An international team of scientists has unraveled the mystery behind the sudden deaths of 200,000 antelopes in Kazakhstan in May 2015.
The strange mass mortality event, which lasted three weeks, left saiga antelope carcasses strewn across a vast area the size of the British Isles. Classified as critically endangered, the incident wiped out 80 percent of the global saiga antelope population.
Experts have long been puzzled by the animals’ deaths, which were the result of haemorrhagic septicemia, caused by the bacteria Pasteurella multocida. The pathogen, however, was likely living harmlessly in the saigas’ tonsils up until the event, according to the Royal Veterinary College in London, which participated in the research, prompting scientists to seek answers about what triggered the mass deaths.
The international research team found that a number of factors contributed to the strange phenomenon. Specifically, increased humidity and raised air temperatures in the days before the deaths appear to have triggered an “opportunistic bacterial invasion” of the blood stream, causing septicemia, or blood poisoning, according to a statement.
In addition to the 2015 event, the scientists studied two saiga mass mortalities in the 1980s and identified clear climate patterns. “The probability of sudden die-offs increases when the weather is humid and warm, as was the case in 2015,” they explained, in the statement.
In 1981 70,000 saigas died in a mass mortality event, although this number was dwarfed by the 270,000 that died in a 1988 die-off, The Verge reports.
The deaths also tend to occur during calving. The animal bears the the largest calves of any ungulate species, experts note. “This allows the calves to develop quickly and follow their mothers on their migrations, but also means that females are physiologically stressed during calving,” they said.
Richard Kock, professor in emerging diseases and lead researcher at the Royal Veterinary College, noted that recent die-offs in saiga populations have shed new light on the strange events. “The 2015 Mass Mortality Event provided the first opportunity for in-depth study, and a multidisciplinary approach has enabled great advances to be made,” he said, in the statement. “The use of data from vets, biologists, botanists, ecologists and laboratory scientists is helping improve our understanding of the risk factors leading to MMEs – which was beneficial when another MME occurred, this time in Mongolia in 2017.”
Last year, a saiga sub-species in Mongolia was also hit, with about 6,000 dying from a virus that spilled over from livestock. The deaths accounted for about 60 percent of the saiga sub-species population in that area.
The saiga antelope has also been subject to high levels of poaching since the 1990s, as well as encroachment on its habitat from the likes of railways, roads and fences.
“Improved knowledge of disease in saigas, in the context of climate change, livestock interactions and landscape changes, is vital to planning conservation measures for the species’ long-term survival,” added Kock.
The scientists’ research is published in the journal Science Advances.
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