Stringhalt in an ewe - a case report.

Stringhalt in an ewe - a case report Introduction Stringhalt has been described in horses frequently and is a disease that results in a disproportionated flexion of one or both hind limbs during locomotion or while rest. In cattle the disease is uncommon. The cause of stringhalt is unknown, although the condition has been attributed to numerous factors over the years. In horses, 2 different forms of stringhalt are described on the basis of their different epidemiological and outcome features. The gait is characterized by hyperflexion of one or both pelvic limbs during movement or while standing. In some cases only mild signs with slight flexion are noted when the horse is backed or stopped suddenly. In horses with advanced illness the flexion can be so severe that the front of the fetlock may hit the belly. A bunny hopping type of gait may be noted if both hind limbs are affected. Sometimes an atrophy of the muscles of the thigh is obvious. Conventional or classic stringhalt occurs sporadic and is defined due to its clinical manifestation without other distinguishing factors. The epidemic form of stringhalt, called Australian stringhalt, first described in 1848, is most commonly seen in horses in meadows at the end of summer or beginning of autumn when the summer has been hot and dry. The disease often affects several horses in the same pasture and occurs in epidemics; both hindlimbs are generally affected, sometimes the thoracic limbs may be involved, too. A toxic factor is postulated, furthermore divers plants have been investigated, but no clear cause is known. There exist only one report about real stringhalt in cattle and a few about similar apraxia, associated with spasms of the hind limbs. Material and methods An 8 year old female White Mountain Mutton sheep was presented with the history of a severe apraxia of both hind limbs of 6 months duration. The ewe was subjected to a lameness evaluation including palpation of the limbs and observation of the sheep at walk and trot. Flexion test of the digital joints was performed. After physical examination, radiography of the tarsal joints and the vertebral and lumbar spine was carried out. Diagnostic analgesia with procainhydrochloride consisting of the tibial and fibular (peronal) nerves was conducted on both hind limbs. Furthermore an intra-articular analgesia of the right talocrural joint was carried out. Results The sheep showed exaggerated flexion of the hock, involving in turn both hind limbs. Sometimes, the limbs were raised so much, that the fetlock joint nearly touched the ventral abomen. The stringhalt action could be noted while standing, the gait was normal. While standing the limbs were raised alternately with a frequency of 2 to 3 seconds. There was a decrease in the frequency of the flexion of the limbs when the sheep was diverted by feed intake or other activities. On the right hind limb a moderate lameness was noted while walking. Arthrosis of the tarsal joints, spondyloses of the vertebral column and calcinosis intervertebralis of the lumbar spine were diagnosed radiologically. Conclusion The true causes of stringhalt are unknown. Most scientists believe the cause of stringhalt is from certain neuromuscular conditions. In Australian stringhalt, a distal axonopathy leading to neurogenic muscle atrophy was found by histopathological research. Stringhalt in cattle has seldom been described. The ewe was suffering from spondylosis of the cervical vertebrae as well as calcinosis intervertebralis of the lumbar spine. The arthrosis of the tarsal joint was an additional diagnostic finding and caused propably by a trauma reported several years before.