Stringhalt is a sudden flexion of one or both hind legs in the horse, most easily seen while the horse is walking or trotting. It is most evident when the horse is backing up slowly, turning on the affected leg, or suddenly frightened. It can involve one or both hind legs of the horse. It is a spasmodic contraction of the lateral extensor tendons of the hind legs.
An example of bilateral stringhalt in a horse: the hocks are spasmodically and rapidly flexed with the feet held high before quick placement back on the ground. The condition is more evident during turning and backing.
Australian stringhalt was described and differentiated from classical stringhalt in 1884.[2] Australian stringhalt is differentiated from classical stringhalt by the severity, occurrence of outbreaks, distinct seasonal pattern and the ability of affected horses to recover spontaneously.[3] This condition is characterised by the sudden exaggerated flexion of either one or both hocks. This form of stringhalt most commonly occurs in the summer and autumn while horses are out on pasture. Epidemics of Australian stringhalt are usually witnessed during drought or abnormally dry conditions.
Affected areas in the horseedit
The long digital extensor muscle (usually in the hind limb) is the muscle that appears to be the most affected by this condition.[2] The most severe muscle lesions have been found within the long and lateral digital extensors and lateral deep digital flexor. The location of neuromuscular lesions in Australian stringhalt may be explained by the susceptibility of longer, larger myelinated nerve fibres to injury.[3] Regenerating nerve fibres with disproportionately thin myelin sheaths are more common in the proximal parts of affected nerves in horses with Australian stringhalt. Distal axonopathy occurs most severely in the longest nerve in the horse.[4] The cause for this distal axonopathy remains unknown.[3]
Treatmentedit
Horses affected with this condition rarely recover without surgical intervention, although there have been some instances where horses have recovered without treatment. The recovery time in affected horses can range from three months to three years.[2] Horses may be affected so severely that euthanasia is necessary. It is unknown how long it takes for clinical signs to develop after the exposure to the cause of the condition.[2]
The majority of horses affected by stringhalt are dependent upon pasture for nutrition.[2] Removal of the horse from its original paddock containing low-quality pasture, weeds and native grasses, along with dietary control, was the most common and successful treatment. Lateral digital extensor tenectomy has also been used as a treatment by veterinarians with a success rate of just over 50%.[2]
Phenytoin has been used in the management of Australian stringhalt.[5] Two weeks after treatment with phenytoin, significant improvement was observed in the gait abnormality of horses affected with Australian stringhalt at the trot and canter, but no significant improvement was observed at the walk or while turning.[5]
Causesedit
Hypochaeris radicata (flatweed) is linked to some cases of stringhalt in horses.
The most common plant species that have been found and identified in pastures where affected horses were located include: flatweed (Hypochaeris radicata), sheep's sorrel (Rumex acetosella) and couch grass (Elymus repens). The type of nerve damage sustained in horses with Australian stringhalt suggests a mould toxin (mycotoxin) or a fungal 'poison' found in the soils may be a cause for this condition. Mycotoxins can directly affect the long myelinated nerves in the hind limbs.[2]
^Cahill, JI; Goulden, BE; Jolly, RD (September 1986). "Stringhalt in horses: a distal axonopathy". Neuropathology and Applied Neurobiology. 12 (5): 459–75. doi:10.1111/j.1365-2990.1986.tb00054.x. PMID 3024050. S2CID 26816155.
^ abHuntington, PJ; Seneque, S; Slocombe, RF; Jeffcott, LB; McLean, A; Luff, AR (July 1991). "Use of phenytoin to treat horses with Australian stringhalt". Australian Veterinary Journal. 68 (7): 221–4. doi:10.1111/j.1751-0813.1991.tb03210.x. PMID 1929987.
