Bovine Ephemeral Fever (BEF) is also called as Three Days Sickness caused by an Arboovirus and transmitted by flying, biting insects (most likely mosquitoes), affecting the cattle and occasionally buffaloes. It is mostly sporadic in hot and humid areas. Outbreaks of disease occur during or after periods of heavy summer rainfall as it is most prevalent in the wet season in the tropics and in summer to early autumn in the subtropics or temperate regions. The BEF virus can survive in winter on vectors. It is a transboundary disease that may spread from one country to another by wind and live animal trading.
Cause:
An arthropod–borne Arbovirus known as ‘ephemeral fever virus’ or ‘bovine ephemeral fever virus‘. It is a banded mosquito, Culex annulirostris, is a vector of BEF virus.
Signs & Symptoms:
There are typically 3 recognized stages of bovine ephemeral virus. The acute febrile stage appears suddenly and is especially noticeable in dairy cattle. The second stage is muscular stiffness and lameness in 1 or more limbs. Some secondary bloat may occur due to general inflammation of the abdominal cavity and ruminal stasis. Lameness may shift between limbs and joints may be visibly swollen.
During recovery, most affected animals resume eating and drinking. Animals may go down, with heavy animals in good condition being most affected. Some animals remain down due to muscle damage or damage to the spinal cord from constant struggling. Animal shows the signs of:
- Rapid and significant decrease in milk production.
- Rapid onset of fever from 101°F to 105°F. Within 36 hours, the temperature returns to normal levels.
- Lactating cows can dry up completely
- Heavily pregnant cows in advance stage may abort (This is more likely due to the fever than a virus-specific impact).
- Animals quit eating and drinking and develop depression
- Affected animals may shiver, become very stiff with shifting lameness and are reluctant to move.
- Occasional deaths (3%) or prolonged recumbency leading to ‘downer syndrome’ can occur.
- Temporary or permanent paralysis may occur as a result of damage to the spinal cord
- The joints may appear swollen and sometimes there is swelling around the jaw.
- Typically drooling of saliva
- The virus can affect the nerves that control swallowing. This means that affected animals are at risk getting food, water or saliva into the lungs. This can result in pneumonia.
- Produce stringy nasal discharge
- May have watery eyes
- Male bulls may be temporarily infertile (up to 8 weeks).
Diagnosis:
When an outbreak occurs in unvaccinated cattle not previously exposed to the virus, a diagnosis of BEF can often be made based on clinical signs and the brevity of illness. However, when most animals are immune and occasional cases occur, or when there are cases in areas where the disease occurs less frequently, laboratory confirmation of the cause of illness may be required. The BEF disease diagnosis is based on various serological tests, serum neutralisation and a blocking ELISA analysis.
- A Bovine Ephemeral Fever Virus Antibody (Anti-BEFV) ELISA Kit used for the qualitative detection of BEFV in the bovine serum.
- Virus neutralisation (VN) test
- A blocking ELISA analysis
- Reverse transcriptase (RT)-PCR amplification
Treatment:
- Nursing care- Animals that have gone down should be provided with adequate shelter, water and food, as cattle left exposed in hot weather are much more likely to die. BEF can impair the swallowing reflex, so affected animals should not be drenched or force fed.
- Handled stock benefit from being rolled over several times a day to help avoid loss of circulation to the underside limbs, which will result in permanent muscle damage. The heavier the animal is, the more critical it is to get it back on its feet as quickly as possible. However, for unhandled stock, constant handling such as rolling or attempts to relocate may adversely stress.
- Anti-inflammatory drugs are recommended for recumbent animals and would be useful for clinically affected animals.
- Calcium injections- if given early in the course of the illness, can be very effective in helping an animal regain its footing.
Prevention:
- There is a modified live vaccine for prevention of BEF that provides long-lasting protection. To achieve long lasting protection, two doses are required. The ideal is to give the first dose before disease occurs in the district. The second dose is then given at least four weeks later, and as close as possible to when disease is likely to commence in the district. The second dose can be given up to 6 months after the first dose. Animals can be vaccinated from six months of age and should then be revaccinated each year, at the start of summer, to ensure continued protection.
- Proper fly control would help to reduce the disease.
- Complete rest is the most effective treatment. Recovered animals should not be stressed or worked for some days since relapse may occur.
