VICTORIA FALLS, ZIMBABWE — In late August 2020, wildlife veterinarian Chris Foggin was in the midst of investigating the mysterious deaths of several elephants suspected of anthrax poisoning when he received a call about more fatalities. The next day, another five dead elephants were discovered in the scorching Zimbabwean sun. Foggin and his team worked quickly to collect post-mortem tissue samples before the carcasses decomposed, knowing they wouldn’t be able to reach all of the dead elephants.
By November, a total of 35 African elephants had perished in north-west Zimbabwe, sparking concerns as poaching, starvation, and anthrax were all ruled out. According to the Botswana government, more than 350 elephants had died in Botswana months earlier from an unspecified cyanobacterial toxin. It wasn’t until three years later, that a new culprit emerged for the 35 mysterious elephant deaths in Zimbabwe: a Pasteurella bacterium resembling a strain called Bisgaard taxon 45, which is not known to kill African elephants.
The investigation led by Foggin revealed that the deceased elephants had ruptured blood vessels and suffered from hemorrhagic septicaemia, or blood poisoning, leading to the suspicion that the Pasteurella bacteria was the cause of death. The outbreak event was preceded by back-to-back poor rainy seasons, and the researchers suggested that the heat and drought conditions might have somehow triggered the bacteria to become infectious or spread between elephants. Though the source of infection and route of transmission remained unknown, the Victoria Falls Wildlife Trust is now equipped to test for Pasteurella Bisgaard taxon 45 and plans to keep looking for the bacterium in elephants and large carnivores.
The study on the elephant deaths was published in Nature Communications and provides critical information for wildlife veterinarians and conservationists to consider going forward. Despite the progress made in understanding the cause of the deaths, there are still many unanswered questions about Bisgaard taxon 45 and the 2020 Zimbabwe mortality event.