A livestock veterinarian says a cattle disease that has spread to South Australia could be devastating when herds are initially exposed.
The tick-borne disease ‘Theileriosis’ has long been present in cattle through parts of Victoria and New South Wales, but was only confirmed on a farm near Millicent SA, this month.
Dr Andrew Whale, of Livestock Logic, says animals that are exposed long-term build up a resistance and are usually unaffected beyond six months of age.
But if stock have never been exposed and are under any form of stress, the result can be catastrophic.
Dr Whale was working in north east Victoria between 2010 and 2012 when an unexpected outbreak occurred.
One farmer was left with 30 dead cattle and another 50 or 60 that could no longer produce milk.
“[The farmer] had purchased about 300 cows from three different properties … a lot of cattle turned up with ticks on them and they spread the Theileria amongst the cattle that hadn’t been exposed,” he said.
“Because they bought cattle that were heavily pregnant, they were under a fair bit of stress and as they started to calve it coincided with the disease outbreak.
“All the stars aligned and we had this terrible outbreak.”
Experts believe the north east Victorian outbreak was the result of two wet summers, which provided ideal conditions for the ticks that carry the disease to flourish.
Dr Whale says this year’s conditions are vastly different and he does not expect a similar outbreak in SA.
“My understanding is that we will not have the bush ticks in the area to cause it to spread and cause significant disease,” he said.
“I suspect that it will be a one-off case, unless there are other people bringing animals from areas that are affected.
“But there have been animals heading backwards and forth between our areas and areas where it is endemic for decades so I don’t see what’s changed now.”
Biosecurity SA has urged cattle farmers in the south east to monitor stock for any signs of the disease, which generally takes effect two to six months after exposure.
“The [disease] kills red blood cells, so [cattle] present with lethargy and really pale mucus membranes,” Dr Whale said.
“They’ll lag behind the mob just through a lack of oxygen.
“Dairy guys will pick up on it in milk production – a real sudden drop in milk production – but I guess the giveaway is you can look at the vulva of an animal and it’s like a ghost, just pale white.”
If cattle appear affected, Dr Whale says they should be dried out and removed from any stressful situation.
Biosecurity SA confirmed farmers in south east SA had brought cattle in from both NSW and Victoria in the months preceding the outbreak but investigations are continuing.
“The means of the disease introduction has not been fully determined and therefore interstate cattle movements may not necessarily be the means of this particular disease introduction,” SA chief veterinarian officer Dr Roger Paskin said.
“It is possible Theileriosis may have been present in the area for some time … or it may have been introduced via wildlife movements.
“The tick responsible for spreading the disease is transported on numerous native species.”
Cattle farmers who suspect infection should contact Biosecurity SA
Source: ABC Rural