An outbreak of primary photosensitisation in lambs secondary to consumption of Biserrula pelecinus (biserrula)

An outbreak of photosensitisation affecting approximately 25% of a flock of 120 meat lambs that was grazing a monoculture of the pasture legume Biserrula pelecinus var. Casbah (biserrula) was investigated. Blood samples were taken from sheep with moderate to severe clinical signs, and from apparently normal animals, for a complete blood count and biochemistry; 5 affected animals were subjected to a full necropsy. Histopathological investigation showed lesions consistent with photosensitisation of the exposed unpigmented skin of the face and ears. No histopathological or clinical pathological abnormalities suggestive of a hepatopathy were detected in any of the cases, indicating that the lesions observed in this flock were caused by a primary photosensitising agent present in B. pelecinus. Conclusion: This is the first confirmation that photosensitisation caused by ingestion of biserrula is caused by a primary photosensitising agent.