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Bull Vet Inst Pulawy 59, 483-487, 2015
DOI:10.1515/bvip-2015-0072
DE GRUYTER
OPEN
Avian tuberculosis
in a captive cassowary (Casuarius casuarius)
Monika Krajewska1, Agnieszka Czujkowska2, Marcin Weiner3,
Marek Lipiec1, Krzysztof Szulowski1
1Department
of Microbiology, National Veterinary Research Institute, 24-100 Pulawy, Poland
2Warsaw Zoological Gardens, 03-461 Warsaw, Poland
3Pope John Paul II State School of Higher Education in Biała Podlaska, 21-500 Biała Podlaska, Poland
[email protected]
Received: August 24, 2015
Accepted: November 23, 2015
Abstract
The paper describes avian tuberculosis in a captive bred cassowary. A two-and-a-half-year-old bird was obtained by
a Polish zoo in 2010 from the Netherlands under conditions compliant with the recommendations of the European Association of
Zoos and Aquaria. Despite being of small size for the age, the bird appeared healthy and showed no signs of the disease until the
day when it was found recumbent in its pen. Later on it was euthanised due to lack of treatment possibilities. Pathological
changes typical of avian tuberculosis were found in the liver and spleen. Mycobacterium avium ssp. avium was cultured from
both organs.
Keywords: cassowary, avian tuberculosis, Mycobacterium avium ssp. avium, zoo.
Introduction
Mycobacteria include a group of over 140
atypical bacteria described as mycobacteria other
than tuberculosis (MOTT) or non-tuberculous
mycobacteria (NTM) (15). There is a continual
increase in the number of identified mycobacteria
species due to the development of molecular methods
(23). Due to the constant presence of mycobacteria in
the environment, people and animals are continually
exposed to MOTT. Mycobacterial infection is an
infectious disease which can affect all animal species:
fish, reptiles, birds, and mammals (2, 4, 8, 10, 22).
Mycobacterium avium, which in birds causes typical
tuberculosis, is also pathogenic to immunodeprived
humans and other animals, causing a disease known
as mycobacteriosis.
Cassowaries belong to the superfamily which
includes three species of land and flightless birds.
They live in New Guinea and north-eastern Australia,
and the islands have had them in included in the Red
List of Threatened Species. One example of such
a vulnerable species is the Australian Southern
cassowary (Casuarius casuarius johnsonii) which is
endemic to the north-western area of Queensland in
Australia (1). The population of these birds is
endangered due to habitat destruction, road kills, dog
attacks, hand feeding, diseases, and cyclones (9).
Material and Methods
Case description. A two-and-a-half-year-old
male bird was obtained by the Warsaw Municipal
Zoological Garden in 2010 from the Netherlands
under conditions compliant with the recommendations
of the European Association of Zoos and Aquaria.
From the beginning it showed stunted growth and
minor anatomical abnormalities: a deformed jaw and
deformation in the crop area, which was thought to be
due to hand rearing and the character of the bird. The
veterinarian attending the cassowary was informed of
its unusual calm behaviour. There were no other
symptoms such as lack of appetite or more solid
faecal consistency. In few days, the bird started to
behave normally. About a month later, the cassowary
was found recumbent with breathing problems and
was easily approachable by the staff. A clinical
examination of the bird demonstrated that the
oesophagus and crop seemed to be extended.
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Ketamine (2 mg/20 kg) and xylazine (2 mg/kg) were
used for sedation of the bird and then the animal was
intubated and supported by inhalation anaesthesia
using a mixture of oxygen and isofluorane (1.5%–
2.5% support concentration). The lateral skin was
incised and a thick, brown, amorphous mass was seen,
which was not directly related to the oesophagus.
Further examination showed that the mass consisted
of coagulated blood. The changes were considered
inoperable and the veterinarian decided to euthanise
the bird.
Microbiology. Material from the liver and spleen
was taken for microbiological analysis. The
examination was performed in accordance with the
OIE Manual (Chapter 2.3.6: Avian tuberculosis). The
material was then homogenised in a 5% solution of
oxalic acid. The resulting supernatant was removed
and the pellet was washed twice with sterile
physiological saline. The rinsed pellet was used for
inoculation of culture media, which was three
Stonenbrinck’s slants and three Petragnani medium
slants, and incubated at 37°C.
Microscopy. The cultures from all slants were
stained with Ziehl–Neelsen stain and examined for
acid-fast bacilli.
Identification. The typing of the isolated
Mycobacterium was performed by GenoType CM®
(HAIN Lifescience, Germany). The test comprises 38
molecular models, 24 of which can be assigned to
different species of mycobacteria, 10 patterns
correspond to two or more species and 4 correspond
to the patterns of Mycobacterium spp. or grampositive bacteria with high G-C pair contents of the
genome (16, 17, 18). The analysis consisted of three
main stages: isolation of DNA from the isolated
strain, amplification of genetic material by using
biotinylated primers, and hybridisation. The results
were shown on nitrocellulose strips in the form of
dark bands arranged in a specific configuration.
