This document discusses brucellosis, a globally important zoonotic bacterial disease. It is caused by Brucella species and transmitted from animals to humans through contact or consumption of infected animal products like unpasteurized milk. In animals it causes reproductive issues like abortion. In humans it causes non-specific flu-like symptoms. Diagnosis involves isolating the bacteria or detecting antibodies. Treatment is difficult due to antibiotic resistance. It has significant public health and economic impacts especially in developing countries where control measures are not well implemented.

1. Accelerating the world's research.
Brucellosis -An Infectious Re-
Emerging Bacterial Zoonosis of
Global Importance
Mahendra Pal
Cite this paper
Get the citation in MLA, APA, or Chicago styles
Downloaded from Academia.edu 
Related papers
Journal of Veterinary Medicine and Research Brucellosis and Its Control through One Health …
gemechu regea
Brucellosis-A Prominent Bacterial Zoonosis and Strategies for Prevention and Control -A Review
DR. SUBHA GANGULY
Public Health and Economic Importance of Bovine Brucellosis: An Overview
Mahendra Pal, Venkataramana Kandi
Download a PDF Pack of the best related papers 

2. International Journal of Livestock Research ISSN 2277-1964 ONLINE www.ijlr.org
Vol 3(1) Jan’13
Page
28
Brucellosis - An Infectious Re-Emerging Bacterial Zoonosis of Global
Importance
Angesom Hadush , Mahendra Pal*
Department of Microbiology, Immunology, Epidemiology and Public Health, College of
Veterinary Medicine and Agriculture, Addis Ababa University,P.O.B.34,Debre Zeit, Ethiopia
*Corresponding author: palmahendra2@gmail.com
Abstract
Brucellosis, a highly infectious, re-emerging bacterial anthropozoonotic disease of global significance, is
important public health and economic point of view. The disease is found worldwide but it is well
controlled in most developed countries. Brucellosis, caused by several species of Brucella, is a sub-acute
or chronic disease which may affect many species of animals. In cattle, sheep, goats, other ruminants and
pigs, the initial phase following infection is often not apparent. The disease in animals causes tremendous
economic losses. The disease is usually transmitted from infected animals to humans through contact with
animals or consumption of their products mostly dairy products made from unpasteurized milk. It is also
an occupational hazard to persons who are engaged in handling of the infected animals and their
products. Laboratory investigation is imperative to confirm an unequivocal diagnosis of brucellosis.
Since humans acquire the infection from animals, it is emphasized to control the disease in animals.
Proper pasteurization of milk and other dairy products and use of protective wears are important safety
measures in those areas where brucellosis is endemic. In recent years, the global epidemiology of the
disease has not altered drastically. New strains of Brucella may emerge and existing types adapt to
changing social and agricultural practices. Hence, further epidemiological studies on the identification of
new strains of the Brucella should be conducted.
Keywords: Animal, Brucellosis, Epidemiology, Public health, Re-emerging zoonosis
Introduction
Brucellosis is an infectious disease of domestic and wild animals with serious zoonotic implication in
humans. The disease is an important public health problem in many parts of the world. Cattle, goats, pigs,
sheep, horses and dogs play an important role in the transmission of brucellosis to man. The disease is
caused by members of the genus Brucella, a facultative and gram negative bacteria. The importance of
this highly contagious disease is due both to its economic impact on the animal industry and to the severe
hazard it represents to human health (Pal and Jain, 1986;Acha and Szyfres, 2003; Cadmus et al., 2006 and
Pal, 2007).
Different Brucella species can infect humans and the most pathogenic and invasive species for human is
Brucella melitensis followed in descending order by Brucella suis, Brucella abortus and Brucella canis. In
places where brucellosis is endemic, humans can be infected through contact with animals or
consumption of their products mostly dairy products made from unpasteurized milk. The disease also is
an occupational hazard to persons engaged in certain professions such as veterinarians, farmers, slaughter
house workers, butchers and laboratory workers. The mode of transmission of the bacteria varies with the

3. International Journal of Livestock Research ISSN 2277-1964 ONLINE www.ijlr.org
Vol 3(1) Jan’13
Page
29
epidemiological area, the animal reservoir and the occupational exposed groups (Seleem et al., 2010).
Brucellosis in human known as "undulant fever", "Mediterranean fever" or "Malta fever", affects people
of all age groups and of both sexes (Pal, 2007).The annual occurrence of human brucellosis in the world
is over 500,000 cases (Donev et al.,2010).
Brucellosis has been an emerging disease since the discovery of Brucella melitensis by Bruce in 1887.
Subsequently, an increasingly complex pattern of strains has emerged with the identification of Brucella
species and, more recently, types infecting marine mammals. Two novel species, B. ceti and B.
pinnipedialis, with the potential for causing human disease have been isolated from marine mammals.
Another novel species, B. microti, has been isolated from wildlife animals, while B. inopinata has been
isolated from a human case (Amato Gauci, 1995).
In recent years the global epidemiology of the disease has not altered drastically. Because each type has
distinctive epidemiologic features, with each new type, the complexity of the interaction with humans has
increased. New strains may emerge and existing types adapt to changing social and agricultural practices
(Pappas et al., 2006).
Etiology
Brucellosis is caused by a Gram negative, facultative intracellular, coccobacillus or short rod in the family
Brucellaceae. Six major species have been classically characterized: Brucella abortus, Brucella melitensis,
Brucella suis, Brucella canis, Brucella ovis, and Brucella neotomae (Pal, 2007). Brucella species have a
strong host preference. For B. abortus, the host preference is cattle; for B. melitensis, sheep and goats; for
B. suis, swine; for B. canis, dogs; for B. ovis, sheep; and for B. neotomae, rodents (desert rat). Marine
mammal isolates are B. maris for all strains, or B. pinnipediae for strains from pinnipeds (seals, sea lions
and walruses) and B. cetaceae for isolates from cetaceans such as whales, porpoises and dolphins (Refai,
2002).
Transmission
Brucella organisms are present in the reproductive tissues and products of parturition at extremely high
concentrations.The organisms also concentrate in the udders of animals that produce milk used for human
consumption. Brucella organisms can be transmitted to humans through direct contact with infected tissue
via breaks in skin, ingestion of contaminated tissues or milk products, and inhalation or mucosal exposure
to aerosolized bacteria. Other routes, including in utero transmission, person-to-person transmission,
(Poulou et al., 2006), and tissue transplantation–associated transmission, (Kotton, 2007) have been
identified or suggested but are much less common. