BOVINE EPHEMERAL FEVER (BEF)
Bovine Ephemeral Fever (BEF) is a viral disease of cattle and buffalo that has become established now in parts of eastern Australia. BEF is commonly known as the ‘Three Day Sickness’ as affected animals are sick only for a few days.
BEF is spread by biting insects, usually mosquitoes and midges and most commonly occurs between January and April, with the greatest number of cases in March. However, cases can occur from December through to early June. Cases in the winter or spring months, even in coastal districts, are rare.
SIGNS OF BEF TO WATCH FOR
· If your animals experience a sudden onset of fever- as high as 41oC and then returns to normal within 36 hours.
· The first sign in milking cows is a sudden and severe drop in milk production.
· Cows in advanced pregnancy may abort.
· Animals stop eating and drinking and become depressed. They usually drool saliva, develop a stringy nasal discharge, and may have watery eyes.
· Affected animals may shiver and often become very stiff with a shifting lameness, and are reluctant to move. Note, Lameness may not become apparent until the second day of illness.
· The joints may appear swollen and sometimes there is swelling around the jaw. Some animals - particularly the heavier ones - just lie down and refuse to move.
· By day three the affected animal is usually standing again and will begin to eat. However, lameness and weakness may last for another two or three days.
· In the clear majority of cases the disease runs a short course, followed by rapid and complete recovery. However, the disease can vary in severity. Some animals may show only slight symptoms for about 24 hours, while a small number may stay down for many weeks. The disease is usually milder in calves under 12 months of age.
· Milk production usually drops by at least 50% in sick cows. In dairy herds, it is the highest producing animals that are usually the most severely affected. Yield should return nearly to normal after about three weeks, but cows affected late in lactation often dry off. Mastitis sometimes develops, with a marked rise in the somatic cell count.
· Bulls and fat cows tend to show more severe signs than other cattle. Such animals lose condition rapidly and are slow to regain their body weight. A proportion of bulls will suffer temporary infertility lasting from three to six months because of the high fever. Permanent infertility is uncommon but can occur.
· A small proportion of animals that go down may suffer a permanent paralysis due to damage to the spinal cord- either as a direct effect of the virus, or due to injuries if they fall awkwardly.
· Although most of the herd can be affected, deaths from ephemeral fever are uncommon and rarely involve more than 1% of the herd. Death is usually the result of misadventure or being down for a long period.
When an outbreak of BEF 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, laboratory confirmation of the cause of illness may be required. Usually this is done by taking two blood samples - one during the very early stages of the illness, and another three weeks later. If BEF is responsible, BEF antibody levels will be much higher in the second test than in the first.
Medical treatment is often unnecessary for non-lactating stock. However, bulls and high producing cows in early to peak production should be treated promptly and given a calcium injection to help them to rise.
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.
They infected cattle should be 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.
The use of anti-inflammatory drugs is recommended for any animals that become recumbent, and would be useful for any clinically affected animals. This treatment is only available through veterinary prescription. Long withholding periods may apply to some anti-inflammatory drugs, so read the label carefully.
BEF can impair the swallowing reflex, so affected animals should not be drenched or force fed. This may result in the inhalation of food or water, which can cause pneumonia.
Both live and inactivated vaccines against BEF are available.