Volume 25, Number 6—June 2019
Research
Mass Die-Off of Saiga Antelopes, Kazakhstan, 2015
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Sasan Fereidouni, Graham L. Freimanis, Mukhit Orynbayev, Paolo Ribeca, John Flannery, Donald P. King, Steffen Zuther, Martin Beer, Dirk Höper, Aidyn Kydyrmanov, Kobey Karamendin, and Richard Kock
Abstract
In 2015, a mass die-off of ≈200,000 saiga antelope in central Kazakhstan was caused by hemorrhagic septicemia attributable to the bacterium Pasteurella multocida serotype B. Previous analyses have indicated that environmental triggers associated with weather conditions, specifically air moisture and temperature in the region of the saiga antelope calving during the 10-day period running up to the event, were critical to the proliferation of latent bacteria and were comparable to conditions accompanying historically similar die-offs in the same areas. We investigated whether additional viral or bacterial pathogens could be detected in samples from affected animals using 3 different high-throughput sequencing approaches. We did not identify pathogens associated with commensal bacterial opportunisms in blood, kidney, or lung samples and thus concluded that P. multocidaserotype B was the primary cause of the disease.
The saiga antelope (Saiga tatarica tatarica and S.t. mongolica) is a critically endangered species (1) with populations located in Kazakhstan in addition to small remnants in Russia and Uzbekistan and a subspecies in Mongolia. Each year during the month of May, Saiga antelopes gather in Kazakhstan for calving. Mass die-offs in their populations have been reported previously and were attributed to viral and bacterial etiologies, including pasteurellosis (2). However, the diagnosis in most of these events has been unreliable because of insufficient fresh sampling and diagnostic work (2).
During a large outbreak in 2015, extensive diagnostics and environmental studies were undertaken, subject to restricting factors such as remoteness and limited cold chain resources. Annual disease monitoring in saiga antelopes had been established after die-offs occurred in western Kazakhstan in 2010, and an international multidisciplinary research team was on the ground at the time of the die-off, performing routine surveillance (3,4).
The mass die-off of saiga antelopes in Kazakhstan started around May 10, 2015, and caused ≈200,000 deaths across several calving groups within 3 weeks. These subgroups of saiga antelopes were spread discretely across a landscape of several hundreds of thousands of square kilometers. The number of dead animals constituted more than two thirds of the global population of saiga antelope at the time. The outbreak wiped out 88% of the Betpak-Dala population in central Kazakhstan (5) and appeared to have a 100% case-fatality rate.
Laboratory results on the microbiologic, pathologic, and environmental conditions at the time of the 2015 outbreak suggested hemorrhagic septicemia caused by Pasteurella multocida serotype B and triggered by environmental conditions (3,6). However, whether a second unknown infectious agent had predisposed the animals to infection with P. multocida was unclear from the laboratory results. Given the opportunistic nature of Pasteurella, the objective of our study was to attempt to identify whether any additional unknown potential causative pathogens were present in samples (taken from 10 animals) that might may have contributed to the die-off.
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