More than 400 African savannah elephants (Loxodonta Africana) died between March and September 2020 in Zimbabwe and Botswana in one of the most tragic and mysterious episodes recorded in recent decades by what is considered the largest land animal that inhabits the Earth in the present.
In a single week in August, 22 carcasses of these animals were recorded in the Panda Masuei forest reserve, in Zimbabwe.
Poaching was initially ruled out as the cause of the deaths, since the corpses kept their fangs intact. Drought, lack of food or the presence of some contaminant or poison in the region's waters were then considered, but it was not possible to determine a common origin. In the case of the deaths in Botswana, preliminary data from an investigation indicated that the elephants had been affected by a bloom of cyanobacteria in the water.
The systematic study of several samples of the deceased animals, in an investigation that has lasted almost two years, has led to the conclusion that the vast majority of deaths were due to septicemia (the body's response to the presence of bacteria in the blood) by infection with a particularly aggressive strain of the bacteria Pasteurella multocida, known to scientists as Bisgaard taxon 45.
The results of this research have been published (October 25) in the journal Nature Communications and represent an important advance in the work for the conservation of this endangered species.
Most of the samples analyzed were from elephants killed in northwest Zimbabwe between August and September 2020, although scientists from the Victoria Falls Wildlife Trust, the UK Animal and Plant Health Agency, the University of Surrey and laboratories from South Africa that have participated in the work consider that the results can be extended to a good part of the elephants that died in similar circumstances in this country and in Botswana throughout the year 2020.
African savanna elephants are an endangered species; There are only 350,000 left in the wild and current losses are estimated at 8% annually.
Chris Foggin, wildlife veterinarian at the Victoria Falls Wildlife Trust and lead author of the new study, explained that "investigating this mortality proved to be a challenge, among other reasons due to the difficulty of identifying the carcasses, taking samples and transporting them in safe conditions." to obtain useful data," as explained in statements released by the University of Surrey.
"In addition, we also did not know what disease we might be facing. Initially, we suspected that it could be anthrax, which is known to be present in the area or some other disease with a risk to human health. Therefore, we had to be cautious when perform post-mortem examinations on elephants, which, in itself, is a difficult task with such a large animal, especially when working in field conditions," says this researcher.
Toxicological analysis, including immediate tests for cyanide, which is sometimes used to kill elephants in Zimbabwe, as well as more sophisticated analyzes carried out in the United Kingdom, found no traces of poison in the carcasses or in a water hole near many of the corpses.
Further examination by veterinarians and scientists identified a septicemic infection caused by a little-known bacteria provisionally called Bisgaard taxon 45, an unclassified member of the bacterial family Pasteurellaceae, in six elephants. This was confirmed by bacterial isolation and genetic analysis.
Pasteurella bacteria have previously been implicated in sudden deaths of wild animals such as antelopes, but before this study their relationship with elephant deaths was not suspected.
Professor Falko Steinbach, head of virology at APHA, highlights that "the identification of this bacteria is an important step forward in learning more about why these elephants died." "More research is needed to learn more about the bacteria and its long-term implications for the population of African elephants and other wildlife."
Arnoud van Vliet, Senior Lecturer in Veterinary Microbiology at the University of Surrey's School of Veterinary Medicine, said: "Bisgaard's taxon 45 has never before been associated with bacterial septicemia and adds to the growing list of disease-related threats. for elephant conservation.
