The Mysterious Mass Death of the Saiga


Hope may be on the horizon for the critically endangered saiga, an antelope in Eurasia that can be traced back to the ice age. Saiga populations in Kazakhstan have been showing signs of recovery after a devastating mass die off occurred last year, killing over 200,000 antelope in a span of weeks.
The mysterious illness was first seen in 2010 on a smaller scale, and resembled a previous die off recorded in 1988. In May 2015, conservationists arriving in Kazakhstan to study saiga herds found the animals dying at an alarming rate. Within four days, an entire herd of 60,000 were dead.
Researchers studying the infection observed that nursing females died first, followed by their calves. Tissue samples taken from the antelope implicated the bacteria Pasteurella, and determined the cause of death to be hemorrhagic septicemia. Strangely enough, Pasteurella multocida is a common and typically harmless bacteria found in the respiratory tract and intestines of many different animals.
While the nature of the outbreak is still unknown, climate change may have impacted its virulence. Most incidences of mass death occurred in May, and in 2015 there was an unusually cold winter followed by a very wet spring. Scientists postulate that the surplus of plants led to a build up of bacteria in the saiga’s stomachs, ultimately leading to internal bleeding. The antelope are also particularly vulnerable during the spring, when they shed their winter coats and females give birth and nurse young. During this time, the animals have less resources to devote to immune defenses. Other studies of grazing animals have shown that climate change can weaken immune systems while conversely provoking microbes to make toxins.
The effects of the outbreak are especially worrisome since saiga populations were already reaching extinction from poaching. The horns of the saiga are used in traditional chinese medicine and illegally traded. If driven to extinction, greater impacts on the grassland steppe ecosystem could be seen. Grazing helps recycle nutrients and break down organic matter, as well as control leaf litter that can be a potential wildfire hazard. Saiga are also an important prey source and indicator of biodiverstiy.
Luckily, a significant number of males have survived both poaching and the infectious outbreak, allowing for reproduction. Census data collected this year shows an increase in all three saiga populations in Kazakhstan, nor did the infection reoccur in 2016. However, saigas are still critically endangered and their numbers must be protected against poaching, should an outbreak happen again.



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