AUSTRALIAN Stringhalt is often a seasonal condition that occurs in one or more horses grazing unimproved pastures after a break in the season.
It is believed that the condition is caused by a neurotoxin associated with the yellow flowering plant false dandelion or flatweed (Hypochoeris radicata).
When ingested in sufficient quantities the toxin affects the long myelinated nerves of the hindlimb resulting in the characteristic gait abnormality.
Stringhalt affected horses develop an unusual gait, with exaggerated flexion and jerky movement of the hindlimbs.
It is sometimes described as a ‘bunnyhopping’ action and it prevents the affected animals from being ridden or worked.
Clinical signs may be exaggerated by backing the horse or turning it in a tight circle.
Recovery from stringhalt is highly variable, dependent on the severity of clinical signs.
Mildly affected horses may recover within 2-3 months, more severe cases can take up to 18 months and some may never fully recover.
There are very few effective treatment options for stringhalt.
Affected horses should be removed from the weedy pasture, fed good quality feed and kept calm as agitation can lead to an increase in the severity of clinical signs.
There are some reports that supplements containing thiamine, magnesium, vitamin E and selenium are beneficial, however, there is little high quality evidence to support this.
There is a surgical procedure available to treat horses with stringhalt, in which the lateral digital extensor tendon is transected and a portion removed with the aim to help alleviate the clinical signs of the condition.
The results of surgery are highly variable with some horses showing immediate improvement while others show no improvement at all.
As always, prevention is better than cure and so it is important to ensure that your horses are grazing a weed free pasture.
Dr. Rebecca Hembrow BSc, BVMS, Ovens and Kiewa Veterinary Hospital