a Loops System consisting of 183 cm round slings, which can be positioned on the recumbent horse utilizing commercially available and reasonably priced equipment. The Loops System is basically composed of four round slings placed in such a way that utilizes the skeletal system for support. The procedures are illustrated utilizing a recumbent life-size horse model or mannequin. We suggest that the Loops System kit may allow enhanced ability for responders to provide care to a recumbent horse.

Evaluation of a Simplified Loops System for Emergency Rescue Lifting of the Stranded or Recumbent Horse.

Stranded and recumbent equids often require emergency rescue, and a successful rescue often requires vertical lifting of the animal. Currently, the devices used for vertical lifting of equids are not readily available at an incident or urgent situation. The current study describes and evaluates the use of a simple lift device utilizing commercially available, and reasonably priced, equipment. The system, referred to as the Loop Vertical Lift System or Loops System, is basically composed of four round slings placed in such a way that utilizes the skeletal system for support. The study demonstrates the lifting of six standing, sedated adult horses for 3 min without adverse effects. In conclusion, this novel lift system is an affordable, practical and quick alternative to rescue a stranded or recumbent horse that requires a brief vertical lift of the animal. In contrast, for longer-term lifting and support, other devices such as the UC Davis Large Animal Lift, the Anderson Sling Support Device, or the Animal Rescue and Transport Sling (ARTS) should be used as deemed appropriate.

Effects of magnesium with or without boron on headshaking behavior in horses with trigeminal-mediated headshaking.

BACKGROUND: Oral administration of magnesium and boron might have a beneficial effect on headshaking behavior in horses. OBJECTIVE: Evaluate the effects of oral magnesium alone or in combination with boron on headshaking behavior in affected horses. ANIMALS: Twelve geldings (6 healthy controls and 6 affected). METHODS: Prospective randomized controlled dietary trial over 42 days in 12 horses (6 horses diagnosed with trigeminal-mediated headshaking and 6 unaffected healthy controls). All horses received a hay diet and were randomized into 3 treatment groups: pelleted feed combination (PF), pelleted feed combination with magnesium (M), and pelleted feed combination with magnesium-boron (MB) with a week washout of hay only between treatments. Headshaking behavior and biochemical blood variables were assessed at baseline (hay only) and then after each week of supplementation. RESULTS: All 3 diet interventions increased blood ionized and total magnesium. Groups M and MB further increased Mg2+ when compared to PF. Horses receiving treatments had a significant reduction in headshaking behavior, as measured by incidence rate ratio (IRR), when compared to unsupplemented hay diet (44% for PF, IRR, 0.558; CI, 0.44, 0.72; P < .001; 52% for M, IRR, 0.476; CI, 0.37, 0.62; P < .001; and 64% for MB, IRR, 0.358; CI, 0.27, 0.48; P < .001). CONCLUSIONS AND CLINICAL IMPORTANCE: Magnesium in combination with boron had the greatest decrease in headshaking. Oral supplementation with magnesium or magnesium in combination with boron should be considered in horses affected with headshaking.

Luteinizing hormone concentrations in healthy horses and horses with trigeminal-mediated headshaking over an 8-hour period.

BACKGROUND: Trigeminal-mediated headshaking results from a low threshold for firing of the trigeminal nerve. A seasonal component has been implicated in onset of clinical signs, which occur during the spring and summer months. Geldings are overrepresented in the affected population and hormonal differences as compared to a healthy control population of geldings might contribute to headshaking. OBJECTIVE/HYPOTHESIS: To assess concentrations of luteinizing hormone (LH) over an 8-hour period in gelded healthy controls and horses affected with headshaking. Our hypothesis was that geldings with seasonal headshaking would have higher concentrations of LH over an 8-hour period compared to control horses during the summer when affected horses manifested headshaking. ANIMALS: Twelve geldings (6 controls and 6 affected). METHODS: Prospective controlled trial. Blood samples were drawn every 15 minutes over an 8-hour time period during summer from all horses to measure circulating LH concentrations by using a radioimmunoassay for equine LH. All affected horses were actively affected by headshaking at the time of sample collection. RESULTS: No statistically significant differences in LH concentrations were found throughout the study period in headshakers as compared to control horses. Time had no significant effect, but a slight decrease in LH concentrations was observed for all horses. The main limitation of the study was the low number of horses. CONCLUSIONS AND CLINICAL IMPORTANCE: Horses affected with headshaking did not have significant differences in circulating LH during the late summer as compared to control horses.

