Livestock owners should be aware that seasonal conditions are ideal for blue-green algal growth in farm water supplies, resulting in poisoning of livestock and pets.
Victoria’s Acting Chief Veterinary Officer, Dr Cameron Bell, said blue-green algae poisoning was usually seen in late summer and early autumn.
He said blue-green algal blooms typically appeared as surface scum like a suspension of green paint or curdled green milk, with colour ranging from pale green to dark brown, often accompanied by an ‘earthy’ smell.
“Deaths occur when stock drink toxins produced by the blue-green algae, often when it is concentrated on the down-wind side of a water supply and has formed a dense, surface scum.
“Animals that have consumed blue-green algal toxin may become ill very rapidly and die within 24 hours. Those that don’t die immediately often suffer severe liver damage. This may lead to the development of jaundice (the yellows) or photosensitisation over the next few days.”
Dr Bell said animals that recovered from these ailments may then suffer from chronic ill-thrift and there was no specific treatment for blue-green algae poisoning.
“Blue-green algal poisoning should be suspected when animals are found dead and dying after access to an algal-contaminated water source. Dead animals may have their mouths, nose, feet and legs stained green by algae,” he said.
Laboratory testing of water for blue-green algae, and a post-mortem examination of dead or sick animals by a veterinarian, will confirm blue-green algal poisoning.
“Checking stock water supplies daily for blooms remains the most effective way of preventing stock deaths.”
Dr Bell said another way to help be prepared was to develop a livestock water budget to identify how much stock water was required per day.
Also allow for high consumption during the current hot conditions and identify an alternative water supply prior to the primary source of livestock drinking water being affected by a bloom.
If a suspicious bloom is noticed, stock should be removed from the contaminated water source as quickly as possible, and a safe alternate water supply provided.
Blue-green algae toxins may also remain on dry pasture for some time following irrigation, and so stock should be kept off pasture irrigated with blue-green algae-contaminated water for at least seven days after irrigation.
Dr Bell said dogs were prone to poisoning as they tended to swim in farm water supplies and should be excluded from suspect water sources.
Accurate identification of algae should be sought first.
“If chemical water treatments are used, manufacturer instructions should be followed closely, as even more toxin may be released into the water supply as the algae die.
“This potentially makes the water even more toxic, and livestock should be removed from the water source until toxin is no longer present.”
Visit www.agriculture.vic.gov.au/agriculture/farm-management/blue-green-algae-issues for more on blue-green algae contamination in your irrigation water source or livestock water supply.
For further advice please contact your local veterinarian or Agriculture Victoria Veterinary or Animal Health Officer, or in NSW, your Local Land Services.