Cases of Bovine Ephemeral Fever (BEF) often referred to as three-day sickness have recently been confirmed in cattle herds near Gilgandra.
With potential cases reported in Forbes, it is expected that the disease will move south through the Central West region as the season progresses.
The virus, transmitted by mosquitoes, induces high fever and muscle/joint pain in affected cattle, and has the potential to cause serious economic and production losses.
District Veterinarian Alicia Moses 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."
Long term effects of BEF can be an issue when bulls become infected. The prolonged fever affects sperm production and quality which can cause transient infertility. It is recommended that bulls are semen tested 3-6 months post infection or prior to their next joining by an Australian Cattle Veterinarian.
Ms Moses said there are several diseases that may resemble three-day sickness requiring alternative treatment, so veterinary diagnosis is essential.
"Treatment with anti-inflammatories (available from your private veterinarian) has been shown to reduce the course of the disease.
"Most animals will recover if supportive treatment including shade and water is provided," Ms Moses said.
"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."
For further advice contact your Central West Local Land Services District Veterinarian or private veterinary practitioner.