Blue-green algae bloom kills 32 cattle in S. Oregon

A blue-green algae bloom in a Lake County, Ore., pond killed 32 cattle. Though not all blooms are toxic, ranchers and others should report any outbreaks so they can be tested.

A blue-green algae outbreak in a Lake County, Ore., reservoir has killed 32 head of cattle.

The outbreak began on KV Bar Ranch about June 12. John Shine, owner of the south-central Oregon ranch, said the steers “just started dying.” That afternoon 11 died, and the rest followed within 72 hours. Although Shine is the ranch owner, the cattle lost belonged to another rancher.

“We had a reservoir that cattle have been drinking out of for 60 years, and never had a problem. Then this breeze comes from the north and carried this layer of scum 3 to 4 feet from the edge and that’s what they were drinking. We noticed the cattle had blue legs,” Shine said. “We thought it was poison at first. We didn’t know what it was.”

The color and the smell were the most noticeable things to Shine.

“It’s a turquoise color; it’s not green,” he said. “It smelled like rotten seaweed at the ocean.”

Despite its name, blue-green algae are actually bacteria. It occurs naturally in many fresh and still waters, and is recognizable by a collection of surface scum that “looks like a green paint spill,” said Dr. Rod Ferry, veterinarian at Lakeview Animal Hospital. Although some blue-green algae species are harmless, others produce a toxin that in large doses can affect the liver or the nervous system. The toxin can affect both animals and people.

“It’s unusual to lose 32 (cattle) in one hit,” said Theo Dreher, a microbiology professor at Oregon State University. “It’s probably not infrequent in cases of ranch land cattle where a few stock die, but this is pretty exceptional, and points out the danger that does exist when you get one of these blooms.”

They suspect that the bloom formed because of Oregon’s increased rainwater this winter and spring, after several years of drought. During that time excess manure may have washed into tanks, ponds or reservoirs, which caused an increased nutrient load for the algae to feed on and grow, creating the bloom, Pete Schreder, OSU Extension livestock agent, said in an email.

Wind can also help aggregate the clumps of algae.

For producers, losing 32 head “is relatively devastating,” Schreder said.

After they eat the toxin, cattle will quit eating, stagger or be unable to rise from lying on the ground. Eventually, they will go into a coma and die. Death can come up to 72 hours after initial exposure.

“There is no treatment available. It’s pretty impractical to treat cattle with a lethal dose because it just can’t save them,” Ferry said.

Ranchers should be diligent and check all water sources for anything atypical. If they see anything suspicious, keep livestock away from the water and call the local OSU Extension office.

This is the first reported case of blue-green algae in Lake County, Schreder and Ferry said.

“I’ve been here for 30 years and haven’t seen it in this county to this degree,” Ferry said. “It’s not something experienced here.”

There have been other sightings of blue-green algae in Oregon, according to Dreher, the microbiology professor. Toxic species have been found in the South Umpqua River, Detroit Lake, Upper Klamath Lake, South Tensile Lake and areas of Lake Billy Chinook, according the Oregon Health Authority’s algae bloom advisories website.

While some algaecides are available to treat smaller ponds, they are temporary and costly. Any chemical treatments will affect too many other natural systems in the water, and would not be feasible, Schreder and Dreher said.

“We really just have to let it run its course. It grows and blooms, and then dissipates over time,” Schreder said.

Dreher estimated that the dissipation period can last a couple of weeks.

“In a small reservoir many things can happen. The bacteria can die off and be eaten by other organisms and bacteria, or it could settle out on the sediment under the water and stop growing or it can be disrupted by currents and wind until the concentration lowers,” Dreher said.

Dreher also reminds producers to be aware of the algae if they’re irrigating their pastures, as that might cause further exposure problems.

Once a bloom has been formed, reservoirs or ponds can be more susceptible in the future.

“All water has the capability, but it happens when the stars align just right,” Schreder said. “We’re looking into the summer and can’t predict if we’re going to have more blooms; we just have to watch and see. We want to alert people to be diligent and keep an eye out on ponds and reservoirs this year.”

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