It could have been a scene right out of a horror movie: 100 dead elk strewn across a three-quarter-mile stretch of New Mexico riverbank, appendages contorted in a ghastly frieze of agony. All of them had perished violently within the same 24-hour period, and when state biologists arrived on the scene on August 27, nothing could be ruled out. Anthrax, hemorrhagic diseases, poaching, and malicious poisoning were just a few of the frightening possibilities.
The real answer turned out to be less obvious. After collecting tissue samples from the dead animals and water samples from the nearby stream, New Mexico’s Department of Fish and Game sent the physical evidence to a number of biolabs around the country. The elk samples came back negative for the usual zooinotic (animal-based) illnesses, but one curious result came back from the water: it was teeming with traces of anabaena, a naturally occurring type of cyanobacteria.
Anabaena, which manifests in large quantities as blue-green algae, is a known killer. It produces a deadly neurotoxin called anatoxin-a (nicknamed “Very Fast Death Factor”) which, when ingested, can cause lethargy, confusion, memory impairment, respiratory convulsions, and paralysis. Anatoxin-a can kill a mouse in under five minutes and a cow in just a few hours. Indeed, the poison has been implicated in mass livestock die-offs before, notably Wyoming in 2004 and California in 2006.
Given New Mexico’s physical conditions, this lead made perfect sense to biologists. In the late summer, when the weather is hot and ponds are stagnant, algae can bloom at an astounding rate, contaminating the entire surrounding water supply. But the neurotoxin itself is extremely unstable; anatoxin-a begins to break down within minutes of being introduced to sunlight. Thus, the danger is fleeting—the fatal conditions that killed the elk probably lasted less than 36 hours. The Fish and Game Department was satisfied with its findings; on October 22, it concluded its investigation and declared the case closed as an isolated one-off.
But does this anabaena incident belie a larger public health issue? There are no official guidelines for testing for anatoxin-a at any level, state or federal, because it is such an elusive poison. Most species of blue-green algae are not deadly, and even the 10% that contain anatoxin-a might be fine one day and lethal the next. To date, there have been just two dozen injuries and one confirmed human fatality due to algal blooms, so I’m not going to hype up the danger too much here. Hopefully, most people know to avoid drinking untreated water. Fewer people, however, are probably aware that every so often each summer, their local pond or river might turn into a short-term death trap.
Human risk will likely remain quite low, but I’d wager you’ll hear more about anabaena in the near future. As The Washington Post reported in September, nitrogen and phosphorus run-off from fertilizer usage is increasing blue-green algae’s spread around the country, raising the likelihood of more deadly blossoms. New York, Kansas, and Washington have recorded the most toxic algae incidents so far in 2013, but it remains to be seen if that’s just because those are the only three states really paying attention.
The gruesomeness of the New Mexico elk die-off may have been a fluke, a rare confluence of bacteria and bad luck. But given the uptick in these anatoxin-a wildlife deaths over the past decade, it’s also possible that we’re only just now seeing the beginning of things to come. After all, animals don’t have the luxury of Brita filters.
Trent Knoss is the digital editor at Backpacker Magazine and lives in Boulder, Colorado.