Transboundary and Emerging Diseases
SHORT COMMUNICATION
Isolation of Brucella abortus from a Dog and a Cat Confirms
their Biological Role in Re-emergence and Dissemination of
Bovine Brucellosis on Dairy Farms
G. Wareth1,2, F. Melzer1, M. El-Diasty3, G. Schmoock1, E. Elbauomy4, N. Abdel-Hamid4, A. Sayour4 and
H. Neubauer1
1
2
3
4
Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, Institute of Bacterial Infections and Zoonoses, Jena, Germany
Faculty of Veterinary Medicine, Benha University, Moshtohor, Egypt
Animal Health Research Institute-Mansoura Provincial Laboratory, Mansoura, Egypt
Animal Health Research Institute, Giza, Egypt
Keywords:
Brucella abortus; Bovine brucellosis; dogs;
cats; re-emerging; spillover; Egypt
Correspondence:
G. Wareth. Friedrich-Loeffler-Institut, Federal
Research Institute for Animal Health, Institute
of Bacterial Infections and Zoonoses,
Naumburger Str. 96a, 07743 Jena, Germany.
Tel.: +4915779564050; Fax:
+4936418042228; E-mail:
[email protected]
Summary
Brucellosis is highly contagious bacterial zoonoses affecting a wide range of
domesticated and wild animals. In this study, Brucella (B.) abortus bv 1 was identified in uterine discharge of apparently healthy bitch and queen with open
pyometra housed on a cattle farm. This study highlights the role of dogs and cats
as symptomatic carriers and reservoirs for Brucella. To the best of our knowledge,
this study represents the first report of feline infection with B. abortus bv 1 globally. These pet animals may contaminate the environment and infect both livestock and humans. Surveillance and control programmes of brucellosis have to
include eradication of the disease in dogs, cats and companion animals.
Received for publication February 16, 2016
doi:10.1111/tbed.12535
Background
Brucellosis is an incapacitating zoonosis in humans and an
economically disastrous disease in farm animals caused by
Brucella spp. Bovine brucellosis is a worldwide-occurring
zoonosis affecting cows, buffaloes and wildlife species. The
causative agent is mainly Brucella (B.) abortus. Even though
it has been eradicated from farm animals in many countries, in politically instable areas infection is re-emerging in
livestock and consequently in humans (Corbel, 1997; Russo
et al., 2009). In Egypt, brucellosis is prevalent nationwide
in all farm animal species and in the environment.
B. melitensis biovare (bv) 3 and less frequently B. abortus
bv 1 are the predominate isolates which have been isolated
from livestock, Nile catfish and from carrier hosts, for
example rats (Wareth et al., 2014) and dogs (Hosein et al.,
2001). The transmission of brucellae from wildlife to farm
animals has been proven and spillover from livestock to
wildlife has occurred (Godfroid, 2002; Truong et al., 2011,
2013). The role of pet animals on farms as reservoir has not
been carefully studied in Egypt, yet. This study aimed to
identify Brucella spp. in a seropositive bitch and a queen
housed on an infected dairy cattle farm and to elucidate
their potential role in maintaining the infection.
Materials and Methods
A dairy cattle farm with a total number of 500 Holstein
cows and heifers located in Damietta governorate at the
north costal region of Egypt had a history of brucellosis.
The male animals in the farm were kept in a separate section for meat production. The farm suffered from brucellosis and the prevalence of brucellosis before control
measures was around 7%. Following the current control
programmes adopted by the General Organization for
Veterinary Services (GOVS), all positive bovines were
culled or slaughtered. Briefly, all cows, heifers and bulls
were tested by rose bengal test (RBT) and serum
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agglutination test (SAT) followed by complement fixation
test (CFT) and enzyme-linked immunosorbent assay
(ELISA) as confirmatory tests. Blood samples and samples
of uterine discharge from dams, foetal tissues and stomach
content from all aborted fetuses were cultured. B. abortus
bv 1 was isolated from aborted cows. The farm was released
from quarantine after three successive negative results in
serology with 1-month intervals. Then, several cases of
abortion were observed on the farm and brucellosis reemerged again. Two queens including one with open
pyometra and one bitch that had aborted yet were housed
on the farm and were in close contact with cattle and the
automatic milking facility (Fig. 1). Blood samples collected
from the bitch and the queen with open pyometra gave
strong positive reactions using standard agglutination test.
Samples of uterine discharge collected from the seropositive
bitch and queen as well as from aborted cows were cultivated. Brucella identification and biotyping were performed
based on colonial morphology, microscopic appearance,
biochemical tests, CO2 requirement, H2S production,
growth in the presence of the dyes thionine and fuchsine,
agglutination with monospecific antisera and phage lysis
(Alton et al., 1988). Following heat inactivation of bacteria
at 80° for 2 h, DNA was extracted with the High Pure PCR
template preparation kit (Roche Applied Sciences; Mannheim, Germany) according to the manufacturer’s instructions. The AMOS-PCR (B. abortus, B. melitensis, B. ovis
and B. suis-PCR) was used (Bricker and Halling, 1994).
