Algae linked in cattle deaths
Blue-green algae has been identified as the probable cause of death in 22 cattle at a Marion County area ranch in late May, a shocking reminder that the problem of cyanobacteria is as real for private farm ponds as it is for Marion Reservoir and Marion County Lake.
Deon van der Merwe, head of the toxicology section at the Veterinary Diagnostic Laboratory at Kansas State University, said blue-green algae in farm ponds is a growing concern.
“This has been something, especially last summer, that has had a huge increase in the number of samples we get that are toxic for blue-green algae,” van der Merwe said. “It seems it is a much wider increase than just this area.”
Veterinarian Brendan Kraus of Spur Ridge Animal Hospital in Marion investigated the cattle deaths. At the request of the rancher he declined to provide a name or the exact location of the mass die-off, but did provide details about the incident.
“They were apparently healthy two days prior to the owner finding them,” Kraus said. “The dead cattle represented 30 percent of the pasture. They were shipped in for custom grazing from another state. They looked like they simply fell over dead where they stood.”
The dead cattle were already decomposed to the point post mortem examinations were useless, Kraus said. Kraus and the rancher were left searching for clues in the surrounding area for the cause of death.
“We went immediately to the water sources,” Kraus said. “The third pond had some algae in it that we suspected was blue-green algae. The algae itself is usually kind of a turquoise color, and sometimes it will concentrate on the downwind side of the pond. That was kind of the case here. This was a shallow area where footprints indicated the cattle had been drinking.”
Kraus drew samples of the pond water and sent them to the KSU toxicology lab for analysis.
“The water sample we got contained examples of two species we don’t expect to see this early in the season,” van der Merwe said. “Both of these species have potential for producing high levels of toxins, but they don’t always do that. It appears in this case they did.”
“The type that was in highest numbers is capable of creating neurotoxins that can shut down the nervous system. This type of toxin is capable of killing animals in mere minutes,” Kraus said.
Van der Merwe said the early onset of warm weather is a possible explanation for the appearance of these strains, and said nutrient runoff from is a contributing factor to cyanobacteria growth.
“This particular pond we believe was affected due to the trees surrounding the south side which blocked the wind, but also that some of the feed commodities stored near it produced runoff that was high in nitrogen and phosphorus, which algae love,” Kraus said.
This is the first case of cattle deaths Kraus has encountered where blue-green algae has been strongly been implicated, but he didn’t rule out the possibility past isolated cattle deaths might have had the same cause.
“I think we’ve had some suspicions in the past, but testing of a single animal is just too difficult,” Kraus said.
Kraus noted that the evidence pointing to blue-green algae is strong but circumstantial.
“There’s no way to definitively prove that was the cause,” Kraus said.
Humans exposed to cyanobacteria toxins exhibit reactions ranging from irritating skin rashes to respiratory complications to severe vomiting and diahrrea. Van der Merwe explained the difference that leads to animal deaths.
“What places animals at risk is that they often ingest large quantities because that is their only water source,” van der Merwe said.
“Humans are as susceptible as other species are. People don’t usually drink pond water. That toxin is a liver poison and it will actually destroy the liver irrespective if it is a person, a cow, or a dog. If the dose is small it will not proceed to that,” van der Merwe said.
Color changes in pond water are a cue farmers may want to have it tested, van der Merwe said.
“Usually the color will change from background brownish to more of a green. Sometimes it looks like little flecks of green near the surface or on the surface,” van der Merwe said.
“All ponds have algae and moss,” Kraus said. “This looks enough different it catches your attention if you’re looking. I think it would be good to look at the water once a week or every few days.”
Directions and specifications for submitting pond water samples for blue-green algae testing are available on the Veterinary Diagnostic Laboratory website at http://www.vet.k-state.edu/depts/dmp/service/index.htm. The price for the test is $18.50, and is scheduled to increase to $19 on July 1. Results are available within a business day of receipt of the sample.