[Jacob-list] Fwd: PRO/AH> Selenium poisoning, sheep - USA (ID)

[Katherine Wisor]

Begin forwarded message:

> From: ProMED-mail <promed at promed.isid.harvard.edu>
> Date: Sun Jun 22, 2003  6:35:51 PM US/Eastern
> To: promed-ahead at promedmail.org
> Subject: PRO/AH> Selenium poisoning, sheep - USA (ID)
> Reply-To: promed at promed.isid.harvard.edu
>
>
> SELENIUM POISONING, SHEEP- USA (ID)
> ***********************************
> A ProMED-mail post
> <http://www.promedmail.org>
> ProMED-mail, a program of the
> International Society for Infectious Diseases
> <http://www.isid.org>
>
> Date: 21 Jun 2003
> From: Dee Hadorn <bluemohair at earthlink.net>
> Source: the Casper Star Tribune newspaper
> <http://www.trib.com/AP/wire_detail.php?wire_num=10041>
>
>
> Hundreds of sheep die after eating toxic plants
> -----------------------------------------------
> SODA SPRINGS, Idaho: More than 300 sheep grazing near a former 
> phosphate
> mine died last month after eating plants contaminated with selenium, a
> waste product from mining. The sheep were part of a 2 year study 
> sponsored
> by the University of Idaho and the JR Simplot Company to determine how
> animals react to selenium in the environment. They were grazing by the
> now-defunct Conda phosphate mine, which is owned by Simplot.
>
> Scientists blamed a plant called curlycap gumweed (_Grindelia_), which
> absorbs high levels of selenium from the soil. Selenium is a naturally
> occurring element that is toxic in high levels. Greg Moller, 
> University of
> Idaho associate professor of environmental toxicology, said 
> researchers did
> not anticipate the deaths.
>
> Last summer, the research team gave 72 sheep varying levels of 
> selenium in
> vegetation and water, and only one elderly sheep died, Moller said. 
> They
> [have] allowed the 1400 animal band to graze in the mining area 
> [since] 19
> May this year. By 25 May, the sheep began to die.
>
> Preliminary tests show the curlycap gumweed plants had selenium levels
> about 40 times the recommended maximum. Simplot spokesman Rick Phillips
> said researchers did not include the plant in their earlier tests.
>
> The Conda mine was opened in 1906. Simplot bought the mine in the 
> 1960s and
> closed it in the 1970s. Because mining guidelines were less stringent 
> in
> the past, Phillips said, the contaminated soil is probably near the
> surface. Phillips said the research was a breakthrough. "It's shocking 
> to
> see so many sheep die, but we're learning so much more than we did 
> before,"
> Phillips said. The sheep owners will be reimbursed. In 2001, more than 
> 150
> sheep died from selenium poisoning in the Conda mine area. In 1996, 
> horses
> in the region died from selenium poisoning.
>
> --
> ProMED-mail
> <promed at promedmail.org>
>
>
> [Selenium (Se) toxicity is a serious threat to livestock in the western
> United States. Selenosis may affect all livestock, but especially 
> cattle
> and sheep. Several plant species, generally in the western US, are 
> selenium
> accumulators, such as _Astragalus_ (loco weeds and milk vetches),
> _Onopisis_ (goldenweed) and _Zylorhiza_ (woody asters).
>
> Acute poisoning is caused most often by the single consumption of a
> sufficient quantity of a highly seleniferous plants, which produce 
> severe
> symptoms. Death usually occurs within a few hours. Cattle and sheep 
> are the
> most likely species to be affected, but horses, goats, and swine can 
> also
> be affected. Studies have shown the minimum lethal dose for cattle may 
> be
> as little as 3 mg/kg body weight, while for horses the dose may be 3.3
> mg/kg of body weight, and for swine 1.2 mg/kg of body weight has caused
> death in 5 days. Signs of acute intoxication are abnormal movement, 
> dark
> watery diarrhea, elevated temperature, weak and rapid pulse, labored
> respiration, bloating and abdominal pain, mucous membranes are pale and
> blue, and pupils are dilated. There is no known treatment to reverse 
> the
> effects of the poisoning, and often the animal dies before a diagnosis 
> can
> be made.
>
> Chronic selenosis occurs when there is a prolonged consumption of a low
> level of selenium. "Blind staggers" occurs when animals ingest
> water-soluble selenium compounds naturally found in accumulator plants.
> Toxicity from eating plants or grain with protein-bound, insoluble 
> selenium
> is called "alkali disease."
>
> The signs of blind staggers occur in 3 stages:
> --wandering, stumbling over objects, anorexia, visual impairment;
> --increase in the severity of the first stage, front legs seem unable 
> to
> support the animal;
> --blindness, paralysis of tongue and swallowing mechanism, rapid and
> labored respiration, salivation, and low temperature.
>
> The animal will die within a few hours of the onset of the third 
> stage. The
> action of the toxicity has been documented to have a delay between 
> stages.
> The first and second stages may go unnoticed. Weeks later, the animal 
> may
> show signs of the third stage and die. In sheep, it is more difficult 
> to
> diagnose because the stages are not as well defined as in cattle.
>
> Toxic amounts of Se can also cause birth defects in offspring from 
> dams fed
> such levels. Alkali disease is more chronic than blind staggers, taking
> longer to be manifest, even perhaps years in some cases. It is caused 
> by
> the animals feeding on plants and grain having protein-bound, insoluble
> selenium. This disease can affect all livestock, but it is detected 
> mostly
> in cattle and horses. Generally signs are lack of vitality, anemia,
> emaciation, stiffness of joints, lameness, rough coat, loss of long 
> hair,
> and hoof sloughing and deformities. Hoof deformities are a classic 
> sign of
> selenium and can cause lameness and severe pain for the animal; food 
> and
> water must be provided to the animal, for it may be hesitant to walk.
>
> Removing the animals from the seleniferous areas is the most effective
> means of preventing the disease. Treating the soil with sulfates (S), 
> to
> change the S:Se ratio, can sometimes depress Se uptake by accumulator
> plants. Studies have shown feeding a higher protein diet may reduce the
> toxicity of Se; animals fed the same amount of toxic selenium but fed a
> higher protein diet lived for a few more days than those animals fed a 
> low
> protein diet. Dilution of high Se feeds with low Se feeds in a mixed 
> ration
> will help to prevent toxicity. Recognition of seleniferous plants, 
> proper
> land management, and grazing control are all necessary to completely
> prevent selenosis. - Mod.TG]
>
> .......................tg/sh
>
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