Intravenous infusion of magnesium sulfate and its effect on horses with trigeminal-mediated headshaking.

BACKGROUND: Trigeminal-mediated headshaking results from low-threshold firing of the trigeminal nerve resulting in apparent facial pain. Magnesium may have neuroprotective effects on nerve firing that potentially dampen signs of neuropathic pain. This hypothesis has not been investigated in horses with trigeminal-mediated headshaking. OBJECTIVE: To investigate head-shaking behavior in affected horses after IV magnesium sulfate infusion. ANIMALS: Six geldings with trigeminal-mediated headshaking. METHODS: Prospective randomized crossover study. Horses were controlled for diet and infused IV with 5% dextrose solution (DS; control solution at 2 mL/kg body weight [BW]) and MgSO4 50% solution (MSS at 40 mg/kg BW). Head-shaking behavior was recorded at times T0 (baseline, before infusion) and T15, T30, T60, and T120 minutes post-infusion. Venous blood variables such as pH, HCO3 - , standard base excess (SBE), Na+ , Cl- , K+ , Ca2+ , Mg2+ , total magnesium (tMg), glucose, and lactate were measured; strong ion difference (SID) and anion gap (AG) were calculated for each time point. RESULTS: Blood variables including pH, Na+ , Cl- , K+ , SID, AG, lactate, Ca2+ , tMg, and Mg2+ had significant changes with MSS as compared to DS treatment. Glucose, SBE, and HCO3 - did not have significant changes. A 29% reduction in head-shaking rate occurred after MSS treatment but no change occurred after DS treatment. CONCLUSIONS AND CLINICAL IMPORTANCE: Administration of MSS IV increased plasma total and ionized magnesium concentrations and significantly decreased head-shaking behavior in horses with trigeminal-mediated headshaking.

Effect of valacyclovir on EHV-5 viral kinetics in horses with equine multinodular pulmonary fibrosis.

BACKGROUND: Equine herpesvirus-5 is commonly isolated from the lungs of horses with EMPF, suggesting an etiological link. Valacyclovir is used empirically to treat EMPF; however, no data is available concerning its impact on EHV-5 viral kinetics. OBJECTIVES: To determine the effect of oral administration of valacyclovir on EHV-5 viral load measured by qPCR in blood, nasal secretions (NS) and BALF in horses with EMPF. ANIMALS: Six horses diagnosed with EMPF. METHODS: A prospective clinical trial was performed. Horses received 10 days of PO administered valacyclovir (loading dose 30 mg/kg, maintenance dose 20 mg/kg). Blood, NS, and BALF were collected for EHV-5 viral kinetics analyses during treatment. Blood and NS were collected every other day. BALF was collected on day 0 and day 10. RESULTS: There was no statistical difference in median EHV-5 viral load between day 0 and day 10 for all samples tested. In blood median EHV-5 viral load was 7676 (range 575-39 781) on day 0 and 6822 (range 1136-18 635) glycoprotein B (gB) gene copies per million cells on day 10. For NS median EHV-5 viral load was 2.944 × 106 (range 184 691-3.394 × 109 ) on day 0 and 8.803 × 106 (range 251 186-9.868 × 108 ) gB gene copies per million cells on day 10. For BALF median EHV-5 viral load was 59,842 (range 61-315 655) on day 0 and 185 083 (range 3562-542 417) gB gene copies per million cells on day 10. CONCLUSIONS AND CLINICAL IMPORTANCE: Valacyclovir might not be an effective short-term antiviral treatment but efficacy in treatment of EMPF is unknown.

Alterations in Metabolic Status and Headshaking Behavior Following Intravenous Administration of Hypertonic Solutions in Horses with Trigeminal-Mediated Headshaking.

