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Australian Stringhalt in Horses
WRITTEN BY: RIRDC Equine Research News   [Feb 1995]

Stringhalt Symptoms
Horse showing signs of Stringhalt

Stringhalt is a disease that results in an exaggerated flexion of one or both hind legs. Some horses may show only mild signs with slight flexion seen when the horse is backed or stopped suddenly. In other cases the flexion can be so severe that the front of the fetlock may hit the belly. If both back legs are affected a bunny hopping type of gait may develop. There can often be wasting of muscles around the gaskin. The condition affects the long nerves of the back which can also result in the larynx being partially paralysed. In these cases the horse cannot vocalise properly resulting in 'roaring'.

While there is not a lot known about the condition, some good research has been performed in Australia associated with the University of Melbourne Veterinary School (RF Slocombe, PJ Huntington, SCE Friend, LB Jeffcott, AR Luff and DL Finkelstein Pathological aspects of Australian Stringhalt Equine Veterinary Journal Vol. 24, No. 3, 1992 pg. 174; PJ Huntington, S Seneque, RF Slocombe, LB Jeffcott and AR Luff Use of phentoin to treat horses with Australian Stringhalt Australian Veterinary Journal Vol. 68, No. 7, 1991 pg. 221; PJ Huntington, LB Jeffcott, SCE Friend, AR Luff, DI Finkelstein and RJ Flynn Australian Stringhalt - epidemiological, clinical and neurological investigations Equine Veterinary Journal Vol. 21, No. 4, 1989 pg. 266). Some key points about the disease are as follows;

Usually a number of cases are seen in the one herd, although single cases have been reported. The condition may be due to an ingested toxin which affects some of the long nerves in the body. The pasture weed Catsear (Hypochoeris radicata) has been associated with many outbreaks of stringhalt. However, this association has not been confirmed in laboratory tests. Other plants such as Dandelion (Taraxacum officinale) have also been implicated.

Cases appear from late summer with a peak in February and are often associated with drier than normal summers. All breeds may be affected by Australian Stringhalt, although thoroughbreds seem to be more susceptible and ponies less susceptible.

Horses will usually recover if moved to a paddock where they are not grazing Catsear or Dandelion. Recovery can take a few days or up to 18 months. The average recovery period is 6-12 months. The anticonvulsant drug Dilantin® does ease the signs of the disease and can help to hasten recovery. Some severe cases that have not responded to being removed from pasture can have a surgical treatment. The surgery involves removing the lateral digital extensor tendon in the hind leg. This treatment has variable results but in some cases has proven to be very worthwhile

Assuming that Catsear is a major factor in the occurrence of Australian stringhalt, pasture management is the best option for minimising the chance of exposure to the problem.

Reprinted from the RIRDC Equine Research News with the permission of the Rural Industries Research and Development Corporation.

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