A suspected inherited neuromuscular disease in dorset down sheep

Extract

Madam:– This is the first report in New Zealand of what appears to be an inherited neuromuscular disease in Dorset Down sheep. During two successive breeding seasons approximately 20% of ewes in a stud flock comprising 54 ewes and one ram gave birth to lambs showing pronounced weakness of either both hind or all four limbs. Over 20 male or female single, twin, or one of a pair of twin lambs were affected. From birth these animals were alert and could raise their heads but they were unable to stand. Characteristically they lay with hindlimbs tucked under their bodies and forelimbs splayed sideways. Most affected lambs were slaughtered but those which were hand reared made a partial recovery. One such animal examined at five weeks of age showed pronounced flexion of the tarsal joints so that it walked on its hocks. The forelimbs were held unusually straight and the carpal joints occasionally knuckled over when the lamb walked. The limb joints were fully mobile upon manipulation and the hindlimbs were able to bear weight for short periods of time.     

Electrophysiology in neuromuscular disease.

Electrophysiologic assessment of the peripheral nervous system is an integral part of the diagnostic workup for neuromuscular disease. This article is designed to provide insight into the importance and limitations of the various testing procedures now available in veterinary electrophysiology and to provide the reader with an understanding of the theory behind each of these procedures. The article also provides a guideline for the interpretation and clinical significance of each of the available tests.     

The clinical examination for neuromuscular disease.

Neuromuscular disease can present even the most astute clinician with a challenging diagnostic dilemma. This article focuses on the neuroanatomy and the historical, physical, and neurologic examination findings observed in many of the neuromuscular disorders affecting dogs and cats. In addition, some common laboratory tests and imaging modalities used in the diagnosis of neuromuscular disease, including routine radiography, computed tomography, and magnetic resonance imaging, are discussed. A brief discussion of sensory nerve disorders is also presented.     

Congenital and inherited renal disease of small animals.

Congenital renal diseases are present at birth and may be determined genetically; familial renal disorders occur in related animals with a higher frequency than would be expected by chance, and frequently are inherited. The most common familial disorders in cats and dogs include renal amyloidosis, renal dysplasia, polycystic kidneys, basement membrane disorders, and tubular dysfunction (Fanconi's syndrome). This article alerts the veterinarian to commonly observed congenital and hereditary conditions of the kidneys in small animals.     

A familial degenerative neuromuscular disease of Gelbvieh cattle.

A degenerative skeletal muscle disease with vascular, neurologic, and renal lesions and a probable familial distribution was identified in 4-20-month-old purebred Gelbvieh cattle. Thirteen affected animals were confirmed from 6 separate beef herds, with a mortality rate of 100%. Clinical signs in affected animals consisted of ataxia, weakness, and terminal recumbency. Gross and histologic muscle lesions were indicative of nutritional myopathy of ruminants, with a lack of myocardial lesions in most cases and only rare myocardial changes in a few animals. Acute to chronic lesions in most large skeletal muscle groups consisted of degeneration, necrosis, regeneration, fibrosis, and atrophy. Fibrinoid necrosis of arterioles was a common feature in multiple tissues. Lesions in the spinal cord white matter and peripheral nerves consisted of degeneration of the dorsal columns and axons, respectively. Changes in the kidneys consisted of chronic interstitial nephritis with fibrosis, hyaline droplet change and tubular epithelial vacuolar change and were most severe in the older calves. Intracytoplasmic myoglobin and iron were demonstrated within the hyaline droplets in degenerate renal cortical tubular epithelial cells. Vitamin E levels were deficient in most (6/7) of the animals tested. Investigation of the pedigree of affected animals revealed a common ancestry for all but 1 of the animals whose parentage could be traced. This investigation suggests that a hereditary metabolic defect, possibly involving antioxidant metabolism, could be responsible for this condition. Renal disease, possibly secondary to myoglobinuria, may be unique to this bovine condition.     

Organelle pathology in metabolic neuromuscular disease: an overview.

