CURRENT seasonal conditions across much of eastern Australia remain favourable for blue-green algae to thrive in farm water supplies over summer, and livestock owners are being reminded of the need to remain alert, over potential poisoning of livestock.

Landholders are taking the opportunity provided by severe drought conditions to desilt dams.

“As there is no specific treatment for blue-green algae poisoning, producers should check farm water supplies daily for blooms, as this remains the most effective way of preventing stock deaths,” Victoria’s acting chief veterinary officer, Dr Cameron Bell said.

Blooms typically appeared as surface scum that looks like a suspension of green paint or curdled green milk, often with an earthy smell. However, the colour may range from pale green to dark brown.

Deaths can 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 appear ill very rapidly, develop a staggery gait, collapse, begin to convulse and die – typically within 24 hours – depending on the toxicity of the bloom and the concentration of the toxin. Those that do not 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 recover from these ailments often suffered from chronic ill-thrift.

“If a suspicious bloom is noticed, stock should be removed as quickly as possible, and a safe alternative water supply provided,” he said.

“Where possible producers should identify an alternative water supply, prior to their primary source of livestock drinking water being affected by a bloom. There may not be time to identify an alternative water source once the primary water supply is affected,” Dr Bell said.

“We recommend laboratory testing of the water supply for the presence of blue-green algae, and a postmortem examination of dead or sick animals by a veterinarian.”

Blue-green algae toxins may remain on dry pasture for a long time following irrigation, often until there is a rain event or further irrigation with uncontaminated water. Contaminated water should not be used to irrigate vegetables and fruit or come in contact with plants being grown for food.

It is also recommended to keep stock off pasture that has been irrigated with blue-green algae contaminated water for at least seven days after irrigation. Dr Bell said dogs were also prone to poisoning as they tended to swim in farm water supplies and should be kept away from suspect water sources.

• Information on blue-green algal contamination in stock water supplies or irrigation water sources is available here.