Toxic plant killing WA sheep

Hundreds of sheep in the Great Southern have died from eating a toxic plant called lesser loosestrife.

The Department of Agriculture and Food (DAFWA) has received reports of poisoning in sheep between Narrogin and Albany, with most reported cases around Kojonup.

Kojonup farmer Les O'Halloran has lost more than 300 six-month-old lambs that were grazing in canola stubble, while Tim Eyres has lost more than 20 orange-tag rams grazing in a pasture paddock.

Mr O'Halloran said lesser loosestrife could be found in just about every paddock.

Many farmers have said they'd never seen the plant before.

The plant, which prefers wet to waterlogged areas, looks similar to rosemary.

It grows 40-60cm high and has leaves that stick out from the stem with small pale pink flowers.

Lesser loosestrife caused widespread deaths last year in Victoria.

Mr O'Halloran said research was needed because not much was known about the plant, including what the toxin is, how long it lasts and how it affects older livestock.

DAFWA veterinarian Jenny Cotter said farmers needed to survey paddocks for the weed and move stock if possible.

Symptoms usually appear 10 days after sheep eat the weed and appear unwell with sometimes mild neurological signs.

"Farmers will notice a tail developing in the flock and on closer examination, will notice animals are not eating and drinking and are becoming quite dehydrated and weak," Dr Cotter said.

Because the toxin affects the liver and kidneys, Dr Cotter said it was important animals were removed from the infected paddock, fed a good-quality hay and low-protein diet for a couple of weeks and given fresh water and shade.

Dr Cotter said deaths could continue for weeks after sheep were removed from paddocks containing the toxic weed.

Where animals are not going to recover, Dr Cotter said it was best to put them down.

Lesser loosestrife is also toxic to cattle.

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Unusual diseases in stock *

If producers suspect they have an unusual disease in their stock and cannot contact their usual veterinarian they can call the Department of Agriculture and Food's Animal Health Laboratories on 9368 3351 (office hours) or the Emergency Animal Disease hotline on 1800 675 888 (after hours).