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Stringhalt in Horses and the Role of Mycotoxins

Stringhalt in Horses and the Role of Mycotoxins

Stringhalt is a neurological condition in horses characterised by the involuntary and exaggerated hyperflexion of the hock joint during movement. This abnormal gait most commonly affects the hind limbs, with one or both legs potentially involved. While the upward movement of the limb is exaggerated, sometimes so severe that the fetlock touches the abdomen, the downward motion remains normal. The intensity of the gait can range from mild to severely disabling. 

Types of Stringhalt in Horses 

 There are two main forms of stringhalt, each with different causes and geographic tendencies: 

 1. Classic (North American) Stringhalt 

  •  Typically affects a single horse and often only one limb 
  •  Usually occurs after trauma or injury to the leg Involves the lateral digital extensor muscle tendon 
  •  Spontaneous recovery is rare, though some improvement can be seen with rest 
  •  Can occur anywhere globally 

 2. Australian Stringhalt 

  •  Occurs in outbreaks and often affects multiple horses in the same area 
  •  Typically involves both hind legs
  •  Predominantly seen in Australia and New Zealand 
  •  Strongly associated with toxic pasture weeds, especially flatweed (Hypochaeris radicata) 

What Triggers Outbreaks of Australian Stringhalt? 

 Australian Stringhalt is closely linked to seasonal and environmental conditions—especially late summer to autumn when pastures are poor in both quality and quantity due to drought or overgrazing. During these times, horses are forced to consume higher amounts of weeds such as flatweed, capeweed, and other broadleaf species. While early research suspected mycotoxins (fungal toxins) as a potential cause—particularly due to seasonal overlap with other plant-based mycotoxic diseases—a 2011 study by the Rural Industries Research and Development Corporation (Publication No. 11/127) found no conclusive evidence of mycotoxins in flatweed samples. This suggests that the toxic compounds may originate from the plant itself, not fungal contamination.  

What Happens to the Horse’s Body? 

 Stringhalt causes toxic damage to the axons (the long extensions of nerve cells) in the peripheral nerves, particularly those in the larynx and gaskin area (upper hind limb). 

This results in: 

  •  Neuromuscular dysfunction of affected limbs
  •  Atrophy (wasting) of muscles in the gaskin region 
  •  In some cases, laryngeal paralysis, especially in Australian Stringhalt 

 Clinical Signs of Stringhalt

  • Exaggerated high-stepping hind limb movement 
  •  Gait abnormalities worsen when backing up or turning
  •  Symptoms often more noticeable after rest 
  •  May be intermittent or consistent 
  •  Laryngeal dysfunction (roaring or noisy breathing) may also be present 

Are Mycotoxins Responsible for Stringhalt? 

 While mycotoxins from fungi on pasture plants were once thought to be a major factor in Australian Stringhalt, evidence remains inconclusive. It's now believed that toxic compounds from flatweed itself may be responsible for the neurotoxic effects. However, the condition shares a seasonal pattern with other mycotoxin-related diseases, suggesting environmental and fungal stressors may still contribute.  Anecdotal reports suggest that horses on capeweed infested pastures exhibited Stringhalt symptoms. When these horses were adminisered with Toxfree Toxin Binder, the symptoms disappeaed. 

Treatment and Recovery 

 There is no proven cure for Australian Stringhalt, but many horses recover spontaneously within weeks to 12 months. Effective management focuses on: 

  •  Removing horses from affected pastures especially those dominated by flatweed or other toxic weeds 
  •  Improving pasture quality and soil fertility 
  • Supporting nerve and muscle recovery through diet and care 

 Does Magnesium Help Treat Stringhalt? 

Despite common use, there is no scientific evidence to support that magnesium supplementation above daily requirements can treat or prevent stringhalt. While magnesium is essential for normal nerve function, stringhalt involves toxic nerve damage, not a magnesium deficiency. The belief in magnesium’s effectiveness may stem from its calming effects on anxious horses or coincidental timing with natural recovery. 

Summary 

 Stringhalt is a neuromuscular condition involving involuntary high flexion of the hind limbs. Australian Stringhalt occurs in outbreaks and is strongly linked to grazing pastures with flatweed, especially after dry periods. The link between mycotoxins and stringhalt in horses in Australia is not fully established but is strongly suspected based on observational and anecdotal evidence. 

Suggestions

Use broad spectrum Mycotoxin binder like Toxfree Toxin Binder to reduce toxin absorption. 


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