“They were apparently healthy two days prior to the owner finding them,” Kraus said. “Upon my visit, there were no sick ones in the group.”
He said the dead cattle were too decomposed to conduct a postmortem exam. The animals were discovered scattered around and sometimes in a group.
“They looked like they simply fell over dead where they stood,” Kraus said. He and the owner went immediately to the water sources.
“The first two ponds appeared normal. The third pond had some algae in it that we suspected was blue-green algae.”
The pair then walked to the side of the pond where wind had blown the algae into a concentrated location.
“This was a shallow area where footprints indicated the cattle had been drinking,” Kraus said. “This area of the pond had a distinctly different color and one could see where the algae had settled into the small depressions of previous footprints.”
A sample of the water was sent to a diagnostic laboratory, which confirmed the presence of two types of toxic algae.
“I can tell you that one type of algae is capable of producting a toxin that can cause damage to the liver and can cause death due to liver failure,” Kraus said.
“The other type of algae may produce a neurotoxin that can inhibit the nervous system and potentially lead to respiratory arrest, which I believe is probably what happened in this case.”
Kraus said he is not sure whether the strains of blue-algae found at pond is the same as the strains that have bloomed in Marion Reservoir and Marion County Lake.
“As a general term, the family of blue-green algae has several species,” he said. “Different types are capable of producing different toxins, but just because the algae is growing doesn’t mean they are also producing toxins.”
Kraus said this is the first case he has seen that has produced this kind of cattle kill.
“It’s not the first time we’ve seen blue-green algae (in a cattle pond), and it’s not the first time we’ve been suspicious,” he said. “But I haven’t seen one quite so encompassing or damaging.”
Kraus said the landowner, who asked that his identity and the location of the pasture not be identified, has occasionally tested the water in the ponds.
“This water traditionally had a higher phosphorous concentration than the other ponds, which is something blue-green algae like,” Kraus said.
The veterinarian said he’s not aware of any practical thing cattle ranchers can do that is practical to prevent an incident of toxin poisoning.
“Algae are tough because we can’t really control or predict why it would grow in one body of water and not in another under the same conditions,” Kraus said.
“It might not hurt to be checking ponds regularly during the summer. If a color change is noticed, or concentrations of algae that look different than normal are found, then have that water tested. Blue-green algae has a little different look to it. It does look more turquoise than basic pond algae.”
Kraus emphasized that the death of the cattle has not been absolutely confirmed as caused by blue-green algae toxin because the dead animals were too decomposed to retrieve viable tissue or stomach contents to sample for testing.
“We are highly suspicious, but there was no way to get tissue samples on these animals just because of the heat,” he said. “We basically looked at the situation and the presence of the algae, and that was the best we could do.”