Case of anthrax in wildlife in the Namib Desert: Infected zebra most
likely causes death of three cheetahs

Date:
September 27, 2021
Source:
Leibniz Institute for Zoo and Wildlife Research (IZW)
Summary:
Anthrax is an infectious bacterial disease endemic in some parts of
Africa. It affects people, livestock as well as wildlife. Using GPS
telemetry data, a team of scientists reconstructed a special case
of anthrax infection in Namibia: Three free-ranging cheetahs in
the Namib Desert died within 24 hours after feeding on a mountain
zebra that tested positive for the disease. The zebra is the first
described case of a wild animal infected with anthrax in this arid
region. The case also shows that there might be previously unknown
risks to cheetah populations in the desert.



FULL STORY ========================================================================== Anthrax is an infectious bacterial disease endemic in some parts of
Africa. It affects people, livestock as well as wildlife. Using GPS
telemetry data, a team of scientists from the Cheetah Research Project
of the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) reconstructed a special case of anthrax infection in Namibia: Three free-ranging cheetahs in the Namib Desert died within 24 hours after
feeding on a mountain zebra that tested positive for the disease. The
zebra is the first described case of a wild animal infected with anthrax
in this arid region. The case also shows that there might be previously
unknown risks to cheetah populations in the desert. It is described in
detail in the scientific journal Frontiers in Veterinary Science.


========================================================================== Since 2015, scientists of the Leibniz-IZW Cheetah Research Project (CRP) conduct a National Cheetah Survey together with the Namibian Ministry
of Environment, Forestry and Tourism (MEFT). The purpose is to obtain
data on cheetah density and distribution across the country. Within
this framework, a coalition of three cheetah males was captured in the
Namib Desert and one animal equipped with a GPS collar. The recorded
location and movement data were regularly downloaded during aerial
tracking flights. On one of these flights, on October 5th 2019, the
carcass of a collared cheetah -- one of the members of the coalition --
was located from the aircraft. During the following ground inspection,
the other two cheetahs were also found dead. "The GPS data of the collared cheetah revealed that they died within a time window of six hours a few
days before we found them," says Ruben Portas, CRP scientist. "Evaluating
their most recent movements, we identified a cluster of GPS locations approximately two kilometres away from the location where they were
found dead." At this spot the cheetahs spent 20 hours on the day before
their death.

When visiting this cluster, Portas found the carcass of an adult mountain zebra. The GPS and activity data from the collar suggested that the
cheetahs fed on it. Bacillus anthracis, the cause of Anthrax infections,
was isolated from buccal and nasal swabs collected from the dead zebra,
making it the first confirmed anthrax infection in a wildlife species
in the Namib Desert.

Carnivores are typically less susceptible to anthrax than
herbivores. Cheetahs in particular have a high constitutive innate
immunity which provides them with a rapid first line of defence against pathogens such as Bacillus anthracis.

"However, when a high load of bacteria is ingested, for example with meat
from a contaminated carcass, their potent constitutive innate immunity
might be overloaded," explains CRP project head Bettina Wachter. "Cheetahs scavenge only rarely, which reduces their exposure to anthrax infected
prey. As a result, they do not produce high antibody titres, which would
be another line of defence. Thus, cheetahs die quickly when infected,
as studies in Etosha National Park in northern Namibia have shown."
The pathogen was not detected in any of the three cheetahs found in the
Namib, but the scientists consider it very likely that anthrax was the
direct cause of their death. 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. Additionally, 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.

Anthrax is an unstudied disease in arid habitats. When wildlife dies in
the Namib Desert, causes are often attributed to drought, hunger and the challenging desert conditions. "The few reported cases in which diseases
such as anthrax were tested in the arid environments of Namibia are when livestock or people were directly affected," says Portas. "We do not know
the prevalence of anthrax in the Namib desert and how wildlife populations
are affected by the disease. For other habitats, such as the Etosha
National Park, there is a large body of research showing that anthrax
has a key ecological role in the environment." This first confirmed
case of anthrax in the Namib Desert in wildlife demonstrates that the
disease might by endemic in the desert and other arid environments. Most
of the Namib Desert is included in protected areas where cheetahs and
other species find an important refuge from conflict with humans.

Thus, this new knowledge may be important for assessing risks to the
species.

"Although few data are available, no other disease has shown
such an impact on the cheetah population and certainly requires
further research that may lead to appropriate conservation
measures," Wachter concludes. "This study shows that data
recorded by GPS collars have the potential to disclose additional
important information in addition to spatial movement information." ========================================================================== Story Source: Materials provided by Leibniz_Institute_for_Zoo_and_Wildlife_Research_(IZW).

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Ruben Portas, Ortwin H. K. Aschenborn, Joerg Melzheimer, Manie
Le Roux,
Kenneth Heinrich Uiseb, Ga'bor A'rpa'd Czirja'k, Bettina
Wachter. GPS Telemetry Reveals a Zebra With Anthrax as Putative
Cause of Death for Three Cheetahs in the Namib Desert. Frontiers
in Veterinary Science, 2021; 8 DOI: 10.3389/fvets.2021.714758 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210927172904.htm

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