What to look for
- Abortions, stillborn & deformed calves
- The type of deformity varies with the age of the foetus when it was infected – the brain is the main site in earlier pregnancy and the legs and joints can be affected in later pregnancy.
- No signs of illness in adult cattle
Cause – an insect-borne virus
Akabane virus is carried by biting midges called Culicoides, which range over large regions of tropical and sub-tropical Australia. Cattle in this area are regularly exposed to akabane virus, leading to a high level of immunity. Problems occur when Culicoides midges spread into areas where Akabane virus has not appeared for a number of years, so the cattle population has little immunity. If cows are 3-6 months pregnant when infected multiple cases of abortions, stillbirths and deformed calves may occur.
Animals likely to be affected
Pregnant animals < 2 years old.
Other diseases with similar signs
Other causes of abortion and stillbirth. Other causes of deformity in calves exist, which are sometimes very hard to diagnose.
Confirming the diagnosis
Tests on foetal fluids or the blood of the dam, together with a history of Culicoides midges in the area when the cows were in mid-pregnancy.
Risks to people
No direct risk however abortions in cattle are caused by a number of other infections, some of which cause diseases in people, so pay close attention to personal hygiene if handling aborted calves or their mothers.
Treatment is not necessary. Cows that have been infected with the virus become immune and can be expected to have normal fertility in future (unless a major intervention was needed to deliver an aborted calf).
- Abnormal weather conditions favouring spread of Culicoides midges
- Introducing pregnant animals from southern regions into areas where Culicoides midges are active and carrying Akabane virus.