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Livestock owners warned on seasonal blue-green algae poisoning risk

by Sheep Central, 12 February 2018

Blue-green algae. Photo – Agriculture Victoria.

LIVESTOCK owners have been urged to be alert for the possibility of blue-green algae poisoning, following the recent stretch of hot weather.

Agriculture Victoria district veterinary officer Dr Jeff Cave said said blue-green algae poisoning is usually seen in late summer and early autumn.

Toxic blue-green algal blooms have the potential to kill large numbers of stock in a very short period of time. They typically appear as surface scum that looks like a suspension of green paint, or curdled green milk. However, the colour may range from pale green to dark brown. Often an ‘earthy’ smell will accompany a blue-green algal bloom.

In comparison, other algal blooms may look like green mats, and can be pulled from the dam in long strings and typically have no smell.

Dr Cave said deaths occur when stock drink the toxins produced by the blue-green algae, usually from where they are concentrated on the down-wind side of a water supply in a dense, surface scum.

Animals that have consumed blue-green algal toxin will appear ill very rapidly, they will develop a staggering gait, collapse, and then begin to convulse and die – typically within 24 hours.

Those that do not die immediately usually suffer severe liver damage. This may lead to the development of jaundice (the ‘yellows’) or severe photosensitisation over the next few days.

Dr Cave said those that recover from these ailments will suffer from chronic ill-thrift. Unfortunately there is no treatment for affected animals.

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.

Dr Cave said 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 will confirm blue-green algal poisoning.

Therefore, it is essential stock water supplies are checked daily for blooms, as this remains the most effective way of preventing stock deaths, he said. If a suspicious bloom is noticed, stock should be removed from the contaminated water source as quickly as possible, and an accurate identification of algae should be sought.

Chemical water treatments that cause algal cells to break down or die are not recommended, as these treatments allow the release of pre-formed toxins into the water. This potentially makes the water even more toxic to stock.

For further Information please go to our website http://go.vic.gov.au/TATbyT or contact your local veterinarian or Agriculture Victoria veterinary or animal health officer, or in NSW your Local Land Services.

Source: Agriculture Victoria.

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