Bovine abortion caused by Listeria ivanovii

Listeria ivanovii was described in 1984, having been isolated from aborted ovine foetuses. It had been formerly known as Listeria monocytogenes serotype 5. However, it differs from L monocytogenes by production of a wide, clear or double zone of haemolysis on sheep or horse blood agar, a positive CAMP reaction with Rhodococcus equi but not with haemolytic Staphylococcus aureus and fermentation of D-xylose but not L-rhamnose. In Australia, L ivanovii has been associated with outbreaks of neonatal death or sporadic abortion of sheep but not cattle. Alexander et al described four sporadic cases of bovine abortion due to L ivanovii in four herds in California; a bovine case had previously been reported in New Zealand. During 1988 to 1995, we confirmed eight cases of bovine abortion due to L ivanovii on six widely dispersed farms in New South Wales. Outbreaks of listeriosis in sheep are often associated with periods of cold and wet weather, nutritional stress and sometimes the feeding of silage. Bagged silage had been fed to the Wingham herd, otherwise, no predisposing factors could be found. None of cattle grazed with sheep. The pathogenesis is unclear. The bronchopneumonia suggests spread from the placenta to the foetus via the amniotic fluid. Listeria can be excreted in the milk of infected cows, risking spread to calves or people who consume raw milk or milk products.