Watch Livestock for Blue-Green Algae Poisoning

 BROOKINGS, S.D. -- Drinking from stagnant ponds after hot, dry weather can prove lethal to animals if they ingest large quantities of blue-green algae.
 
South Dakota State University Extension Veterinarian Bill Epperson said there are a number of different species of blue-green algae, or cyanobacteria. Some form toxins that affect the nervous system. Others form toxins that mainly affect the liver.

 SDSU Extension Extra 11007, "Blue-Green Algae Poisoning" can be found at http://ars.sdstate.edu/extbeef/Drought_Management.htm in pdf format.  Other information on drought is available at http://sdces.sdstate.edu/drought/.

Epperson said animals may die suddenly - within minutes - of ingestion of blue-green algae often concentrated as a scum on the downwind side of ponds.  Animals may also be affected hours or days after ingesting the organisms.  Rain or any disturbance of the water tends to break up the scum and make poisoning less likely.

Blue-green cells may have the appearance of scum, "skin" or "paint" on or just under the water surface.  Blue-green algae colonies may be visible to the naked eye as very fine grains of green sand or green blobs on the water surface.  Other species of blue-green algae may look like tiny grass clippings, and still others cannot be identified without a microscope.  When picked up, blue-green algae disperses in the water, and does not hang together in a stringy mass.

Signs of Blue-Green Algae Poisoning:

Most all animals, including cattle, sheep, horses, pigs, dogs, ducks, fish, and wild animals can be affected. Livestock affected with the nervous system toxins may show signs including muscle tremors, decreased movement, difficult breathing, collapse, and convulsions.  However, many cases show no signs except sudden collapse and death.  Animals affected with blue-green species that produce liver toxins may show signs of weakness, pale colored mucous membranes, mental derangement, bloody diarrhea, and ultimately death.

Animals that survive poisoning may lose weight and become chronic poor-doers.  A very few may develop photosensitization ­ sunburn that affects lighter areas of skin including the muzzle, udder/teats, vulva/anus, and white colored hide areas of the back and sides.  Producers usually first notice the skin of these areas sticking up, drying out, turning black, then peeling off, leaving fresh new skin underneath.

Diagnosis:

 Blue-green algae poisoning may be suspected based on history, and finding blue-green staining on the hair coat.  A veterinarian should necropsy dead animals to rule out other causes of death.  A complete set of tissue samples, including liver, brain, and stomach contents, from a recently dead animal can assist making a diagnosis.

A water sample from the suspected area may be obtained and examined to determine the presence of blue-green algae species.  Water samples should be taken from an area with large amounts of algae.

"It must be taken as soon as possible after discovery of deaths, since winds may shift and disperse the algae," Epperson said.

One gallon of water should be collected and frozen, and a small amount (five milliliters) taken and refrigerated and another small amount taken and diluted 50:50 with 10 percent formalin. These samples can be sent to the South Dakota Animal Disease Research and Diagnostic Laboratory for examination.

 Treatment of affected animals is infrequently attempted and rarely successful. Treatments aimed at evacuating gut contents, or binding toxins, such as activated charcoal, may help in mild exposures. If a neurotoxin producing blue-green algae is suspected, atropine may be helpful, depending on the species affected.

Prevention and Control:

Blue-green algae poisoning is unpredictable and sporadic.  Poisoning is more likely in stagnant natural waters following hot dry weather.  Producers should monitor and watch for algae blooms during times of hot weather.

Downwind drinking areas may be fenced off for animals to drink from areas where the concentration of blue-green organisms is unlikely.  Water can be pumped from several yards below the surface of a fenced off pond to a nearby tank for livestock.  Other water sources may be an alternative for some producers following times of high temperature.

Sites with a history of repeated blue-green algae blooms can add copper sulfate to the water as an algaecide.  The recommended maximum concentration in the water is one parts per million.  This is equivalent to 2.7 pounds/acre-foot or eight pounds per million gallons of water.  The copper sulfate must be applied evenly over the water surface, and is best applied before large concentrations of blue-green algae are present.  One treatment is usually good for two to three weeks.

For more information, contact any county Extension office or veterinarian.
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Contact: Bill Epperson, (605) 688-6589
** For links to other sites showcasing SDSU's work in teaching, research, and Extension, visit http://sdces.sdstate.edu.

Wendy Mohrhauser, Intern
AgBio Communications Unit
South Dakota State University
ACC, Box 2231, Rm 200
Brookings, SD 57007
Telephone: (605) 688-5795