Spontaneous intoxication of cattle by Myrocarpus frondosus in Rio Grande do Sul, Brazil

This report documents the first outbreak of spontaneous hepatogenous photosensitization in dairy cattle due to Myrocarpus frondosus ingestion in southern Brazil. Fourteen of twenty Holstein heifers were affected; one died and was necropsied. Hepatic lesions included periportal and centrilobular necrosis, cholestasis, and bile duct proliferation. Early cutaneous lesions showed uncommon features, such as acantholysis and suprabasilar clefting, contributing to novel histopathological insights that may support earlier diagnosis of hepatogenous photosensitization.