Trigeminal-nerve-mediated headshaking represents a major welfare challenge for owners and veterinarians and is caused by a low threshold firing of the trigeminal nerve resulting in pain manifested as violent head jerking that often terminates the horse’s career and life due to poor quality of life and suffering. As metabolic changes such as acid⁻base status and electrolytes play a role in nerve firing, this study sought to assess the effects following administration of hypertonic solutions on headshaking behavior in affected horses. This prospective randomized controlled crossover design utilized six horses affected with trigeminal-mediated headshaking and three treatment groups receiving intravenous administration of 5% dextrose solution at 2 mL/kg bwt (DS), NaCl 7.5% at 4 mL/kg bwt (HS), or NaHCO3 8.4% at 2 mmol/kg bwt (HB). Horses were assessed for headshaking behavior changes at times T0 (baseline, before infusion) and T15, 30, 60, 120 min post infusion. Venous blood variables: pH, HCO3−, standard base excess (SBE), Na⁺, Cl−, K⁺, Ca2+, Mg2+, total magnesium (tMg), glucose, and lactate were measured at T0 (baseline, before infusion) and T5, 15, 30, 60, 120 min post infusion. Strong ion difference (SID) and anion gap (AG) were calculated for each time point. With HB treatment, there was greater than 50% reduction in headshaking rate. There was an effect of time on increasing headshaking rate. There was an effect of breed on headshaking rate. Changes in blood parameters following DS were virtually absent. Infusion of HS caused mild changes and did not vary much from baseline except for SID and AG. Only infusion of HB caused blood pH and HCO3− to be outside of the physiologic range (alkalemia and metabolic alkalosis, respectively), SBE to double or triple, AG to decrease, and SID to increase compared to baseline. Infusion of DS was followed by increase in blood glucose and decrease in blood Na⁺. Infusion of HS was followed by increase in Na⁺ and Cl− and decrease in Mg2+. Infusion of HB was followed by decrease in Mg2+. Blood tMg, K⁺, and Ca2+ decreased slightly, but did not vary greatly from baseline following any of the treatments, remaining within physiologic ranges. Changes in blood composition were transient. Among all treatments, only HB had an effect on headshaking rate. The limited effects following these fluids were likely due to normal mechanisms of regulation of blood levels of pH and electrolytes. Further investigations of changes in electrolytes that might affect nerve firing should be explored.

Survey of Veterinarians Using a Novel Physical Compression Squeeze Procedure in the Management of Neonatal Maladjustment Syndrome in Foals.

Horses are a precocious species that must accomplish several milestones that are critical to survival in the immediate post-birth period for their survival. One essential milestone is the successful transition from the intrauterine unconsciousness to an extrauterine state of consciousness or awareness. This transition involves a complex withdrawal of consciousness inhibitors and an increase in neuroactivating factors that support awareness. This process involves neuroactive hormones as well as inputs related to factors such as cold, visual, olfactory, and auditory stimuli. One factor not previously considered in this birth transition is a yet unreported direct neural reflex response to labor-induced physical compression of the fetus in the birth canal (squeezing). Neonatal maladjustment syndrome (NMS) is a disorder of the newborn foal characterized by altered behavior, low affinity for the mare, poor awareness of the environment, failure to bond to the mother, abnormal sucking, and other neurologically-based abnormalities. This syndrome has been associated with altered events during birth, and was believed to be caused exclusively by hypoxia and ischemia. However, recent findings revealed an association of the NMS syndrome with the persistence of high concentrations of in utero neuromodulating hormones (neurosteroids) in the postnatal period. Anecdotal evidence demonstrated that a novel physical compression (squeeze) method that applies 20 min of sustained pressure to the thorax of some neonatal foals with this syndrome might rapidly hasten recovery. This survey provides information about outcomes and time frames to recovery comparing neonatal foals that were given this squeeze treatment to foals treated with routine medical therapy alone. Results revealed that the squeeze procedure, when applied for 20 min, resulted in a faster full recovery of some foals diagnosed with NMS. The adjunctive use of a non-invasive squeeze method may improve animal welfare by hastening recovery and foal-mare interactions that minimize health problems. This would also avoid or reduce costs arising from hospitalization associated with veterinary and nursing care that sometimes leads owners to elect for euthanasia.

Pharmacokinetics and pharmacodynamics of intravenous romifidine and propranolol administered alone or in combination for equine sedation.

