Feral cats carrying the disease toxoplasmosis are the target of a predator programme which could save Hawke's Bay farmers more than $4.5 million a year.

Cape to City is a predator control and ecological restoration programme targeting ferrets, stoats, rats, hedgehogs, feral cats and possums over 26,000 hectare of land between Hastings and Cape Kidnappers. Monitoring of ewes on six farms has found that up to 30 per cent of sheep carried toxoplasmosis, which caused 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.

Hawke's Bay Regional Council biosecurity adviser Rod Dickson said the baseline was high but "that was expected" and by reducing feral cats, it was hoped abortion rates would decrease.

Totally Vets Feilding veterinarian, Trevor Cook said most sheep farmers vaccinated against "toxo" and vets saw very little abortion from it.

"I am sure that blood testing ewes would show many with elevated antibody levels as they respond to the natural challenge. But they respond and there is no disease," he said.

"One vaccination gives life-long immunity. Ewes [and hoggets] are usually vaccinated before they get pregnant."

He said the "live" vaccine was administered carefully at most breeding farms.

Toxoplasma was primarily a parasite of cats, with rodents, sheep and even people becoming infected by ingesting infective stages shed by cats

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