Following verified cases in cattle herds near Gilgandra and potential cases reported in Forbes, vets expect the disease to move south through the region.

The virus, transmitted by insects, induces high fever as well as pain in the muscles and joints, and has the potential to cause serious economic and production losses.

In recent days cases have also been reported in the Hunter and Mid North Coast regions.

Central West Local Land Services district veterinarian Alicia Moses, Grenfell, said the onset of clinical signs is usually rapid with bulls and fat cows typically the worst affected.

"Clinical signs include fever, muscle stiffness, recumbency, swelling of joints, drooling and nasal and ocular discharges," she said.

"Severely affected animals lose condition and pregnant cows may abort.

"In most cases the infection has a short duration with rapid recovery, however occasional deaths are reported."

The LLS recommends providing affected cattle with shade and water, and feed once they regain an appetite.

Cattle unable to get up after a day or two should be turned or lifted at least twice daily to prevent secondary nerve and muscle compression.

Long term effects of three-day sickness can become an issue when bulls are infected.

The prolonged fever affects sperm production and quality which can cause transient infertility.

The LLS recommends the semen testing of bulls three-to-six-months post infection or prior to their next joining by a vet.

Dr Moses said there are several diseases that may resemble three-day sickness requiring alternative treatment, so veterinary diagnosis is essential.

"Treatment with anti-inflammatories has been shown to reduce the course of the disease," she said.

"Most animals will recover if supportive treatment including shade and water is provided.

"Proactive programming aimed to minimise insect bites will go a long way for mitigating the problem.

"A combination of pour on products and insecticidal ear tags are helpful in reducing insect burdens.

"A vaccine is available, and its use is recommended for higher value animals or introduced cattle from areas which do not normally experience the virus. In areas where the virus is already active the vaccine is unlikely to provide protection."

Recently recovered cattle should not be sent to the abattoirs for several weeks to give the body a chance to heal and avoid the possibility of downgrades from any residual muscle damage.