Water

Blue-green algae alert

By Country News

Livestock owners are being reminded to be vigilant and remain on the alert for blue-green algae poisoning.

Usually seen in late summer and early autumn, Victoria’s chief veterinary officer Charles Milne said the current seasonal conditions remained typical for blue-green algae to thrive in farm water supplies.

‘‘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,’’ Dr Milne said.

‘‘Blue-green algal blooms typically appear 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.’’

Dr Milne said deaths could occur when stock drank toxins produced by the blue-green algae, often when it was concentrated on the downwind side of a water supply and had formed a dense surface scum.

He said animals that had consumed blue-green algal toxin might 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 did not die immediately often suffered severe liver damage which might lead to the development of jaundice (the yellows) or photosensitisation in the next few days. Those that recovered from these ailments often suffered from chronic ill-thrift, Dr Milne said.

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

‘‘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 Milne said.

‘‘We recommend laboratory testing of the water supply for the presence of blue-green algae, and a post-mortem 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, particularly fruit and vegetables that are mostly eaten raw such as apples, grapes, tomatoes, strawberries, cabbages and other salad greens.

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, with Dr Milne also reminding farmers that dogs are prone to poisoning as they tend to swim in farm water supplies and should be kept away from suspect water sources.