Bovine Ephemeral Fever (BEF) is a viral disease of cattle and buffalo. Typically, affected animals are only sick for a few days, hence the alternative name - Three Day Sickness.
What are the signs of BEF?
BEF or three-day sickness is characterised by a fever of short duration which is accompanied by stiffness and lameness. Large numbers of cattle in a herd are affected during an outbreak but deaths do not usually occur.
Severe economic losses occur as bulls, fat cattle and well-conditioned pregnant and lactating cows are most severely affected. These animals will often go down and not be able to get up for three to five days which causes further muscle damage, especially in the heavier animals. Recumbent animals require good nursing care such as provision of food, water and shade. Occasionally they will not get up and will have to be destroyed.
Signs in less severe cases include muscle shivering and weakness, increased respiratory rate and effort, loss of appetite and a sharp fall in milk yield, which immediately follows the onset of fever. The rectal temperature is generally 40.5-41.0°C. Cows in advanced pregnancy may abort by the third day, animals are usually eating and ruminating again and the fever subsides. Weakness and lameness may persist for a further 2-3 days.
How is BEF spread?
BEF is caused by a virus known as a rhabdovirus. It is also referred to as an arbovirus because it is spread by blood-sucking insects, such as mosquitoes (Culex annulirostris) and biting midges (Culicoides spp.). There may also be other carriers that have not yet been identified.
With the onset of warmer conditions in late spring and early summer outbreaks can occur as this is when the populations of these insects are increasing. Spread largely depends on the populations of insects and the force and direction of the prevailing winds.
Where does BEF occur?
Before 1975, the disease occured infrequently in explosive outbreaks every 10-15 years. The outbreaks classically occured in waves originating in the north of Australia in late winter and spring and spread progressively east and southwards, sometimes to Victoria. Large numbers of cattle were affected.
BEF has now become established in parts of eastern Australia, with localised outbreaks occuring on the north coast of NSW, or in the Hunter Valley. Spread may occur from these areas, depending on climatic conditions. Uncommonly, there is a wave of infection moving from Queensland through NSW. The usual pattern consists of sporadic cases for one or two years followed by an outbreak.
Occasional cases have been reported in north-west NSW, usually associated with spread from Queensland. The disease is rare in southern NSW and Victoria, but again, occasional cases have been observed.
When does BEF occur?
Cases of BEF are usually seen between January and April, with the majority occuring in March. However, BEF can be seen as early as December and as late as early June.
Diagnosis of BEF
Cattle are generally immune for one to two years after natural infection. When an outbreak occurs in an unvaccinated herd not previously exposed to the virus, a diagnosis of BEF can often be made based on the clinical signs. Otherwise, blood samples are required to detect a rise in BEF antibody levels. The first blood sample is taken early in the illness and the second 3 weeks later.
No treatment is generally indicated for cattle infected with BEF. However, bulls and high producing cows in early to peak production should be treated promptly.
Anti-inflammatory drugs can be given to reduce the fever and relieve muscle stiffness and soreness. Recumbent animals require good nursing care such as provision of food, water and shade. They should be provided with soft bedding and rolled over several times a day to avoid permanent muscle damage. Cattle with BEF may have difficulty swallowing and oral administration of medicines and water should be carried out with care.
If animals can be detected when their temperature first rises and treated promptly, the signs of the disease can be largely prevented.
How is BEF prevented?
A vaccine is available commercially and can be used to prevent outbreaks. A live attenuated vaccine in freeze-dried suspension is available only by veterinary prescription - the vaccine comes in vials and must be reconstitued with the diluent supplied. The inactivated vaccine is easier to obtain and is cheaper, but only gives about six months protection.
An initial course of two doses, 2 to 4 weeks apart in previously unvaccinated cattle will confer 12 months immunity from 6 months of age. A single dose will not produce adequate protection. Annual boosters are required for all cattle to maintain immunity. A dose of 2ml is given under the skin in the neck. The vaccine has been used safely in cattle in early pregnancy.
Vaccination may not be worthwhile in all cases, depending on production type (beef/dairy), your region's susceptibility to BEF outbreaks and the number of animals to be vaccinated.