If your horses pick their back legs up very high and walk in a peculiar exaggerated fashion, are unable to move, and there is wasting of thigh muscles, then they might have stringhalt. The Australian stringhalt occurs in outbreaks in Australia, New Zealand, California and Washington states, is associated with grazing of poor quality pastures containing the weed Hypochaeris radicata.
Hypochaeris radicata, or common catsear, also called flatweed and false dandelion, is a perennial weed primarily of turfgrass and lawns that resembles dandelion. Found in the eastern United States as far north as New Jersey and as far west as Mississippi. It contains unknown toxin which causes degeneration of the nerve tissue, especially of the larger myelinated fibers and neurogenic muscle atrophy. With early diagnosis and treatment, some horses may recover while others,
more severely affected, may not.