Secondary photosensitization in a horse on pasture : presumptive alsike clover poisoning

Abstract

The Ambulatory Service was called to evaluate a 2-year old Chincoteague Pony for lethargy, anorexia, and colic. On presentation, the gelding was recumbent with a flaccid lower lip, deviated muzzle, decreased tongue tone, and a decreased menace with normal pupillary light reflexes. The gelding was afebrile with normal gut sounds. Primary differentials at the time included trauma or colic with subsequent facial nerve paralysis; however, causes of brainstem and cranial nerve signs could not be ruled out due to the presence of decreased tongue tone. The following day, the Ambulatory Service was called to evaluate continued signs of mild colic. The second day, ptosis was present on the left eye, the white snip was swollen, edematous, and blistering, and the pony’s sclera and mucous membranes were icteric. The pasture was examined and found to contain alsike clover, Trifolium hybridum.