Australian Stringhalt–epidemiological, clinical and neurological investigations.

The research article discusses a detailed investigation carried out on 78 cases of a muscle disorder in horses known as Australian Stringhalt, primarily found in Victoria from 1985 to 1987. The study illustrates the common conditions where the disease arises, describes the range of clinical symptoms observed, and suggests grading to classify the severity of the disease.

Investigation Details

• The researchers studied 78 cases of Australian Stringhalt in horses from 52 properties in Victoria over three years.
• The study involved horses in different scenarios. Some horses were examined directly on the field (52 cases), others were brought to a Veterinary Clinical Centre (13 cases), and the remaining 13 cases were investigated through verbal exchange of clinical details.
• In addition, 10 cases of false or atypical stringhalt were evaluated to differentiate from typical cases.
• The team also focused on the soil and pasture conditions in 14 properties where a case of Australian Stringhalt had been reported.

Epidemiology and Environment

• A detailed survey was conducted to identify the common properties associated with the disease among practitioners.
• 50 out of the 52 field-examined cases occurred in horses which had been feeding on unimproved dry pasture of poor quality.
• Most properties lacked fertiliser and pasture improvements, leading to the proliferation of weeds, especially flatweed or Hypochaeris radicata.

Clinical Signs and Grading System

• The research documented the array of clinical signs associated with Australian Stringhalt and proposed a grading system to classify horses according to the severity of the condition.
• The study observed laryngeal abnormalities in 10 out of 11 cases under endoscopic examination.
• Increased electromyographic (EMG) activity was noticed at rest and during hindlimb flexion in horses displaying laryngeal abnormalities.
• Changes in electrical activity and improvements for muscle loss were monitored in recovering horses, pointing out the jerkiness as a potential symptom of Stringhalt.

Nerve Conduction Studies

• In four horses with the ailment, nerve conduction studies showed a drastic reduction in the speed of nerve impulses, particularly when stimulated at a frequency of 50 Hz.
• These horses failed to maintain the activation of the long digital extensor muscle, indicating a nerve disorder partly responsible for abnormal hindlimb movements.

The research concludes that EMG and evoked responses could serve as significant indicators for the state of Australian Stringhalt in horses.