The spectrum of metabolic neuromuscular disorders is wide. Most inherited metabolic diseases are related to enzyme defects within lysosomes but recent advances emphasize abnormalities of mitochondria, peroxisomes and intermediate filaments. In this overview, organelle pathology is described in the context of both the clinical manifestations and the biochemical and/or molecular aspects of the disease. Among the many clinical presentations of mitochondrial disorders three emerge as distinctive entities: mitochondrial encephalopathy with lactic acidosis and stroke-like symptoms, mitochondrial encephalopathy with ragged-red fibers, and Kearns-Sayre syndrome. Peroxisomal disorders are associated with numerous biochemical defects, the most frequent of which are Zellweger's syndrome, neonatal adrenoleukodystrophy, and infantile Refsum's disease. Disorders of cytoskeletal proteins are associated with distinctive pathological accumulation of intermediate filaments but are without confirmed evidence of a biochemical defect. Understanding the role that organelle pathology plays in the pathogenesis of cellular disturbance or demise is essential to the elucidation of the pathogenesis of metabolic disorders.     

An inherited enchondrodystrophy in the English Pointer dog. A new disease

This report describes the clinical, radiological, pathological and genetic features of an inherited dwarfism in the English Pointer. Gross enlargement of the distal ulnar, radial and tibial growth plates occurred in the first 6 weeks of life and radiographic skeletal abnormalities were present at other sites. The enlargement was due to increase in width of the zone of hypertrophic cartilage, but the columns of chondrocytes were well ordered. By 12 weeks of age an unusual type of degeneration was present beneath the surface of articular cartilage; this developed to widespread, patchy erosion of joint surfaces by 32 weeks. The genetics are compatible with a homozygous recessive mode of inheritance.     

Canine trichinosis with signs of neuromuscular disease

A six-year-old fox terrier bitch, used for badger hunting, developed acutely progressive painless disturbance of locomotion with pronounced weakness. Evidence of central nervous disease or myasthenia gravis was not present. Muscle histology revealed trichinella larvae and changes consistent with a combined inflammatory myopathy and neuropathy. An enzyme-linked immunosorbent assay (ELISA) showed significantly increased serum levels of antibodies to Trichinella spiralis antigen. It is likely that the signs of neuromuscular disease shown by the dog were due to the trichinella infection. The case illustrates that symptomatic trichinosis should be considered in the clinical workup of myopathies in dogs with access to potentially trichinella-infected wildlife.     

Variability in limb malformations and possible significance in the pathogenesis of an inherited congenital neuromuscular disease of Charolais cattle (syndrome of arthrogryposis and palatoschisis)

Limb abnormalities in 30 calves with an inherited congenital neuromuscular disorder known as syndrome of arthrogryposis and palatoschisis were classified according to the range of severity of joint deformity in either flexion or extension, and restricted joint movement. Joint movement was variably affected; it was either normal, lax, restricted in the range of mobility, or occasionally, fixed. The characteristic findings were: bilateral hyperextension of the hind fetlock, flexion deformity of the forelimb that particularly involved the fetlock and the carpus, with restricted articular movement and complete rigidity in some cases. One-third of calves also had medial deviation of the forelimb due to angular deformity of articular surfaces in the carpus. All nine live calves were floppy due to marked generalized muscular hypotonia. Birth weight of deformed calves was reduced. In some calves muscle development was impaired as judged by muscle weight, and histological examination. In some calves the gross appearance, muscle weight and histological examination revealed no abnormal development and indicated that the effects on skeletal muscle were secondary. No lesions were found in the spinal cord of 23 of 24 calves examined histologically. The remaining calf had a localized cavitation in the dorsal white matter at T2-3. Based on the observations in calves in this study it is proposed that both primary and secondary factors contribute to the phenotypic expression of this congenital deformity. The primary lesion is considered to be a neurogenic abnormality of differentiation in the central nervous system. Cytogenetic analysis of 16 carrier cows and two deformed calves showed normal karyotypes. Serology for Akabane virus in 16 carrier cows was negative.     

Cytologic diagnosis of disease in amphibians.

Cytology is an inexpensive yet powerful diagnostic tool that allows for rapid diagnosis of many common disease conditions in amphibian patients. Although the emphasis of this article is on infectious diseases, there is great potential for application of cytologic diagnosis to variety of medical conditions as the knowledge base in amphibian medicine and pathology continues to grow. Routine methods used that may fall under the umbrella of cytology range from wet mount examination of skin scrapings (or gill biopsies of larvae) to examination of stained impression smears. Routine Romanowsky's-type stains work well for amphibian samples. Preparation of multiple smears is always recommended to allow for use of special staining procedures.     

Characteristics, diagnosis, and treatment of inherited platelet disorders in mammals

Inherited intrinsic platelet disorders have been identified in dogs, cattle, horses, and cats as well as other animals. The prevalence of mutations in some breeds is high, making these disorders potentially as common as von Willebrand disease in certain breed lineages.