Feral cats carrying the disease toxoplasmosis are the target of a predator programme that could save Hawke's Bay farmers in excess of $4.5 million dollars a year.
A monitoring programme testing ewes on six farms, as part of the Cape to City predator programme, has found that up to 30 per cent of sheep carry the disease, which causes a high abortion rate in pregnant ewes.
Three "experimental" farms within the 26,000-hectare Cape to City footprint tested feral cats and mice for toxoplasmosis while three control farms outside of the footprint tested mice only.
Sixty sheep on each farm have also been sample tested to form a baseline across the farms that have been matched in size, stocking density and habitat.
Hawke's Bay Regional Council Biosecurity adviser Rod Dickson said the baseline was high but "that was expected" and by reducing feral cats, it is hoped abortion rates will decrease.