Prevalence of genetic mutations in horses with muscle disease from a neuromuscular disease laboratory

Allele frequency of muscular genetic disorders in bull-catching (vaquejada) quarter horses

Quarter horses (QH), a prominent athletic breed in Brazil, are affected by muscular genetic disorders such as myosin-heavy chain myopathy (MYHM), polysaccharide storage myopathy (PSSM1), hyperkalemic periodic paralysis (HyPP), and malignant hyperthermia (MH). Bull-catching (vaquejada), primarily involving QH, is a significant equestrian sport in Brazil. Since the allele frequencies (AF) of MYHM, PSSM1, HyPP, and MH in vaquejada QH remain unknown, this study evaluated the AF in 129 QH vaquejada athletes, specifically from the Brazilian Northeast. These variants were exclusively observed in heterozygosity. The MYHM exhibited the highest AF (0.04 ±0.01), followed by PSSM1 (0.01 ±0.01) and the HyPP variant (0.004 ±0.01), while the MH variant was not identified in this study. This study represents the first identification of these variants in vaquejada QH, emphasizing the need to implement measures to prevent the transmission of pathogenic alleles and reduce the occurrence of clinical cases of these genetic diseases.

Predicted genetic burden and frequency of phenotype-associated variants in the horse

Disease-causing variants have been identified for less than 20% of suspected equine genetic diseases. Whole genome sequencing (WGS) allows rapid identification of rare disease causal variants. However, interpreting the clinical variant consequence is confounded by the number of predicted deleterious variants that healthy individuals carry (predicted genetic burden). Estimation of the predicted genetic burden and baseline frequencies of known deleterious or phenotype associated variants within and across the major horse breeds have not been performed. We used WGS of 605 horses across 48 breeds to identify 32,818,945 variants, demonstrate a high predicted genetic burden (median 730 variants/horse, interquartile range: 613-829), show breed differences in predicted genetic burden across 12 target breeds, and estimate the high frequencies of some previously reported disease variants. This large-scale variant catalog for a major and highly athletic domestic animal species will enhance its ability to serve as a model for human phenotypes and improves our ability to discover the bases for important equine phenotypes.

Congenital heart defects in Arabian horses and the prospects of genetic testing: A review

Congenital heart defects (CHDs) can have profound and potentially life-threatening consequences on horses' health and performance capability. While CHDs are rare in the general horse population, the Arabian breed is disproportionately overrepresented and thus is widely suspected to be genetically predisposed. This review discusses the most common CHDs in Arabian horses, including ventricular septal defect (VSD), tetralogy of Fallot (TOF), patent duct arteriosus (PDA), tricuspid valve atresia (TVA) and atrial septal defect (ASD). This review also explores how future research into the genetic factors that likely underpin many CHDs can revolutionise the way these disorders are managed in Arabian horses.

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.

Anatomical variations of the flexor carpi ulnaris in the fetal period

Introduction: The Flexor Carpi Ulnaris (FCU) is a part of the palmar the forearm muscle group and one of the most important muscles for upper limb functioning - is responsible for flexion and adduc­tion of the hand at the radio-carpal joint. There are clinically significant but rare anatomical variations of FCU. The variability of the FCU has not been described up to now, and no typology of the muscle based on its more variable terminal attachment has been created. Aim of the study: Determination of FCU muscle typology based on available fetal material. Material and methods: A total of 114 human fetuses (53 female, 61 male) between 117 and 197 days of fetal life were eligible for the study. Preparations were carried out using classical anatomical techniques based on a previously published procedure. Thanks to that significant anthropometric landmarks were vis­ible for the gathering of metric measurements. Metric measurements were taken and statistically analysed using R-Project software. Results: A new typology was created based on variable muscle insertions. Additionally, the presence of an atypically located, additional, separated muscle belly was described. A comparison of measurements of the left upper limb in relation to the right upper limb showed significant differences for forearm length to the anthropometric point of the stylion radiale, limb length, total FCU length and FCU length which means that the left limb is longer than the right limb. A comparison of FCU insertion types between left and right upper limb showed there’s no significant difference between counts of each type. Conclusion: The FCU is a muscle that is easy to palpate and may therefore act as a topographical marker for healthcare professionals. Knowledge of its variability is not only of theoretical importance but also has clinical sig­nificance. The current publication demonstrates presence of variability in FCU terminal attachment. Certainly, this topic requires further research and continued work on a detailed understanding of forearm anatomy in the fetal period.