New Mexico Department of Game & Fish wildlife specialist Kerry Mower hit the nail on the head in early Sept. after investigating the mysterious death of about 100 elk on a northeast New Mexico ranch. Toxicologists have determined Anabaena, a type of blue-green algae that can produce a deadly but short-lived neurotoxin, was the silent culprit responsible for the incident.
"We are probably looking for some type of environmental condition of unknown type or variety," Mower said Sept. 4 after spending days on the ranch searching for clues.
The neurotoxin, anatoxin-a, was found in a water sample taken from a fiberglass livestock tank not far from where the elk were found spread across a small meadow in a remote area of the ranch.
Investigators say water samples taken from three fiberglass tanks in the area shortly after the kill off all tested positive for trace amounts of the neurotoxin and are now considered to be the cause of death.
Earthen water tanks in the area were also tested but no traces of neurotoxin could be found in those samples.
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Investigators say elk have a habit of movement, finding water and then resting. Mower believes that may have been what happened on the day of the kill off. Moving through a natural corridor on the land where the tanks are located, the herd probably stopped at one or more of the tanks for water and proceeded to a resting area where they collapsed. Investigators noted signs of physical struggle on the ground where the animals were found.
Mower said investigators considered several suspected causes of death after the initial investigation was complete.
"We looked at such things as EHD (Epizootic Hemorrhagic Disease), which is not uncommon. We also looked at the possibility of pathogens such as anthrax, natural causes such as lightning, and chemical toxins from nearby industrial applications," Mower explained. In spite of helicopter flyovers of the area, no other animals were found.
Early tests were inconclusive
Officials say early water tests indicated a normal presence of bacteria in samples collected from the area but not at levels considered toxic. Mower said more comprehensive tests were needed before any conclusions could be made final. He said only testing by a specialized laboratory could have found the trace amounts in the samples.
"Toxicology examinations were performed at an out of state lab and these types of tests require time. But it appears we have found the definitive cause," Mower explained.
While investigators mull over the results, they will be looking at why the neurotoxin was discovered in the fiberglass tanks and not the earthen tanks, a possible clue to the elk deaths. But Mower warns the type of tanks may not have had anything to do with the development of the algae blooms and neurotoxins.
Blue - green alga is a microscopic cyanobacteria that can grow in warm, stagnant water in ponds, lakes and water tanks. Not all types of algae produce toxins that are harmful to humans and animals. But it is not the first time neurotoxins have been blamed for large animal kill offs. Anatoxin-a was at fault in the early 1960s when a large herd of cattle in Canada died. Toxicologists say it doesn't take a great deal of toxin to be deadly to thirsty animals.
Mower says temperatures leading up to the elk kill in New Mexico were warm, but not excessively hot. But with enough sunshine and the right conditions, blue-green algae can form, and toxins are often the result.
The New Mexico Department of Health warns that toxins from algae blooms can also be toxic to humans. While no cases of human death from algae toxins have been reported in New Mexico, health officials say people have fallen sick from swimming or wading through algae blooms.
Contact with blooms can cause rashes or skin irritations and swallowing infected water can cause diarrhea, vomiting and neurotoxic symptoms, possibly leading to serious illness or death.
With hunting season underway in New Mexico, wildlife officials say so far no other reports of unexplained animal deaths have been reported. But game and fish officials warn hunters not to harvest animals that exhibit unusual behavior or appear sick, and when discovering a sick or dead animal they should report the incident to the department’s toll-free information line, 888-248-6866.