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This article was published in 1954
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.

Algal Poisoning in Livestock

E. J. McBARRON, B.V.Sc., P.P. Board Veterinary Research Officer, Glenfield.

Because of the widespread nature of algae (scum or waterbloom) throughout the waters of the globe, it is surprising that more records are not available of their toxicity to animal life. The following review, based mainly on overseas work, is presented in the hope that more attention might be given to it.

In fresh water the algal flora is mainly a mixture of blue-greens, greens and yellow-green types. In salt water, the seaweeds belong to the red and brown types. The green and blue-green appear to be the commonest class in cases of stock poisoning, especially the genus Microcystis.

Steyn (1945) has given an exhaustive review of poisoning of sheep and cattle by Microcystis sp. at Vaaldam, South Africa. During calm and warm weather the algae float on the surface of the water but in boisterous and stormy weather the plants are dispersed in water, sometimes to a depth of twenty feet. The growth is favoured by abundant sunlight, warm conditions and the presence of rotting vegetation and organic matter. As well as these conditions, histories of stock losses invariably include a breeze blowing from one direction which tends to concentrate the algae at the margin of the reservoir from which the stock drink.

The Vaaldam algae exhibited a toxic substance affecting the central nervous system and the liver; together with a substance producing photosensitisation.

In peracute cases the liver cells were destroyed within a few hours. Symptoms similar to strychnine convulsions were seen and death occurred within a few hours. The acute and sub-acute cases lingered from 1-2 weeks and exhibited jaundice and photosensitisation on the hairless portions of the skin. Chronic cases may remain sick for weeks or months.

Post-mortem lesions in peracute cases include a very friable liver, approaching to a consistency of porridge; and congestion of the lungs.

Stewart et al. (1950) describe poisoning of cattle in Canada by Microcystis growing on a lake. Muscular twitchings and stiffness were present, but neither bloating nor convulsions. One subject drenched with six gallons of the suspected water died within twenty-five minutes. Post-mortem showed a swollen and mottled liver, while histological examination revealed changes in the lungs, heart, liver and kidney.

SUSPECTED CASES OF AGAL POISONING IN NEW SOUTH WALES

Hurst (1942) records Hyalotheca sp. in the Casino district and Microcystis sp. from the Forbes district.

In 1953 a water sample was received from a 10,000 yard tank at Oakland in the Urana district. It had the appearance of green paint. This was suspected of poisoning 60 ewes out of a mob of 480; 57 dying within 24 hours, after prevailing winds had concentrated the algae on one side of the tank. The algae was identified as Gleocapsa sp. from the blue-green group. Feeding tests, however, proved negative, but deaths ceased after removal from the suspected tank.

In February, 1939, a green scum from a PWP in the Hillston district was identified as Aphanocarpa sp. The water gave off an offensive odour and "drover's horses and sheep would not drink the water".

One might speculate as to whether the alleged photosensitisation effects of the semi-aquatic "Smart Weeds" (Polygonum spp.) are not due to the ingestion of algae from the adjacent drinking places.

SPECIMENS FOR LABORATORY EXAMINATION

The difficulties of obtaining laboratory confirmation in algal poisoning are summarised by Stewart et al. (1950):-"The dependence upon field sources of toxic material" and the rapid disappearance "due to the changeover in the algal flora". A quantity of the suspected water - up to ten gallons - is required; with a small amount containing 3 per cent. formalin. Material from the lungs, liver, heart and kidney, suitably preserved, should be sent, together with fluid ingesta preserved by formalin.

References

Hurst, E. (1942).-"Poison Plants of N.S.W.", Sydney.
Stewart, A. G. Bernum, D.A. and Henderson, J. A. (1950.-Canad J. Comp. Med. and vet. Sci., 14 : 197-202.
Steyn, D. G. (1945).-"Poisoning of Animals by Algae (Scum or Waterbloom) in Dams and Pans", 9pp. Gov. Printer, Pretoria.