Comparison of strips with patterns included by the
manufacturer led to their differentiation and the
typing of the isolated Mycobacterium.
Results
Post-mortem examination did not reveal any
changes in the respiratory or nervous systems, nor the
pancreas. The liver was enlarged, brittle, and dark
brown with numerous suppurative granulomas from 1
to 4 mm in size, which were observed on the surface
of the organ and in the cross-section (Fig. 1). The
spleen was of friable consistency, pale green to darkred, and almost totally covered with granulomatous
lesions (Fig. 2). The kidneys were enlarged and darkred coloured. There were no changes in the mucosa of
the crop or oesophagus. The stomach was correctly
filled and gastric mucosa was not congested. Intestinal
mesenteric lymph nodes were extremely enlarged to
the size of ping-pong balls. The bursa of Fabricius
was the same size.
After about 20 d, abundant growth of the
Mycobacterium was observed on both media.
Examination confirmed the presence of acid-fast
bacteria in all preparations (Fig. 3). The results of
genotyping showed that the isolated strain was
classified as Mycobacterium avium spp. avium.
Fig. 1. The brittle, dark-brown liver with numerous suppurative granulomas
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485
Fig. 2. The pale green to dark-red spleen with granulomatous lesions
Fig. 3. The microscopic picture of acid-fast bacilli (Ziehl–Neelsen stain)
Discussion
Avian tuberculosis is an infectious disease of all
species of exotic, wild, and domestic birds, caused by
Mycobacterium avium (5, 7). It is a chronic debilitating
disease that can persist for years in an infected flock.
Initially clinical signs of infection are absent, with no
changes in appetite or growth rates. As the disease
progresses there is a gradual emaciation, with preserved
appetite. The condition of the birds deteriorates and in
many cases lameness and diarrhoea are observed.
Birds die due to extreme exhaustion. The following
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M. Krajewska et al./Bull Vet Inst Pulawy/59 (2015) 483-487
diseases should be considered in the differential
diagnosis of avian tuberculosis: yersiniosis, avian
pseudotuberculosis, coligranulomatosis, listeriosis,
histomoniasis, aspergillosis, and cancer.
The literature data shows that we know a lot about
viral and bacterial infections of fowl in Poland (3, 6,
11, 21). Wild birds living outside as well as inside zoos
are also a subject of interest to many Polish research
centres (12). Unfortunately, obtaining test samples
from wild specimens is not as easy as from those kept
on poultry farms. The subject of M. avium infections in
poultry and wildfowl in Poland seems to be somewhat
neglected. It should be emphasised that avian
tuberculosis causes typical pathological changes in the
bird’s liver and spleen, which is why the majority of
fatal cases in zoos are rarely further investigated in the
reference laboratory. This confirms the opinion that
tuberculous lesions in the lungs are rare in cases of
M. avium infection in birds (2). Numerous acid-fast
structures represent a further positive result of
microscopic examination and are sufficient to dispel
any doubt in making the diagnosis (Fig. 3). Avian
tuberculosis is typically a chronic disease, very
frequently secondary to other health issues (20). Some
species seem to be more prone to this disease, and the
cassowary is a great example of a ground-feeding
species that has more potential means of exposure to
mycobacterium species, but which should be more
resistant. Numerous studies show (2, 20) that exposure
to tuberculosis infection correlates closely with the
concentration of infectious particles and time of
exposure. Therefore, birds remaining together in close
and lasting contact are more exposed to infection,
which obviously relates to birds living in pairs or
sharing enclosures with pest species like sparrows,
pigeons, Corvidae, or peacocks (free ranging in many
zoos) that cannot be completely eliminated. Antemortem diagnosis includes PCR, ELISA, or intradermal
tuberculin skin test. During clinical examination special
care should be taken to examine the oral cavity for
plaques that may be related to the disease. Birds that
are positive should be culled due to their zoonotic
potential.
The most common disease in the cassowary is
avian tuberculosis (14). According to Pavlik et al. (13)
there are also other mycobacterial infections like
Mycobacterium bovis which cause the death of birds.
However, the total reported number of cassowary
deaths due to diagnosed diseases is very low (9).
M. avium infection should be regarded as a candidate
diagnosis in chronic weight loss and emaciation,
although it is hard to notice in non-flying birds as the
pectoral muscles are relatively small (20). Avian
tuberculosis is a possible threat to zoo- and free-living
populations of cassowaries. The role of the cassowary
in the spread of M. avium and other types of
tuberculosis complex infection should be considered in
animal collections like zoological gardens.
Conflict of Interests Statement: The authors declare
that they do not have any financial or non-financial
conflict of interests regarding the publication of this
article.
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