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Deaths of 60,000 saiga antelopes still confounds scientists

By Karen Graham     Sep 4, 2015 in Environment
In May, 2015, a mysterious illness killed off half of the world's saiga antelopes, a critically endangered species that roam the steppes of central Kazakhstan.
Digital Journal ran the story of the initial die-off in late May. Soon after, geoecologoist Steffen Zuther and his colleagues arrived in Kazakhstan to observe the birthing process of the saiga antelopes.
But while they were there, they started seeing dead antelopes. In four days, 60,000 saiga antelopes lay dead across the steppes. As conservationists and veterinarians tried to stem the tide of deaths, they heard of similar die-offs in other herds across the country. Discovery News says that by early June, the mass deaths had finally stopped.
The mystery illness, which started on May 10, causes severe diarrhea and breathing difficulties and has a 100 percent mortality rate. At that time, a team of veterinarians and scientists, led by Richard Kock of the Royal Veterinary College in Hatfield, UK was called in to investigate.
Researchers find clues to the mass die-off
Clues have been uncovered that point to the reasons behind the unexpected loss of more than half of the country's 257,000 saiga antelopes. Bacteria played a role in the demise of the antelopes. but exactly how the harmless bacteria could take such a frightening toll is still unknown.
Zuther is quoted by as saying, “The extent of this die-off, and the speed it had, by spreading throughout the whole calving herd and killing all the animals, this has not been observed for any other species. It’s really unheard of.”
Saigas play an important role in the ecosystem of the arid grassland steppes. The Eurasian steppe runs from Moldavia, across Ukraine and Siberia, and into Hungary. It is on these steppes that the saiga feeds on plant materials that can't decompose in the region's harsh winters.
By doing so, the antelope also helps in preventing wildfires. The antelopes help in breaking down organic matter, as well as recycling nutrients. They also provide meals for predators. "Where you find saiga, we recognize also that the other species are much more abundant," Zuther told Live Science.
The herds usually congregate with other herds during the winter, and when they migrate during the fall and spring. Then the herds split up to calve their young in the late spring and early summer months. The die-off started during the calving period.
Until now, researchers could only speculate as to the cause of the mass die-offs. They thought the abundance of greenery could have something to do with the deaths, possibly leading to digestive problems that in turn, led to bacterial overgrowth in the animals' guts.
Doing a detailed analysis
This time, researchers took detailed samples of the saiga's environment, from rocks and soil the animals walked on to the plants they ate and water they drank. Samples were also taken of the ticks and other insects that feed on the antelopes.
The team was able to do necropsies on animals immediately after they died, all the while keeping detailed notes on the deaths of many of the animals as they died. Zuther says the females cluster together to give birth, and it is the mothers that are hit the hardest. After giving birth, the mothers died first, followed by the calves which were too young to eat vegetation.
It was thought that based on the sequence of events, the die-offs had something to do with a bacteria being transmitted through the mother's milk. Tissue sample studies found that toxins produced by Pasteurella and possibly Clostridium bacteria caused extensive bleeding into the internal organs. Interestingly, Pasteurella is normally found in ruminants, such as the saiga, and usually don't cause problems, unless the animal has a weakened immune system.
But genetic analysis of the bacteria has found only normal, garden-variety disease-causing types, says Zuther. "There is nothing so special about it. The question is why it developed so rapidly and spread to all the animals," he said.
Zuther says that the only environmental cause for the mass die-off could be the unusually hard winter this past year, and the overly wet spring that resulted in an abundance of lush vegetation and standing water. He says this could have helped to spread the bacteria more easily, even though he doesn't think that is so unusual. He and his colleagues plan to continue their research into this unusually big mass die-off.
More about saiga antelope die off, 60k in four days, bacteria plays a role, Kazakhstan, Gut bacteria
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