Mycobacterium bovis in a Free-Ranging Black Rhinoceros, Kruger National Park, South Africa, 2016

Abstract

In 2016, an emaciated black rhinoceros (Diceros bicornis) was found in Kruger National Park, South Africa. An interferon-γ response was detected against mycobacterial antigens, and lung tissue was positive for Mycobacterium bovis. This case highlights the risk that tuberculosis presents to rhinoceros in M. bovis–endemic areas.

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Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 23, No. 3, March 2017 557
RESEARCH LETTERS
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Mycobacterium bovis in a
Free-Ranging Black
Rhinoceros, Kruger National
Park, South Africa, 2016
Michele A. Miller,1 Peter E. Buss,1
Paul D. van Helden, Sven D.C. Parsons
Author aliations: Stellenbosch University, Cape Town,
South Africa (M.A. Miller, P.D. van Helden, S.D.C. Parsons);
South African National Parks, Skukuza, South Africa (P.E. Buss)
DOI: http://dx.doi.org/10.3201/eid2303.161622
In 2016, an emaciated black rhinoceros (Diceros bicor-
nis) was found in Kruger National Park, South Africa.
An interferon-γ response was detected against mycobacte-
rial antigens, and lung tissue was positive for Mycobacte-
rium bovis. This case highlights the risk that tuberculosis
presents to rhinoceros in M. bovis–endemic areas.
Black rhinoceros (Diceros bicornis) are under severe
threat from poaching and habitat loss. This species
has been designated as critically endangered by the In-
ternational Union for Conservation of Nature Red List
(1). An estimated population of 5,000–5,445 animals are
found in southern and eastern Africa, with just over 1,200
of those in South Africa (2). In Kruger National Park
(KNP) in South Africa, the black rhinoceros population
size is estimated at 400. KNP is considered an endemic
area for Mycobacterium bovis, with cases reported in at
least 12 wildlife species, including African bualo, lion,
kudu, and warthog (3).
Sporadic cases of tuberculosis (TB) caused by M. tu-
berculosis or M. bovis have been reported in black rhinoc-
eros housed in zoos or under semi-intensive management
(4). Although M. bovis is present in livestock and other
wildlife species in countries in Africa where rhinoceros
populations are currently present, no cases of TB have been
reported in free-ranging black rhinoceros.
On June 17, 2016, rangers in KNP reported a weak,
emaciated, adult female black rhinoceros that had been
stationary for 36 hours in the southern area of the park
(25°7′16′′S, 31°55′2′′E). The discovery of this animal
might have resulted from increased surveillance related
to poaching. When veterinary sta arrived, the rhinoceros
was unresponsive and recumbent and lifted its head only
when darted. External injuries were not obvious. Because
of its poor prognosis, the animal was euthanized after
being immobilized. Postmortem evaluation revealed an
emaciated animal (body condition score 1 out of 5, http://
www.da.qld.gov.au/__data/assets/pdf_le/0015/53520/
Animal-HD-Investigation-Condition-scores.pdf) with a
subjectively heavy ectoparasite load. The subcutaneous
and internal fat stores were reduced, consistent with the
poor general body condition. Although teeth were worn,
they appeared sucient for mastication, and well-chewed
ingesta was found in the gastrointestinal system. No
grossly abnormal changes were found in the organs exam-
ined, except for the lungs and lymph nodes. On palpation
of the lungs, numerous rm, focal, and irregular masses,
1–6 cm in diameter, were present in the right and left
dorso-cranial two thirds of the lung lobes, with symmet-
ric lesion distribution. On cut section, most lesions had a
brous capsule and contained creamy necro-caseous ma-
terial. Impression smears from the lung lesions revealed
numerous acid-fast bacilli.
1These authors contributed equally to this article.

The heparinized whole blood samples that were col-
lected before the animal was euthanized were incubated
in Nil and TB Antigen tubes of the QuantiFERON TB
Gold In-Tube system (QIAGEN, Venlo, Netherlands) and
with pokeweed mitogen (Sigma-Aldrich Pty., Ltd., Johan-
nesburg, South Africa) as a positive control. After 24 h,
plasma was harvested and interferon-γ (IFN-γ) was mea-
sured in these samples by using a bovine IFN-γ ELISA
(Mabtech AB, Nacka Strand, Sweden) as previously de-
scribed for African bualoes (5). IFN-γ concentrations
measured in the sample from the Nil tube, pokeweed
mitogen tube, and TB Antigen tube were 4 pg/mL, 753
pg/mL, and 175 pg/mL, respectively. The TB antigen-
specic release of IFN-γ was consistent with immuno-
logic sensitization to M. bovis or M. tuberculosis (5). We
detected no antibodies to the M. bovis antigens MPB83
or ESAT6/CFP10 complex in serum samples tested with
the Dual Path Platform VetTB assay (Chembio Diagnos-
tic Systems, Inc., Medford, NY, USA) (6). PCR analyses
conrmed M. bovis infection, both directly from the lung
tissue and indirectly from mycobacteria culturing of lung
tissue samples, as previously described (7,8).
Because black rhinoceros have been shown to be sus-
ceptible to TB, it is not unexpected to diagnose bovine TB
in a free-ranging rhinoceros in an area with a high preva-
lence of TB in other wildlife species (4). Risk factors such
as environmental load of mycobacteria, presence of con-
current disease, and other stressors (including malnutrition
associated with drought) might result in progression of M.
bovis infection. Although the source of infection for the
animal we describe is unknown, no known exposure to hu-
mans or livestock has occurred. It is possible that interac-
tion with other infected wildlife, including African bualo,
which are considered maintenance hosts of bovine TB, or
environmental contamination at shared water holes and
feeding sites might have resulted in pathogen contact (8,9).
Occurrence of M. bovis infection in a free-ranging
black rhinoceros in KNP might have substantial conse-
quences for conservation programs. The risk for disease
transmission between isolated, small populations of criti-
cally endangered species could hinder future transloca-
tion of these animals. Further risk assessments are needed
to investigate the importance of this nding.
Acknowledgments
We acknowledge South African National Parks sta, especially
Leana Rossouw, Guy Hausler, and Tebogo Manamela, for
providing assistance with this case, as well as the State
Veterinary Services of Kruger National Park.
Research protocols were approved by the South African National
Park Animal Use and Care Committee. This study was supported
by the National Research Foundation South African Research
Chair Initiative in Animal Tuberculosis (grant no. 86949).
Dr. Miller is currently the South African Research Chair in Animal
Tuberculosis in the National Research Foundation Centre of
Excellence for Biomedical Tuberculosis Research at Stellenbosch
University. She investigates multiple aspects of animal TB.
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Address for correspondence: Michele A. Miller, DST/NRF Centre of
Excellence for Biomedical TB Research/MRC Centre for Tuberculosis
Research/Division of Molecular Biology and Human Genetics, Faculty
of Medicine and Health Sciences, Stellenbosch University, PO Box 241,
Cape Town 8000, South Africa; email: miller@sun.ac.za
558 Emerging Infectious Diseases • www.cdc.gov/eid • Vol. 23, No. 3, March 2017
RESEARCH LETTERS