The Hunter Local Land Services said laboratory testing had confirmed the disease in cattle near Wingham and Gloucester in recent days. Cases have also been reported at Cooloongolook, Stroud, Dungog, Gresford and Seaham.

The virus, which is transmitted by insects, causes a high fever and pain in the muscles and joints. Cattle that have previously been exposed will have developed an immunity to the disease. Locally-bred cattle under two years old are at the highest risk. Cattle of any age which have been brought into the area from southern and western parts of NSW or from Victoria, Tasmania or South Australia, where immunity from previous exposure is unlikely, could also be affected.

Hunter LLS district veterinarian Lyndell Stone said sick cattle were often by themselves, off their feed, seeking shade and water, shivering, drooling and could show signs of lameness. "These signs usually last only a few days and most cattle recover uneventfully. However, reports from Queensland, where the disease was seen earlier in the season, suggest that cases this year seem to be more severe," Dr Stone said.

Some cattle, especially bulls and heavier conditioned cattle, may go down and take several days to get back on their feet, increasing the risk of secondary complications. Pregnant cows may abort and bulls may become infertile for up to six months. Milk production can drop significantly in lactating cows.