In the middle of 2020, the sudden demise of 350 elephants in Botswana’s Okavango delta left the conservation community puzzled and stirred global intrigue. Disturbingly, these elephants, irrespective of age or gender, exhibited unusual behavior, like walking in circles, before collapsing and dying. A subsequent incident in Zimbabwe saw 35 more elephants perish.
Initial explanations for the Botswana incident pointed to a cyanobacterial toxin, but no comprehensive details were provided. However, recent tests on the elephants from Zimbabwe have identified the culprit: a bacterium named Pasteurella Bisgaard taxon 45, which induced septicaemia or blood poisoning.
This bacterial infection, as highlighted in the Nature Communications journal, had not been previously associated with elephant fatalities. The research suggests that this bacterium might also be behind the deaths in Botswana.
The study underscores the significance of this discovery for the conservation of elephants, especially given their endangered status. Authored by a global team of experts, the paper emphasizes the mounting threats elephants face, including infectious diseases.
With African savanna elephants’ numbers dwindling by 8% annually, primarily due to poaching, the study recommends adding infectious diseases to their list of threats.
Dr. Arnoud van Vliet from the University of Surrey highlighted the added risk, noting that the sociable nature of elephants, combined with the stress from drought conditions, could have exacerbated the outbreak.
Interestingly, Pasteurella bacteria had been previously linked to the abrupt death of around 200,000 saiga antelopes in Kazakhstan. A temperature spike was believed to have activated the bacteria, leading to septicaemia. The Bisgaard taxon 45 variant has also been detected in tigers, lions, chipmunks, and psittacines.
While experts considered various potential causes, including cyanide poisoning and toxins from algal blooms, these were ruled out. The presence of tusks on the carcasses also negated the possibility of poaching.
Dr. Chris Foggin, the lead investigator from the Victoria Falls Wildlife Trust, described the investigation as “challenging.” The initial suspicion was anthrax, a known local threat, or another disease potentially harmful to humans. The postmortem examinations, especially in field conditions, posed significant challenges.
The inability to visit the Botswana site and the decayed state of most official samples added to the complexity. The study suggests that such incidents of blood poisoning might be recurrent in this region, with previous cases possibly overlooked due to inadequate testing.