BOVINE EPHEMERAL FEVER

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BOVINE EPHEMERAL FEVER

Nature of the disease
Bovine ephemeral fever (BEF or Bovine Epizootic Fever)  is a non contagious arthropod-borne disease (arbovirus from the Rhabdoviridae family) of cattle, characterised by an acute fever of short duration, with high morbidity and low mortality.
Classification
SPC List D disease
Susceptible species
Cattle and buffalo are believed to be the only significant hosts.
Distribution
BEF occurs widely across Africa and Asia, and in areas of northern and eastern Australia. It does not occur in Europe or the Americas.
Clinical signs 
Onset of clinical signs is usually rapid. Bulls and fat cows or bullocks tend to be worst affected, with calves usually only mildly affected. Clinical signs include:
  • Fever usually lasting only 1-2 days
  • Stiffness, with a shifting lameness affecting one or more legs. Some animals become recumbent and may remain down for up to a week
  • Subcutaneous swelling in the sub-mandibular area or around limb joints
  • Elevated respiratory rate and sometimes dyspnoea
  • Nasal and ocular discharges
  • Drooling of saliva
  • Periorbital swelling
  • Increased excitability and agitation.

 Severely affected animals lose condition, milking cows suffer a severe drop in production and cows in advanced pregnancy may abort. In most cases the infection has a short duration with a rapid recovery. However, occasional cases die and relapses can occur.

Post-mortem findings 
Gross pathology of affected animals is usually unremarkable, with the main findings being: 
  • Oedema of lymph nodes
  • Increased fluid in body cavities and joint cavities, often containing fibrin.
Differential diagnosis 
BEF can be suspected on the basis of its transient nature and rapid spread. In individuals it may resemble conditions such as: 
  • Traumatic reticulitis
  • Acute laminitis
  • Parturient paresis

In early stage 

Specimens required for diagnosis 
Diagnosis is usually made on clinical grounds during major epidemics. Sporadic cases, or those occurring early in a possible epidemic can be confirmed by virus isolation or serology. Paired blood samples should be collected — one during the acute phase, with the second taken 2-3 weeks later.
Transmission   
BEF is spread by infected insects. The virus has been isolated from a range of potential insect vectors, including a number of species of Culicoides and several species of mosquito. There may be a range of vectors involved in spreading the disease, including some that have not yet been identified.
Risk of introduction   
As virus is only present in the blood for short periods during the acute stage of the diseases and as cattle and buffalo are not considered to become carriers, BEF is unlikely to be introduced through the importation of healthy cattle. Infected vectors are an important potential source of introduction. Strong winds can transport vectors long distances, over land and water. Establishment of the disease depends on suitable environmental conditions for the vector to increase and spread.
Control / vaccines  
Animals generally recover quickly without treatment, however the disease is responsive to anti-inflammatory drugs. These drugs must be given for the expected course of the clinical disease. During fever, the paresis or paralysis responds to injected calcium borogluconate in the same manner as parturient paresis (milk fever).

An effective vaccine is available, and can be used to protect animals in the face of an advancing outbreak, or as a routine in endemic areas.

References