Several African elephants have died in the past few years.
African Elephant Deaths
Back in August 2020, Chris Foggin, a wildlife veterinarian, was wearing a mask and dissecting an elephant that was thought to have passed away from anthrax. As he was doing so, he received a call that more fatalities had been reported.
The day after, five other African elephants were found dead under the hot sun of Zimbabwe. While Foggin was aware that his team was unable to reach all the carcasses to gather post-mortem tissue samples, he gathered what he was able to before the decomposition of the carcasses.
In November, 35 African elephants, or Loxodonta africana, passed away in northwestern Zimbabwe. This was just over the border from Botswana, where over 350 elephants reportedly died just months before.
The rising deaths of these elephants led to growing concerns. Starvation, anthrax, and poaching were all considered possible causes. In September of that year, Botswana's government attributed the deaths to an unspecified cyanobacterial toxin that could have contaminated watering holes.
After three years, another culprit emerged for Zimbabwe's mysterious 35 elephant deaths.
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Why Did These Elephants Die?
These 35 elephants may have died because of a Pasteurella bacteria that resembles a specific strain known as Bisgaard taxon 45. This strain has been connected to other infections in wildlife. However, it was not known to kill African elephants.
Foggin looked into the tissue samples in his lab and noted that several of the creatures' organs had ruptured blood vessels. This made him suspect that it was a case of blood poisoning or hemorrhagic septicemia.
Most samples of blood were also found to contain colonies of bacteria. Moreover, spleen, liver, and blood tissue samples from one specific elephant were found to host heavy Pasteurella bacteria grown that suspiciously looked like Bisgaard taxon 45.
Six out of 15 elephant samples appeared to contain biochemical or genetic evidence of Bisgaard taxon 45. No toxins, poisons, or viral infections were picked up.
Foggins notes in the study "Pasteurella sp. associated with fatal septicemia in six African elephants" that documents the findings that bacterial septicemia is now part of a growing list of illness-related threats to the conservation of elephants.
The transmission route and infection source remain a mystery for all outbreak investigations. Elephants are remarkably social creatures. At least 11 are due within 24 hours in roughly 50 square kilometers.
Consecutive rainy seasons came before the outbreak. By the time the mass deaths occurred, the area was in the grips of drought. Hence, the researchers suggest that one possibility is that the drought and heat conditions could have triggered the bacteria to become infectious or transmissible among elephants.
However, several unanswered questions remain regarding the 2020 mortality event in Zimbabwe and the Bisgaard taxon 45. In a blog post, Laura Rosen, a veterinary epidemiologist and co-author of the study, writes that they do know how the bacteria.
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