Clinicopathological and pedigree investigation of a novel spinocerebellar neurological disease in juvenile Quarter Horses in North America.

BACKGROUND: In 2020, a novel neurologic disease was observed in juvenile Quarter Horses (QHs) in North America. It was unknown if this was an aberrant manifestation of another previously described neurological disorder in foals, such as equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM). HYPOTHESIS/OBJECTIVES: To describe the clinical findings, outcomes, and postmortem changes with Equine Juvenile Spinocerebellar Ataxia (EJSCA), differentiate the disease from other similar neurological disorders, and determine a mode of inheritance. ANIMALS: Twelve neurologically affected QH foals and the dams. METHODS: Genomic DNA was isolated and pedigrees were manually constructed. RESULTS: All foals (n = 12/12) had a history of acute onset of neurological deficits with no history of trauma. Neurological deficits were characterized by asymmetrical spinal ataxia, with pelvic limbs more severely affected than thoracic limbs. Clinicopathological abnormalities included high serum activity of gamma-glutamyl transferase and hyperglycemia. All foals became recumbent (median, 3 days: [0-18 days]), which necessitated humane euthanasia (n = 11/12, 92%; the remaining case was found dead). Histological evaluation at postmortem revealed dilated myelin sheaths and digestion chambers within the spinal cord, most prominently in the dorsal spinocerebellar tracts. Pedigree analysis revealed a likely autosomal recessive mode of inheritance. CONCLUSIONS AND CLINICAL IMPORTANCE: EJSCA is a uniformly fatal, rapidly progressive, likely autosomal recessive neurological disease of QHs <1 month of age in North America that is etiologically distinct from other clinically similar neurological disorders. Once the causative variant for EJSCA is validated, carriers can be identified through genetic testing to inform breeding decisions.

Subtourniquet pressures generated by application of wide-rubber tourniquets in standing, sedated horses.

OBJECTIVE: To determine the influence of location and movement on subtourniquet pressure (STP) generated by application of a wide-rubber tourniquet (WRT) on equine limbs. STUDY DESIGN: Randomized experimental cross-over design. ANIMALS: Six standing, sedated horses. METHODS: Horses were sedated with detomidine hydrochloride (0.2 µg/kg IV), and 4 investigators applied WRTs to the antebrachium (AB), gaskin (GK), and midmetacarpus (MC) of each horse in a predetermined, randomized order. Subtourniquet pressure was consequently measured at 10-minute intervals (T0, T10, T20, T30) for 30 minutes. Indirect systolic blood pressure (SBP) was measured presedation, postsedation, and throughout the tourniquet application period. Target STP was established as SBP + 100 mm Hg. Limb movements at each location were classified as none, low, moderate, or high, on the basis of counts and magnitude. RESULTS: Mean STP did not change with time (P = .93) and exceeded SBP by 163 mm Hg (95% CI 122-205), 185 mm Hg (95% CI 156-214), and 402 mm Hg (95% CI 351-454) at the AB, GK, and MC, respectively. Mean STP at each location exceeded the target STP in 59 of 70 (81%) of the trials. Limb movements affected STP generated by tourniquets at the AB (P = .04) and MC (P < .0001) but not at the GK (P = .67). CONCLUSION: Wide-rubber tourniquets applied at the AB, GK, and MC generated STP >100 mm Hg above SBP for 30 minutes in standing, sedated horses. CLINICAL SIGNIFICANCE: Wide-rubber tourniquets as applied in this study can achieve and maintain the current recommended STP (SBP + 100 mm Hg) for equine IV regional limb perfusion. Number and magnitude of limb movement can decrease STP over time, potentially reducing the efficacy of a WRT.

Effect of a monovalent vaccine against Leptospira borgpetersenii serovar Hardjo strain hardjobovis on fertility in Holstein dairy cattle.

OBJECTIVE: To determine whether vaccination with a monovalent vaccine against Leptospira borgpetersenii serovar Hardjo strain hardjobovis would improve reproductive efficiency in Holstein cattle in a commercial dairy setting. DESIGN: Randomized controlled trial. ANIMALS: 1,894 Holstein cows and heifers from a Central California dairy. PROCEDURES: Cattle were assigned to undergo SC administration of a monovalent vaccine against Leptospira borgpetersenii serovar Hardjo strain hardjobovis (n = 986) or a placebo (lactated Ringer's solution; 908). At the end of their lactation period, cows received 2 doses of the vaccine or placebo, 28 to 35 days apart, with the initial dose administered in conjunction with oxytetracycline. Heifers received the same treatments, with the second dose administered at least 2 weeks before their entrance into the heifer breeding pen. Urine and blood samples were collected from randomly selected cattle immediately before and 1 year after the trial began and submitted for fluorescent antibody and microscopic agglutination testing to identify any infecting Leptospira serovar. RESULTS: The initial herd prevalence of active infection with strain hardjobovis was 13% (6/46 tested cattle), followed by 15% (6/40) 1 year after the trial began. The odds of heifers conceiving over the period at risk for conception, regardless of vaccination, was approximately 2.8 times as high as for primiparous and pluriparous cows. Survival analysis of days from parturition to conception revealed that the vaccine protocol had no effect on the probability of conception between the vaccinated and control groups. The vaccine protocol had no impact on pregnancy loss. CONCLUSIONS AND CLINICAL RELEVANCE: The evaluated vaccination protocol against Leptospira strain hardjobovis was not effective in improving reproductive efficiency in commercial Holstein dairy cows or in decreasing urine shedding of leptospires.