PHOTOSENSITIZATION IN SHEEP FED AMMI-MAJUS (BISHOPS WEED) SEED

Abstract

A. majus (bishop''s weed) grows on the coastal region of southern USA and in other parts of the world. This plant causes severe photosensitization in livestock and probably contributes to the severe photosensitization outbreaks seen in Texas. Sheep were fed finely ground seed of A. majus via stomach tube at dose rates of 1, 2, 4 and 8 g/kg of body weight and exposed to sunlight. The single dose of 8 g/kg produced severe clinical signs (in 24-48 h): cloudy cornea, conjunctivokeratitis, photophobia and edema of the muzzle, ears and vulva. Daily dosing at 2 and 4 g/kg produced (in 72-96 h) similar signs; the smallest dose (1 g/kg) produced mild irritation of the muzzle. Pathologic changes included corneal edema and marked neutrophilic infiltration of the cornea and corenal/ciliary process; subacute ulcerative and exudative dermatitis of the skin of ears, muzzle and vulva; and mild focal tubular degeneration (vacuolar type) of the kidney.