Degenerative Axonopathy in a Tyrolean Grey Calf

Abstract

A 2.5-month-old female Tyrolean Grey calf weighing 99 kg from a cow-calf herd in eastern Switzerland was referred to the Clinic for Ruminants at the Vetsuisse Faculty, University of Berne with a history of pelvic limb weakness. A complete clinical examination indicated that the calf was normally developed for its age and breed. It was alert and responsive, but had a nervous demeanor. Examination of the cardiovascular and respiratory systems disclosed no abnormalities, except for a high heart rate in the first days of the calf's stay at the clinic (136-160 bpm; normal, 60-100 bpm). Heart rate returned to normal within a few days, and tachycardia was attributed to stress upon arrival in a new environment. Respiratory rate and body temperature were normal. Appetite was present, and food prehension, mastication, and swallowing were normal. Examination of the digestive system was within normal limits, as was that of the urinary tract. The musculoskeletal system was normally developed except for slight muscular atrophy of the thighs. Palpable articulations were neither enlarged nor painful. Foot trim was adequate, and the claws had no abnormalities.Upon neurological examination, the calf's behavior was normal except for its markedly nervous reactions to manipulations. The calf often stood with a wide-based stance in the thoracic and pelvic limbs (Fig 1, Video S1). It showed mild ambulatory paraparesis with moderateto-severe ataxia of the pelvic limbs and a tendency to fall to both sides (Fig 2, Video S2). Postural reactions were normal in the thoracic limbs and decreased to absent in the pelvic limbs. Segmental spinal reflexes of the thoracic limbs were normal, but decreased in both pelvic limbs. The menace response was absent bilaterally, pupillary light reflexes and vision were normal. Other cranial nerves were normal. The cutaneus trunci response was absent. Tail tone was decreased, but anal tone, defecation, and urination were normal. Palpation of the spine was not painful.The main lesion was localized in the spinal cord from T3 to S3. At this point, differential diagnoses included degenerative, infectious, and inflammatory lesions, as well as a malformation of the spinal cord.A CBC a and a blood chemistry profile b were performed. No abnormalities were detected in the CBC, and the chemistry profile disclosed a slight increase in aspartate aminotransferase activity ( 1 A differential cell count was not performed. No changes in the animal's neurological status were observed during its stay at the clinic. On day 16 of hospitalization, general anesthesia was induced with xylazine, butorphanol, and ketamine, and maintained by inhalation of isoflurane vaporized in oxygen. Electromyography (EMG) c was performed on the right side of the body, including thoracic and pelvic limb muscles, as well as paraspinal and tail muscles. No spontaneous activity was detected. The calf was euthanized at the end of the EMG procedure with an overdose of pentobarbital. All procedures complied with the Swiss legislation on animal welfare...

An Unusual Splice Defect in the Mitofusin 2 Gene (MFN2) Is Associated with Degenerative Axonopathy in Tyrolean Grey Cattle

“…We obtained one affected calf for clinical and neuropathological examination, which is described in more detail elsewhere [9]. Spinal ataxia was the most prominent feature (Figure 1).…”