A New Inherited Muscular Disorder in Japanese Quails (Coturnix coturnix japonica)

Thirteen adult mutant (LWC strain) Japanese quails ( Coturnix coturnix japonica), between the ages of 8 and 60 weeks were examined for a progressive muscular disorder. The disorder, inherited as an autosomal dominant trait, was clinically apparent as early as 28 days of age; it was characterized by generalized myotonia, muscle stiffness, and muscle weakness. Affected birds were identified by their inability to lift their wings vertically upward and by their inability to right themselves when placed on their dorsum. Electromyographic studies in two mutant quails showed high-frequency repetitive discharges comparable to those of myotonic runs. These discharges persisted after nerve resection. The distinctive histopathologic changes in the various muscles examined were ring fibers, sarcoplasmic masses, and internal migration of sarcolemmal nuclei. A slight decrease in the size of type IIB muscle fibers and a slight increase in the size of type IIA fibers were observed in the M. pectoralis thoracicus of affected quails. In older affected birds, inter- and intrafascicular fatty infiltration with replacement of type IIB fibers by fat cells was seen in the pectoral muscles. Single fiber necrosis, nonspecific lymphorrages, and variations in the muscle fiber size and shape were also noted. The typical muscle lesions and multisystem involvement, which was manifested by testicular degeneration and atrophy in the male LWC specimens and bilateral lenticular cataracts in 6 of 13 affected mutant quails, suggest resemblance of this new inherited muscular disorder to myotonic dystrophy in man.

A Congenital Progressive Ovine Muscular Dystrophy

A congenital progressive myopathy affecting 2% of a flock of Merino sheep involved most of the muscles of the pelvic and pectoral girdles. The vastus intermedius muscle was consistently affected; at 2 years of age 50% of its fibers were replaced by fat and at 5 years almost all. Lesions were bilaterally symmetrical. Usually all components of the quadriceps muscle were involved, but scattered affected fibers were found in most other appendicular muscles. The lesions in the quadriceps muscles resulted in inability to flex the femoro-tibial joint, with consequent difficulty in locomotion, which, under range conditions, resulted in death from inability to forage. Histologically, affected muscles had rounded fibers with central and peripheral sarcoplasmic masses. The fibers contained vesicular nuclei that usually formed rows of up to 15, but occasionally up to 50. In 6-week-old lambs, muscle fibers ranged in diameter from 15-100 μ. No lesion was detected in the peripheral or central nervous system.