During May and June of 2020, there was a puzzling event in Botswana’s Okavango delta where 350 elephants passed away, leaving conservationists and the world wondering about the cause. The victims were of various ages and genders, exhibiting strange behavior such as walking in circles before suddenly collapsing on their faces. A similar incident occurred two months later in north-western Zimbabwe, resulting in 35 more elephant deaths.
According to government officials, the deaths in Botswana were blamed on a cyanobacterial toxin, but no specific information was released at the time.
However, the results of tests conducted on the deceased elephants in Zimbabwe have revealed that the cause of death was a lesser-known bacterium known as Pasteurella Bisgaard taxon 45. This bacterial infection led to septicaemia, also known as blood poisoning.
A recent study published in the journal Nature Communications reports that the bacterial infection, which has not been previously associated with elephant deaths, may have been the cause of deaths in nearby countries.
The paper, written by a team of researchers from the Victoria Falls Wildlife Trust, the University of Surrey, laboratories in South Africa, and the UK government’s Animal and Plant Health Agency (APHA), highlights a significant conservation issue for elephants in the largest remaining population of this endangered species.
The population of African savanna elephants is decreasing at a rate of 8% annually, mainly because of poaching. There are currently 350,000 elephants remaining in their natural habitat. The research recommends including infectious diseases as one of the factors contributing to their decline.
According to Dr. Arnoud van Vliet, a researcher at the University of Surrey, the infection is another concern for the conservation of elephants, which are already facing numerous threats from diseases. Elephants are known for their social nature and the drought conditions during the time may have added to their stress, making them more susceptible to this type of outbreak.
Pasteurella bacteria has previously been linked to the sudden death of about 200,000 saiga antelopes in Kazakhstan – an incident that researchers believe could shed light on what happened to the elephant herds. Scientists believe the Pasteurella bacteria generally lives harmlessly in the tonsils of some, if not all, of the antelopes. An unusual temperature increase to 37C, however, caused the bacteria to pass into the bloodstream, where it caused septicaemia.
According to the paper, previous research has shown that the Bisgaard taxon 45 is present in tigers and lions (discovered through testing a human bite wound), as well as chipmunks and psittacines.
Experts also examined for cyanide, a substance sometimes used to harm elephants, but no poisons were found in the carcasses or surrounding waterholes. Another hypothesis was that the elephants had consumed toxins from algal blooms. Poaching was quickly ruled out as the tusks were still intact on the carcasses.
Dr. Chris Foggin, a wildlife veterinarian at the Victoria Falls Wildlife Trust and the lead investigator, described the investigation of the mass deaths as a difficult task.
“The challenges we frequently encounter include identifying and promptly accessing the carcasses for obtaining valuable samples. Additionally, there was uncertainty regarding the potential illness we were dealing with,” he stated.
At first, we thought it could be anthrax, a disease known to be prevalent in the area. There was also a possibility of another disease that could be harmful to humans. As a result, we proceeded with caution during the postmortem examinations of the elephants. This was a challenging task, given their large size and the field conditions we were working in.
The researchers could not physically go to the location in Botswana nearby, so they gathered most of their samples from decaying animals. According to the article, the discovery of blood poisoning suggests that this issue may be occurring continuously in this area, as past instances were not detected due to inadequate testing.