BASICS
- Isocoma pluriflora (rayless goldenrod) was previously known as Isocoma wrightii or Haplopappus heterophyllus
- The plant is an erect, bushy, unbranching perennial shrub that grows 60–120 cm (2–4 feet) in height
- The leaves are alternate and linear and generally have a smooth margin but can be toothed; the leaves also may have a sticky feel to them
- The flowers are yellow, tubular, and terminal and number 7–15 per head
- The plant prefers the arid southwest and is found in dry rangelands of southern Colorado, through New Mexico and Arizona, western Texas, and into northern Mexico
- The plant grows well in river valleys, along drainage areas, and is abundant along the Pecos River
- Tremetone, a ketone, is reportedly the toxic agent
- No cases of I. pluriflora intoxication have been documented in horses. However, cases of alkali disease were reported in the early 1900s in horses and is believed to be from I. pluriflora
- The toxin is the same as that found in Eupatorium rugosum (white snakeroot), and presumptive evidence exists that the same clinical signs could be expected—heart muscle degeneration, muscle tremors, ataxia, reluctance to walk, heavy sweating, myoglobinuria, and depression
- Horses that eat E. rugosum have an onset of clinical signs within 2–3 weeks after ingestion; generally, 2–3 days of ingestion is required. Generally this is believed to be approximately 1–2% of their body weight
- The disease has been documented in nursing young of horses, sheep, and cattle
- Affected horses stand with their legs wide apart and develop swelling near the thoracic inlet and along the ventral neck
- There may be a jugular pulse and associated tachycardia
- ECG changes—increased heat rate, ST elevation, and variable QRS complexes
- Cardiac arrhythmias often are present and detectable on auscultation
DIAGNOSIS
TREATMENT
MEDICATIONS
FOLLOW-UP
MISCELLANEOUS