A study conducted by an international organization investigating the unexplained deaths of 35 African elephants in Zimbabwe has found that a bacterium associated with fatal sepsis, named Bisgaard taxon 45, may be involved. The discovery highlights the growing threats facing the African elephant, an endangered species, and underscores the importance of further studying these causes of mortality to ensure the species' survival.
A bacterium linked to severe sepsis may be responsible for the deaths of six African elephants in Zimbabwe and may be responsible for the deaths of other African elephants in nearby countries. The discovery adds infectious diseases to the growing list of challenges African elephants face, with their populations still in jeopardy.
In this unique study, scientists from the Victoria Falls Wildlife Trust, the UK's Animal and Plant Health Service, the University of Surrey and the South African Laboratory investigated the mysterious deaths of 35 elephants, mostly between August and September 2020, within a 40x25km radius in northwest Zimbabwe. Prior to this, about 350 elephants died in northern Botswana in neighboring Botswana between May and June 2020, which attracted widespread attention from the international community.
African savanna elephants are an endangered species, with only 350,000 remaining in the wild and annual losses estimated at 8%. The discovery is deeply worrying as elephants are listed on the International Union for Conservation of Nature's Red List. Investigating the causes of these elephant deaths is vital to protecting the future of this magnificent species.
Lead investigator Dr Chris Foggin, wildlife veterinarian at Victoria Falls Wildlife Trust, said;
"Investigating this death in a game reserve in northwest Zimbabwe is extremely challenging. A problem we often face in this type of work is how to detect and reach the carcass in time to obtain useful samples. However, we also did not know what diseases we might have encountered, although we initially suspected it might be Anthrax, as it is known to occur in the area; or possibly some other disease that may pose a threat to human health. So we have to be careful when performing necropsies on elephants because performing a necropsy on such a large animal is a difficult task in itself, especially working in wild conditions."
Research findings and implications
Several necropsies were performed on the elephants. The possibility of poaching was quickly ruled out, mainly because all the dead elephants' tusks were intact. Toxicological analyses, including point-of-care tests for cyanide, which is sometimes used to kill elephants in Zimbabwe, and more sophisticated analyzes in the UK found no traces of poison in the elephant carcasses or in the waterholes near many of the carcasses.
Further examination by veterinarians and scientists revealed that six elephants were infected with septicemia caused by a little-known bacterium tentatively named Bisgaard taxon 45, an unclassified member of the Pasteurellaceae family of bacteria. Bacterial isolation and genetic analysis confirmed this. Only a limited number of samples are suitable for such examination. Pasteurella has been previously linked to sudden deaths in wild animals such as antelopes, but prior to this study, Pasteurella was not suspected of being involved in elephant deaths.
Professor Falko Steinbach, Head of Virology at APHA said:
"The identification of this bacterium is an important step in further understanding the cause of death in these elephants, and I am delighted to be part of the APVA team confirming these important findings. It is possible that this bacterium is spread, especially given the highly social nature of elephants, and the link between this infection and the stress associated with extreme weather events such as drought, which may make outbreaks more likely to occur. Further research is needed to further understand this bacterium and its long-term effects on African elephant herds and other wildlife."
Dr Arnoud van Vliet, Senior Lecturer in Veterinary Microbiology at the University of Surrey’s School of Veterinary Medicine, said:
"The international composition of our research team highlights the opportunities presented by conservation investigations of disease and mortality in free-ranging animals. Bisgaard taxon 45 has never been previously associated with bacterial sepsis, and it adds to the list of disease-related threats to elephant conservation."