Bovine Ephemeral Fever (BEF) is a viral disease of cattle and buffaloes caused by the virus known as the Rhabdovirus.

How is BEF spread?

BEF is transmitted through mosquitoes and biting midges.

Where does the disease occur in Australia?

Episodic outbreaks in subtropical and temperate regions of Australia. The disease occurs in summer months usually between January and April; however, it can still occur between December through to early June. It rarely occurs in winter and spring.

Clinical signs

Infected cattle can show a wide spectrum of clinical signs. Clinical signs include a sudden onset of fever with loss of appetite and increased breathing and heart rate. Affected cattle often shiver and become very stiff and lame on all four legs. There may be severe constipation in some cases and diarrhoea in others, which is caused by reduced rumen function. Watery discharges from the eyes and the nose often occurs.

The first sign in dairy cattle is often a sudden and sharp drop in the milk production. In some cases, lactation may stop completely. The highest producing animals are usually most severely affected. In most of the cases, milk production returns to normal progressively with recovery but the level is always lower than pre-illness. Cows in late stage of pregnancy may abort.

The disease is more severe in adult cattle than in young animal; in fat animals than in lean animals, in heavy bulls than in light steers, in high lactating cattle than in dry cows. Bulls and fat cows loose condition rapidly and regain their body weight slowly after recovery. Calves are least affected, those less than 12 months of age usually show mild clinical signs and calves less than 3-6 months of age are not affected by the disease.

BEF has a short course of 3 days, a complete recovery occurs in 95-97% of the cases regardless of the severity of the clinical signs.

Complications

Recovery is usually rapid and complete unless the affected animals are exposed to extreme weather conditions or aspiration of the stomach content. If affected cattle are without shade and water, they may suffer from severe dehydration.

Occasionally affected bulls are temporary infertile (up to 6 months) because of the high fever. Permanent infertility is uncommon but can occur.

A small proportion of affected animals may suffer permanent paralysis due damage to the spinal cord, either from effect of the virus or injury as the animal goes down.

Deaths from BEF are uncommon, and usually because of misadventure or being down for a long period.

Diagnosis

BEF is usually diagnosed from history and clinical signs. Diagnosis can be made from the sudden onset of fever lasting for 2-5 days followed by spontaneous recovery.

Confirmation of diagnosis can be made by the laboratory either by isolation of the BEF virus or detecting the antibody level. One blood sample can be taken during the fever and isolation of BEF virus from the blood confirms BEF infection. Antibody level can be tested by taking two blood samples, one during the illness and another one two or three weeks later. BEF infected cattle will have much higher BEF antibody levels in the second sample compared to the first.

Treatment

Treatments are usually effective if given in the early stage of the disease. The affected cattle should be rested during the acute phase of the disease. Symptomatic treatment with anti-inflammatory drugs has been found to be beneficial. Various antibiotics can be used if there is a suspicion of secondary bacterial infection.

Animals that have gone down should be provided with adequate shelter, water and food, as cattle exposed to hot weather are much more likely to die. They can be rolled over several times a day to maintain the blood circulation and avoid permanent muscle damage on the down side. It is important to get them back on their feet as soon as possible. Calcium injection can be given as it often helps to get recumbent cattle back on their feet.

BEF affects the swallowing reflex, therefore during the acute phase of illness; no medication should be given orally to avoid inhalation pneumonia.

Control and prevention

In most cases, cattle that have been infected with BEF are resistant to the infection for life. However, some animals, especially older animals may lose immunity after a few years.

Vaccination is the only effective method of control. The modified live vaccine is the commercially available vaccine in Australia. It is available through veterinarians only and can provide protection against BEF for 12 months. Initially, two doses are required 2 weeks to 6 months apart to achieve adequate protection. Animals can be vaccinated from 6 months of age and then have an annual booster vaccine.

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