Virulent footrot has been detected in Western Australia, with a ram imported from the eastern states testing positive to the reportable disease.
The Department of Primary Industries and Regional Development (DPIRD) said the infected ram was identified through routine post-border inspections of sheep and goats entering WA from interstate.
The department said it was now tracing all of the sheep that travelled in the same truck as the infected ram.
It said it had traced sheep to multiple properties across Western Australia and was testing sheep at those properties.
Footrot is a bacterial infection that causes painful lesions in sheep and goats, making them lame, lose weight and produce less wool.
The contagious disease is classified as benign or virulent according to the severity of symptoms caused in infected animals.
The virulent strain is confined to one per cent of West Australian agricultural properties.
In a statement it said the property which received the animal was currently under a pest control notice, restricting movement of sheep and goats until the infection is eradicated.
It is understood properties involved in the contact tracing have also been placed under quarantine notices.
The department said it was not able to advise the location or number of properties affected.
Warm, moist conditions cause the bacteria to spread rapidly with lesions forming on the feet of infected animals.
In a statement, DPIRD said the producer with the infected ram had followed all the recommended biosecurity protocols, including keeping any imported animals separate from the home flock.
Currently 17 cents from the sale of every sheep and goat in Western Australia is used to fund biosecurity activities including the control of virulent footrot.