Longitudinal study of Australian stringhalt cases in France.

Seventy horses with clinical evidence of Australian stringhalt were studied in France from 2003 to 2008. All horses but one had history of bilateral stringhalt and grazed pastures infested with Hypochoeris radicata (L.). They displayed hind limbs hyperflexion and an abnormal gait because of a distal axonopathy with a skeletal muscle denervation and atrophy. Fifty percentage of them recovered spontaneously in 8 months, and only the more affected horses were unable to recover even if they looked healthy on dry and hot days. Clinical troubles revealed also depression or aggressive behaviour, suggesting that central nervous system might be affected. Treatment with phenytoin resulted in a rapid noticeable improvement of stringhalt in some horses but the administration of taurine seems to improve behavioural disorders. Deeply affected horses (grade III and more of Huntington's classification at the beginning) must be treated with phenytoin when the weather is muddy and damp because they still display stringhalt when they are afraid or at the beginning of the work.