Bovine Ephemeral Fever

What to look for

Usually occurs in summer and autumn in the subtropical region of Australia, but outbreaks can occur in southern NSW and northern VIC.

  • Animals suddenly lose their appetite, are depressed and may become very stiff
  • Lactating cows have a severe drop in milk production
  • Most animals make a rapid recovery within a few days, although some take weeks to recover

Cause – an insect-borne virus

The virus is not transmitted from animal to animal directly but carried by several types of mosquitoes that are prevalent in the subtropical region of Australia. In some years the prevailing winds carry these insects into southern NSW and even to Victoria.

Classes of animals likely to be affected

In the subtropical region BEF is most often seen in animals under two years of age but all ages can be infected, especially in regions where animals have little or no immunity.

Confirming the diagnosis

The nature of the outbreak is usually sufficient to allow diagnosis of BEF e.g. several animals are affected with fever and lameness and the initial cases recover in a few days. In areas where the disease does not often occur, laboratory testing may be required.


There is no specific treatment for BEF, but affected animals usually recover in a few days. Animals that do not recover quickly will generally respond to good nursing and provision of shade, water and food.

Risk factors

• weather conditions that spread the carrier mosquitoes from subtropical areas
• introducing animals into subtropical regions from southern regions


When conditions favour the spread of BEF, if may be desirable to vaccinate susceptible stock in areas where the disease occurs less frequently, if severe losses are anticipated.

Do you want animal health info delivered?

Subscribe to Dairy Australia publications