Producers should be on the lookout for Akabane in their calving herds this season, with an increased potential risk of losing both cows as well as calves.
Producers should monitor calving herds for Akabane virus affected calves following detection of positive results in sentinel herds and the investigation of reported cases of increased late term abortions and affected calves.
“Routine blood samples are collected from sentinel herds in NSW as part of the National Arbovirus Monitoring Program. Samples collected from both NAMP herds and affected calves at both Glen Innes and Tenterfield have returned positive antibodies to Akabane virus”, said Northern Tablelands Local Land Services District Vet Dr Lisa Martin.
“Affected calves have also been reported from further south (east of Armidale) and are awaiting results.”
Akabane is a virus that is carried by biting midges that generally spread on winds from the north and east of the country. Akabane can cause deformities in calves or late term abortions if a cow or heifer that has not previously been exposed to the Akabane virus, comes in contact with the virus during pregnancy.
The effects of the virus within a herd largely depends on the immune status of the breeder females and the stage of pregnancy at exposure. Cows or heifers that are immune to the virus from previous exposure do not have any pregnancy or fetal problems. Akabane occurs only seasonally on the Northern Tablelands and areas further south.
Infection with Akabane virus late in pregnancy can cause cows to abort, with a higher percentage of pregnancy tested in calf cows failing to produce a calf. Late term infections can also produce calves that appear normal but are uncoordinated. These calves are very susceptible to predation or misadventure.
The classic first sign of an outbreak occurs as the result of calves born with fused joints and flexed legs. The other common presentation with Akabane virus is an enlarged, dome-shaped head as a result of severe brain damage. Calves may appear blind and may wander aimlessly.
“It is normal to see a range in affected calves produced, depending on how long the virus remained around the district and immunity within a herd does vary. We experienced a very mild Autumn and early Winter on the Tablelands which will have favored the midges carrying the virus”, said Lisa.
There is nothing that producers can do to reduce the deformities seen with Akabane virus if your herd is affected. Producers should increase monitoring of calving herds for calving difficulty and provide early assistance to avoid losing cows as well as calves. Even large older cows that you may not routinely monitor can have difficultly delivering calves with bent fused limbs or enlarged heads.
“Fortunately Akabane virus is generally very variable in its range and spread across districts and not all cows in all herds will produce affected calves. Currently we are receiving reports of late term aborted cows and joint affected calves, these should change to more brain affected calves in the next 4 to 6 weeks”, said Lisa.
Producers should also remember Akabane is a virus and not a genetic defect so it is not necessary to cull bulls that produced these calves. Females that have affected calves are also immune against future infections but may end up culled this year just on productivity terms.
For more information contact Dr Lisa Martin on 0428 62 3471 or your nearest Northern Tablelands Local Land Services District Veterinarian.
