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African elephants suddenly dropped dead in 2020, and questions remain

A mystery surrounding the deaths of 35 African elephants in Zimbabwe is one step closer to being solved. New research suggests that a bacterium closely associated with deadly septicaemia is responsible for six of the deaths, as well as fatalities in neighboring countries.

Botswana mortality event

The casualties in Zimbabwe, which occurred in August and September of 2020, were preceded by the baffling deaths of approximately 350 elephants in northern Botswana just months earlier.

Government officials in Botswana said the deaths were caused by an unspecified cyanobacterial toxin, with no further details. Some of the affected elephants were observed walking in circles before literally dropping dead – often collapsing on their faces. 

Focus of the study 

In a unique collaboration, experts from the Victoria Falls Wildlife Trust, the Animal and Plant Health Agency UK, the University of Surrey, and South African laboratories set out to investigate.

“The sudden mortality of African elephants (Loxodonta africana) in Botswana and Zimbabwe in 2020 provoked considerable public interest and speculation,” wrote the study authors. 

“Poaching and malicious poisoning were excluded early on in the investigation. Other potential causes included environmental intoxication, infectious diseases, and increased habitat stress due to ongoing drought.”

Challenging investigation 

The team, led by Dr. Chris Foggin, faced challenges in identifying and examining the elephant carcasses. The experts had to consider initial suspicions of anthrax or other diseases posing risks to human health.

The complexity of conducting post-mortem examinations in field conditions on such large animals added to the difficulty of the investigation. 

“Investigating this mortality in the wildlife areas in north-west Zimbabwe proved challenging. Identifying and then reaching the carcasses in time to obtain useful samples is one problem we often face in this type of work,” explained Dr. Foggin.

“However, we also didn’t know what disease we may be dealing with, although we initially suspected that it could be anthrax, which is known to occur in the area; or possibly some other disease that might pose a risk to human health.”

“We therefore had to be cautious when undertaking the post-mortem examinations on elephant which, in itself, is a difficult task with such a big animal, especially working in field conditions.” 

New insights

Poaching was ruled out as a cause of death since the elephants’ tusks were intact, and toxicology analyses in Zimbabwe and the UK revealed no traces of poisons.

The breakthrough came when veterinarians and scientists identified a septicaemic infection caused by a little-known bacterium, provisionally named Bisgaard taxon 45, from the Pasteurellaceae family, in six elephants. 

This discovery was confirmed through bacterial isolation and genetic analysis, marking the first time this bacterium has been associated with elephant deaths. Limited sample availability restricted the extent of these examinations.

Study significance 

Professor Falko Steinbach, head of virology at APHA, emphasized the significance of identifying this bacterium and its potential for transmission, especially considering the social nature of elephants. 

“The identification of this bacterium is a significant step forward in learning more about why these elephants died, and I was pleased to be part of the team at APHA that could corroborate these important findings.,” said Professor Steinbach.

“Transmission of the bacteria is possible, especially given the highly sociable 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.”

“Further research is needed to learn more about the bacteria and its long-term implications for the African elephant population and other wildlife.” 

Study implications 

Dr. Arnoud van Vliet, senior lecturer in Veterinary Microbiology at the University of Surrey, highlighted the international collaboration in this research. The discovery of Bisgaard taxon 45’s role in bacterial septicaemia adds to the growing list of threats to elephant conservation.

The African savanna elephant is already an endangered species with an estimated 350,000 remaining in the wild and an ongoing eight percent annual population decline.

The research not only uncovers a potential cause of the recent mysterious deaths but also emphasizes the importance of continued investigation for the future of African elephants.

This research is published in the journal Nature Communications.

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