THE CLINICAL-DIFFERENTIATION OF NERVOUS AND MUSCULAR LOCOMOTOR DISORDERS OF SHEEP IN AUSTRALIA

Many of the nervous and muscular locomotor disorders that affect sheep throughout Australia are commonly referred to as 'staggers' syndromes . The range of clinical signs displayed by sheep suffering these disor ders is sufficiently diverse to enable each syndrome to be graded into one of 5 progressive clinical groups. The first group, the limb pares is syndromes, includes the primary myopathies associated with the inge stion of Ixiolaena brevicompta, Malva parviflora, and Trachymene ochra cea, as well as selenium and vitamin E disorders, Paroo virus staggers , congenital progressive muscular dystrophy, humpy back, hypocalcaemic muscle weakness, Tribulus terrestris staggers and tetanus. The second group is characterised by limb paresis with knuckling of the fetlocks , and includes the plant-associated toxicities of Romulea rosea, Stach ys arvensis, Trachyandra divaricata, and Tribulus micrococcus, togethe r with haloxon toxicity, enzootic ataxia (copper deficiency), and the probably genetic disorders of segmental axonopathy, neuroaxonal dystro phy, and degenerative thoracic myelopathy. Other locomotor disorders t hat fit more loosely into this group are listerial myelitis (post-dipp ing staggers), vitamin A deficiency, cervico-thoracic vertebral sublux ation, Stypandra glauca toxicity, Ipomoea spp toxicity, ivermectin tox icity, and botulism. The third group, the falling syndromes, includes the probably genetic disorders of thalamic cerebellar neuropathy, cere bellar abiotrophy, and globoid cell leucodystrophy, together with Swai nsona spp toxicity. The fourth group, the falling-with-tremors syndrom es, includes the plant-associated toxicities of phalaris staggers, per ennial rye grass staggers and nervous ergotism (Claviceps paspali). Th e fifth group, the convulsive syndromes, includes the polioencephaloma lacic entity nardoo fern (Marsilea drummondii) staggers, outbreaks of focal symmetrical encephalomalacia and the tunicaminyluracil toxicitie s known as annual ryegrass (Lolium rigidum) toxicity, annual beard gra ss (Polypogon monspeliensis) toxicity, blow away grass (Agrostis avena ceae) toxicity, and water damaged wheat (Triticum aestivum) toxicity. A dichotomous system is presented for the differential diagnosis of th ese groups of conditions.