What happened and who is to blame?

In late August 2020, wildlife veterinarian Chris Foggin was examining an elephant suspected of dying from anthrax when he received a call saying there were several more deaths. The next day, five more dead elephants were found under the scorching Zimbabwean sun. Foggin knew he and his team couldn’t get to all the dead elephants to collect post-mortem tissue samples, but he collected what he could before the carcasses decomposed.

By November, a total of 35 African elephants (Loxodonta africana) had died in northwestern Zimbabwe, just across the border from neighboring Botswana; More than 350 elephants died here a few months ago.

Concerns have increased over poaching, starvation and the disappearance of anthrax, a naturally fatal bacterial disease. In September 2020, the Botswana government attributed elephant deaths in Botswana to an unspecified cyanobacterial toxin that may have entered waterways.

Three years later, another culprit emerged: a Pasteurella bacterium similar to a strain called Biesgaard taxon 45, which has been associated with other wildlife infections but had not previously killed African elephants.

Examining tissue samples in his laboratory at the Victoria Falls Wildlife Trust, Foggin noticed that many of the dead elephants had ruptures in the blood vessels of their organs, leading him to suspect hemorrhagic septicemia, or blood infection. Many of the blood samples smeared on microscope slides also contained bacterial colonies. Tissue samples taken from the brain, liver and spleen of one particular elephant revealed massive proliferation of Pasteurella bacteria that looked suspiciously like Bisgaard taxon 45.

Bacteria were found in a blood sample taken from one of the elephants / Photo: Chris Foggin

Despite all the research on the epidemic, the source of the infection and the way of transmission are unknown.

The most dramatic situation

Researchers described a case that resulted in the death of at least 11 elephants within 24 hours in an area of ​​50 square kilometers.

There had been several consecutive rainy seasons before the outbreak of the disease, but at the time of the mass deaths the region was in a state of drought. Researchers think that heat and drought may have somehow triggered bacteria that are normally harmless to animals to become contagious and spread among elephants.

Similar situations have already occurred. In 2015, another bacteria killed nearly 200,000 antelope in central Kazakhstan amid heat waves. And in 2019, elephants also died in Botswana during the hot season, but the reasons are also unknown.

But there are still many unanswered questions. “We don’t yet know how the bacteria got to this landscape; was it always there? Or was it commonly found in elephants but not noticed before?” – says Laura Rosen, veterinary epidemiologist and co-author of the study.

Victoria Falls Wildlife Trust now has equipment to test Bisgaard taxon 45. The organization plans to continue searching for this bacterium in elephants and large carnivores by examining samples from previous elephant deaths.