Akabane

Overview

Cause

Akabane virus is an arbovirus in the bunyavirus family.

Description

This is primarily a disease of cattle, causing deformities in the foetus. Rarely, deformities in lambs have been recorded. Other species may become infected without apparent signs of disease, including buffalo, camels, horses, goats and dogs.

Where the disease occurs

Akabane virus, named after the district in Japan where it was first found, also occurs in Korea, Israel, central Africa and Australia. It causes disease sporadically in Queensland.

The disease in animals

Akabane virus infection of animals results in a transient viraemia with a subsequent antibody rise but no clinical signs are seen. It affects the nervous system of the foetus in pregnant females.

In calves born alive, the disease appears in three forms:

  • Calves infected at an older foetal age (5-6 months) are born with arthrogryposis (fixation of joints in the limbs and spine due to the failure of muscle development). These skeletal deformities are seen first in an outbreak.
  • Earlier infection results in calves born with arthrogryposis and hydranencephaly (deficiency of cerebral cortex and replacement of brain tissue by a fluid-filled sac).
  • Calves affected at 3-4 months foetal age show hydranencephaly only.

There may be calving problems with arthrogryposis calves due to calf limb deformity. When born alive they are fully mature with regards to teeth, coat and hooves, but are small, underweight, weak and often unable to stand. Calves with hydranencephaly can rise and walk, but are blind, have no basic reflexes and lack 'intelligence'.

Diagnosis

Diagnosis can often be made on the basis of the clinical signs and can be confirmed by demonstration of antibody in the blood of calf or dam.

Spread of the disease

The disease is transmitted by blood-feedng insects, mostly Culicoides brevitasis (midges) but other vectors could exist. Normally in areas where the midge is present, no signs of the disease are seen because the dams have been infected prior to their first pregnancy and are immune. When suitable weather conditions allow the midges to extend their normal range into areas with susceptible animals, and these animals have not previously been infected, clinical signs may be seen in the next calving season.

Control of the disease in animals

There is no successful treatment or means of control because of the nature of lesions and method of disease spread. If an area is known to be endemic, breeding stock should be introduced to the area at an early age to gain immunity prior to joining.

Can people get the disease?

The virus does not affect humans.

Last updated 27 May 2013