OBJECTIVE: Propranolol has been suggested for anxiolysis in horses, but its sedation efficacy and side effects, both when administered alone and in combination with α2-adrenoceptor agonists, remain undetermined. This study aimed to document the pharmacokinetics and pharmacodynamics of propranolol, romifidine and their combination. STUDY DESIGN: Randomized, crossover study. ANIMALS: Six adult horses weighing 561 ± 48 kg. METHODS: Propranolol (1 mg kg-1; treatment P), romifidine (0.1 mg kg-1; treatment R) or their combination (treatment PR) were administered intravenously with a minimum of 1 week between treatments. Alertness, behavioral responsiveness (visual and tactile) and physiologic variables were measured before and up to 960 minutes after drug administration. Blood was collected for blood gas and acid-base analyses and measurement of plasma drug concentrations. Data were analyzed using repeated-measures analysis of variance or Friedman with Holm-Sidak and Wilcoxon rank-sum tests (p < 0.05). RESULTS: Systemic clearance significantly decreased and the area under the concentration-time curve significantly increased for both drugs in PR compared with P and R. Both PR and R decreased behavioral responsiveness and resulted in sedation for up to 240 and 480 minutes, respectively. Sedation was deeper in PR for the first 16 minutes. Heart rate significantly decreased in all treatments for at least 60 minutes, and PR significantly increased the incidence of severe bradycardia (<20 beats minute-1). CONCLUSIONS AND CLINICAL RELEVANCE: Although not associated with reduced behavioral responsiveness or sedation alone, propranolol augmented romifidine sedation, probably through alterations in romifidine pharmacokinetics, in horses administered PR. The occurrence of severe bradycardia warrants caution in the co-administration of these drugs at the doses studied.

Atlanto-axial approach for cervical myelography in a Thoroughbred horse with complete fusion of the atlanto-occipital bones.

A 2-year-old Thoroughbred gelding with clinical signs localized to the first 6 spinal cord segments (C1 to C6) had complete fusion of the atlanto-occipital bones which precluded performing a routine myelogram. An ultrasound-assisted myelogram at the intervertebral space between the atlas and axis was successfully done and identified a marked extradural compressive myelopathy at the level of the atlas and axis, and axis and third cervical vertebrae.

Approche atlanto-axiale pour une myélographie cervicale chez un cheval Thoroughbred avec la fusion complète des os occipito-atloïdiens. Un hongre Thoroughbred âgé de 2 ans avec des signes cliniques localisés aux 6 premiers segments de la colonne vertébrale (C1 à C6) avait une fusion complète des os occipito-atloïdiens qui empêchait la réalisation d'un myélogramme de routine. Un myélogramme par échographie à l'espace intervertébral entre l'atlas et l'axis a été réalisé avec succès et a identifié une myélopathie extradurale compressive prononcée au niveau de l'atlas et de l'axis ainsi que de l'axis et de la troisième vertèbre cervicale.(Traduit par Isabelle Vallières).

Risk of false positive genetic associations in complex traits with underlying population structure: a case study.

Genome-wide association (GWA) studies are widely used to investigate the genetic etiology of diseases in domestic animals. In the horse, GWA studies using 40-50,000 single nucleotide polymorphisms (SNPs) in sample sizes of 30-40 individuals, consisting of only 6-14 affected horses, have led to the discovery of genetic mutations for simple monogenic traits. Equine neuroaxonal dystrophy is a common inherited neurological disorder characterized by symmetric ataxia. A case-control GWA study was performed using genotypes from 42,819 SNP marker loci distributed across the genome in 99 clinically phenotyped Quarter horses (37 affected, 62 unaffected). A significant GWA was not achieved although a suggestive association was uncovered when only the most stringently phenotyped NAD-affected horses (n = 10) were included (chromosome 8:62130605 and 62134644 [log(1/P) = 5.56]). Candidate genes (PIK3C3, RIT2, and SYT4) within the associated region were excluded through sequencing, association testing of uncovered variants and quantitative RT-PCR. It was concluded that variants in PIK3C3, RIT2, and SYT4 are not responsible for equine neuroaxonal dystrophy. This study demonstrates the risk of false positive associations when performing GWA studies on complex traits and underlying population structure when using 40-50,000 SNP markers and small sample size.

Idiopathic headshaking: is it still idiopathic?

The clinical syndrome of equine idiopathic headshaking (HSK) was first described in the veterinary literature over 100 years ago, and the disorder continues to be a cause of substantial distress for the horse, frustration for the owner and therapeutic challenge for the veterinarian. This review presents a summary of the current knowledge of clinical signs, signalment, aetiopathogenesis, anatomy, diagnosis and treatment of idiopathic HSK. Recent advances in understanding the pathogenesis of the disease will be discussed with reference to human trigeminal neuralgia, along with the implications this may have for potential therapies.