H. W. Leipold

Review of spinal muscular atrophy (SMA) in brown Swiss cattle.

Spinal muscular atrophy (SMA) is a heritable condition in Brown Swiss cattle characterized by profound muscular atrophy affecting appendicular muscles, particularly of the rear limb. Axial muscles are also affected. The affected ventral horn neurons are initially swollen and chromatolytic; this is followed by a shrunken appearance, necrosis, and neuronophagia. It is not uncommon to see “empty beds” that are ghosts of previous perikarya. There is an obvious gliosis with the presence of glial nodules. A total of 53 SMA cases were either reported to us or received and studied by the Congenital Defects Laboratory at Kansas State University. All calves underwent a thorough clinical examination. They were then euthanatized using T-61 a and immediately underwent a standardized necropsy procedure. Brains were obtained by removal of the dorsal cranium, and spinal cords were removed by removal of the dorsal vertebral arches. Muscle samples were taken and attached by stapling to tongue depressors for identification. Peripheral nerves were sampled also. Tissues were processed for light and electron microscopy studies. Iowa was the geographic origin of 10 of the cases, followed by Wisconsin and Texas with 5 cases each.

Congenital Anemia, Dyskeratosis, and Progressive Alopecia in Polled Hereford Calves:

A new syndrome of anemia, alopecia, and dyskeratosis was identified in Polled Hereford calves in this study. Cutaneous changes included hyperkeratosis and hair loss around the muzzle and ear margins, which progressed to a generalized alopecia and hyperkeratotic dermatitis. Histologically, orthokeratotic hyperkeratosis with dyskeratosis of epidermal and follicular keratinocytes was present. Alopecia was correlated with dyskeratosis of Huxleys layer and an increasing proportion of follicles in the telogen phase of the hair cycle. Dermatitis was characterized by a mild dermal mononuclear cell infiltrate and mild lymphocytic perivascular dermatitis. The anemia present at birth was nonprogressive and was classified as normochromic and normocytic to macrocytic. Reticulocytosis was absent, but bone marrow was markedly hyperplastic. Nuclear cytoplasmic asynchrony of the rubricyte and metarubricyte stages occurred in the bone marrow. Abnormal rubricyte nuclei and maturation arrest at the late rubricyte stage were common. Cytologic features of the erythroid series are similar to those of type I congenital dyserythropoietic anemia of human beings. Genealogic features suggest that this is a primary hereditary defect. The mode of inheritance, however, remains to be determined.

Hereditary Syndactyly in Angus Cattle

Twenty-five syndactylous Angus cattle, characterized pathologically, were reported from 16 herds in 10 states from 1979 to 1994. Twenty-one (84%) had all 4 legs syndactylous, 3 (12%) had 3 legs syndactylous, and 1 (4%) had 2 legs syndactylous. All syndactylous cattle walked with considerable difficulty. Hooves of aged animals became curled and bent laterally or medially. Affected hooves had the appearance of a truncated cone, the base of which was located at the coronary band. Most hooves were fused completely with no indication of dual anlage. An occasional hoof had a distal notch, and other hooves had a dorsally located groove indicating dual embryonic origin. Lateral dewclaws were enlarged in most cases. Radiographs and dissections of limbs of 19 animals revealed a consistent pattern of fusion in most affected calves. Lesions included 1 or more of the following: disappearance of the large metacarpal and metatarsal intertrochlear notches, horizontal fusion of 1 or more carpals and tarsals, fusion of proximal sesamoids, 1 distal sesamoid, and fusion of paired phalanges. Evidence of a genetic cause consisted of 11 syndactylous calves among 70 offspring of 4 3/4 sib families, 8 preterm syndactylous fetuses among 148 preterm fetuses and 13 calves in progenies of 19 animals tested for possible heterozygosity, and 5 syndactylous calves from matings of an Angus syndactylous bull with 1 Angus and 4 Holstein syndactylous cows. Data were consistent with recessive inheritance at a single locus. Angus cattle with sydactytly had a larger number of affected limbs than did syndactylous Holsteins and their Angus crosses, suggesting existence of 2 recessive alleles. The allele of Holsteins (sy H) appeared to influence phenotypic expression in a dominant pattern over the Angus allele (sy A). Both sy A and sy H alleles acted as reccessives to the normal SY allele. Phenotypic effects on limb development were most dramatic in calves with the sy A/sy A genotype.

Congenital Syndrome of Anophthalmia-Microphthalmia with Associated Defects in Cattle

An anophthalmia-microphthalmia syndrome occurred in 26 animals from several dairy and beef cattle breeds. Fifteen were bilaterally anophthalmic, 6 unilaterally anophthalmic, 3 microphthalmic in 1 eye and anophthalmic in the other, 1 bilaterally microphthalmic, and 1 unilaterally microphthalmic. Ten calves had other abnormalities involving the caudal portions of the spinal column including taillessness. Five calves were dissected and the contents of the orbital cavity and optic nerve examined macroscopically and microscopically. The sphenoid bone was malformed and the optic nerve vesicle-like. The remnants of ocular structures were histologically variable. The etiology of these defects in cattle is unknown.

Leukoplakia of the Esophagus and Stomach of a Foal

A 4-month-old male quarter horse weighing 114 kg was presented for necropsy. It had had surgery for a type 4 and 5 metatarsal deviation. There was medial deviation of the left hind limb distal to the fetlock, with lateral deviation from the tarsus to the fetlock. The animal lived 92 days after surgery. During the entire period there was infection with chronic drainage in the area of surgery. The foal received intensive antibiotic and phenylbutazone therapy, receiving phenylbutazone for over one-third of the 92 days. During its last few days of life, the