On October 5th 2019, the carcass of a GPS-collared cheetah in the Namib desert was found dead from the air. After they went in on foot to investigate, two other cheetahs were also found dead. The GPS data showed they had all died within a short period of each other so the team then identified a cluster of GPS locations approximately two kilometers away from the location where they were found dead.
At that spot, they found the carcass of an adult mountain zebra, which the cheetahs had likely fed on. Buccal and nasal swabs found Bacillus anthracis, the cause of Anthrax infections, making it the first confirmed anthrax infection in a wildlife species in the Namib Desert. Nature is out to kill us all, and cheetahs are no exception any more than the zebra was.
Yet they couldn't actually detect anthrax in the cheetahs. Bacterial cultures from highly susceptible animals that quickly die are often anthrax negative, because the animals might die already at a low presence of bacteria in the blood or from a high load of toxin released by Bacillus anthracis when destroyed by the immune system. The vegetative form of the pathogen only develops when exposed to air quickly after the death of the host. The cheetahs were untouched for 11 days after their death and their bodies were not opened by scavengers, which might also explain the negative results of the lab tests for anthrax.
And varnivores are typically less susceptible to anthrax than herbivores. Cheetahs have a high constitutive innate immunity which provides them with a rapid first line of defense against pathogens such as Bacillus anthracis. A first line of defense can be overrun by a high load of bacteria, like meat from a contaminated carcass, and since cheetahs rarely scavenge, they do not produce high antibody titres, which would be another line of defense.
Citation: Portas R, Aschenborn OHK, Melzheimer J, Le Roux M, Uiseb KH, Czirják GÁ, Wachter B (2021): GPS telemetry reveals a zebra with anthrax as putative cause of death for three cheetahs in the Namib desert. Frontiers in Veterinary Science 8:714758. DOI: 10.3389/fvets.2021.714758
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