Lythrum hyssopifolia (lesser loosestrife) poisoning of sheep in Victoria.

OBJECTIVE To document an ovine disease attributed to the consumption of Lythrum hyssopifolia (lesser loosestrife). PROCEDURES Historical and histological review of field and experimental cases. RESULTS 1-20% mortality occurred in sheep flocks grazing paddocks where L. hyssopifolia was the predominant green vegetation. Well-documented disease outbreaks occurred in summer on nine farms across Victoria between 1974 and 2002. Liver damage occurred in all nine outbreaks, with kidney damage in at least eight. Hepatocyte necrosis was usually zonal to midzonal (zone 2) in the liver samples from four farms and periacinar (zone 3) in those from three farms, but some livers showed only single-cell necrosis. Multinucleate hepatocytes near necrotic areas were a feature in six cases. Proximal tubular epithelium appeared to be the primary renal target and brown granules were often present in renal tubules. Biochemical and histological evidence of liver and kidney damage was obtained from two sheep experimentally pen-fed harvested L. hyssopifolia. CONCLUSION Chemicals in L. hyssopifolia are toxic to ovine hepatocytes and renal tubular epithelial cells.