Genotyping analysis of isolates using multiple locus of variable number tandem repeats analysis (MLVA-16) was performed (Le Fleche et al., 2006).
Results and Discussion
Fig. 1. Two cats drinking milk inside the automatic milking room of
the infected farm.
Bovine brucellosis, caused mainly by the bacterium
B. abortus, is an economically important zoonosis due to
abortions in cattle. It also affects other hosts including buffalo, bison and wildlife. In this study, one strain of Brucella
was isolated from a bitch and a queen with open pyometra,
respectively. The molecular and bacteriological examination identified the bacterium as B. abortus bv 1. As shown
in Fig. 2, B. abortus isolates from the bitch and queen (ID:
15RB7429 and 15RB7430) have the same genotype as
strains recovered from a cow of the same farm (ID:
15RB7432) and from cattle of the same region (ID:
14RB5309, 14RB5311and 14RB5312). Two isolates of Trueperella spp. were also recovered from the bitch and cat
(data not shown). These opportunistic bacteria might have
Fig. 2. Neighbour-joining analysis for the MLVA-16 profiles of Brucella abortus strains isolated from a bitch and a cat compared with isolates recovered from cattle in Egypt. Panel 1 includes eight minisatellite markers and Panel 2 is composed of eight microsatellite markers. The corresponding cells
contain numbers of tandem repeats.
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First B. abortus from Dog and Cat in Egypt
G. Wareth et al.
been the cause of abortion and open pyometra seen in the
bitch and queen, respectively (Ribeiro et al., 2015).
A rapidly increasing population of housed and stray dogs
and cats in Egypt has caused concern regarding transmission of zoonotic diseases. Dogs are the preliminary and natural host species for B. canis (Greene and Carmichael,
2013). B. canis is one of the most important bacterial infections causing abortion in the bitches, but it is uncommon
in queens (Pretzer, 2008). Dogs can be infected also by
B. suis, B. melitensis and B. abortus. The clinical signs of
brucellosis in dogs range from asymptomatic course to
abortion (Hollett, 2006; Ramamoorthy et al., 2011). Transmission of B. abortus from cattle to dogs has been
suspected due to positive RBT (Cadmus et al., 2011) or
Bruce-ladder PCR results (Truong et al., 2011). There has
been an early attempt for isolation of B. abortus from dogs
(Salem et al., 1974; Prior, 1976). On the other hand, cats
can be experimentally infected with B. canis producing a
transient bacteraemia. Infected cats do not shed brucellae
and they are relatively resistant when challenged by the oral
route (Tolari et al., 1982). DNA amplification of B. abortus
in samples from wild felids kept at a zoo in Brazil was
reported (Almeida et al., 2013). It is worth to mention that
there is little information regarding feline brucellosis available in the literature at all. However, an outbreak of human
brucellosis due to B. suis bv 5 was traced back to a pet cat
in an urban setting (Repina et al., 1993). Isolation of
B. abortus from the bitch and queen indicates the potential
role of dogs and cats in the transmission and spillover of
brucellosis to livestock and humans. Dogs and cats are not
reported to be a major source of brucellosis for humans
and farm animals, but they can play a significant role for
the persistence of infection within a herd. Consequently,
close contact with infected pets or with their secretions is a
risk factor for diseases in livestock and humans. This study
represents, to our knowledge, the first isolation and identification of B. abortus in dogs and cats in Egypt. Furthermore, this is the first report of feline infection with
B. abortus. The bitch and queen in this study may have
been infected by feeding of contaminated meat, aborted
foetuses and/or drinking of contaminated milk.
Most species of genus Brucella spp. are primarily associated with certain hosts. However, interspecies infections
can also occur, particularly when they are kept in close contact. This study also highlights the gaps and drawbacks in
the control and surveillance programmes of brucellosis
which ignore the role of household and stray dogs and cats
in brucellosis control. Our results suggested that B. abortus
can be transferred to dogs and cats from cattle either
directly or indirectly. B. abortus bv 1 is the second predominant Brucella spp. in cattle in Egypt. It can circulate in
both housed or free-ranging dogs and cats representing a
potential reservoir of infection for wildlife. These animals
may also play a role in the spillover of brucellae from wildlife to farm animals. Control measures have to be implemented taking into account not only stray dogs and cats
but also companion animals.
Conclusion
This study is the first to report the isolation and identification of B. abortus bv 1 from dogs in Egypt and from cats
globally. We hypothesize that the bitch and queen served as
intermediate reservoirs. The lack of awareness for the role
of these animals in the infective cycle of cattle brucellosis
may have caused the re-emergence of brucellosis in an
otherwise well-kept dairy farm having biosecurity and biosafety measures in place.
Conflict of interests
This manuscript has not been simultaneously submitted for
publication in another journal and been approved by all
co-authors. The authors declare that they do not have any
conflict of interest.
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