January 01, 1970
stringhalt, sudden, flexion, both, hind, legs, horse, most, easily, seen, while, horse, walking, trotting, most, evident, when, horse, backing, slowly, turning, affected, suddenly, frightened, involve, both, hind, legs, horse, spasmodic, contraction, lateral, . Stringhalt is a sudden flexion of one or both hind legs in the horse most easily seen while the horse is walking or trotting It is most evident when the horse is backing up slowly turning on the affected leg or suddenly frightened It can involve one or both hind legs of the horse It is a spasmodic contraction of the lateral extensor tendons of the hind legs source source source source source An example of bilateral stringhalt in a horse the hocks are spasmodically and rapidly flexed with the feet held high before quick placement back on the ground The condition is more evident during turning and backing There are four forms of stringhalt 1 Australian stringhalt a flatweed Hypochaeris radicata is the suspected cause Pseudostringhalt the apparent result of a painful condition in the affected leg Unilateral stringhalt cause unknown but often relieved by section of the lateral extensor tendon Bilateral stringhalt in two out of two affected horses necropsied abnormal thalamus Treatment varies Contents 1 Australian stringhalt 1 1 Affected areas in the horse 1 2 Treatment 1 3 Causes 2 See also 3 ReferencesAustralian stringhalt editAustralian stringhalt was described and differentiated from classical stringhalt in 1884 2 Australian stringhalt is differentiated from classical stringhalt by the severity occurrence of outbreaks distinct seasonal pattern and the ability of affected horses to recover spontaneously 3 This condition is characterised by the sudden exaggerated flexion of either one or both hocks This form of stringhalt most commonly occurs in the summer and autumn while horses are out on pasture Epidemics of Australian stringhalt are usually witnessed during drought or abnormally dry conditions Affected areas in the horse edit The long digital extensor muscle usually in the hind limb is the muscle that appears to be the most affected by this condition 2 The most severe muscle lesions have been found within the long and lateral digital extensors and lateral deep digital flexor The location of neuromuscular lesions in Australian stringhalt may be explained by the susceptibility of longer larger myelinated nerve fibres to injury 3 Regenerating nerve fibres with disproportionately thin myelin sheaths are more common in the proximal parts of affected nerves in horses with Australian stringhalt Distal axonopathy occurs most severely in the longest nerve in the horse 4 The cause for this distal axonopathy remains unknown 3 Treatment edit Horses affected with this condition rarely recover without surgical intervention although there have been some instances where horses have recovered without treatment The recovery time in affected horses can range from three months to three years 2 Horses may be affected so severely that euthanasia is necessary It is unknown how long it takes for clinical signs to develop after the exposure to the cause of the condition 2 The majority of horses affected by stringhalt are dependent upon pasture for nutrition 2 Removal of the horse from its original paddock containing low quality pasture weeds and native grasses along with dietary control was the most common and successful treatment Lateral digital extensor tenectomy has also been used as a treatment by veterinarians with a success rate of just over 50 2 Phenytoin has been used in the management of Australian stringhalt 5 Two weeks after treatment with phenytoin significant improvement was observed in the gait abnormality of horses affected with Australian stringhalt at the trot and canter but no significant improvement was observed at the walk or while turning 5 Causes edit nbsp Hypochaeris radicata flatweed is linked to some cases of stringhalt in horses The most common plant species that have been found and identified in pastures where affected horses were located include flatweed Hypochaeris radicata sheep s sorrel Rumex acetosella and couch grass Elymus repens The type of nerve damage sustained in horses with Australian stringhalt suggests a mould toxin mycotoxin or a fungal poison found in the soils may be a cause for this condition Mycotoxins can directly affect the long myelinated nerves in the hind limbs 2 See also editMuscular system of the horse Scotty cramp a condition in dogs that may resemble stringhalt in horsesReferences edit James Rooney Stringhalt The Lame Horse Horseshoes com Retrieved 1 July 2007 a b c d e f g Huntington PJ Jeffcott LB Friend SC Luff AR Finkelstein DI Flynn RJ July 1989 Australian Stringhalt epidemiological clinical and neurological investigations Equine Veterinary Journal 21 4 266 73 doi 10 1111 j 2042 3306 1989 tb02165 x PMID 2767028 a b c Slocombe RF Huntington PJ Friend SC Jeffcott LB Luff AR Finkelstein DK May 1992 Pathological aspects of Australian Stringhalt Equine Veterinary Journal 24 3 174 83 doi 10 1111 j 2042 3306 1992 tb02810 x PMID 1606929 Cahill JI Goulden BE Jolly RD September 1986 Stringhalt in horses a distal axonopathy Neuropathology and Applied Neurobiology 12 5 459 75 doi 10 1111 j 1365 2990 1986 tb00054 x PMID 3024050 S2CID 26816155 a b Huntington PJ Seneque S Slocombe RF Jeffcott LB McLean A Luff AR July 1991 Use of phenytoin to treat horses with Australian stringhalt Australian Veterinary Journal 68 7 221 4 doi 10 1111 j 1751 0813 1991 tb03210 x PMID 1929987 Retrieved from https en wikipedia org w index php title Stringhalt amp oldid 1137189094, wikipedia, wiki, book, books, library,
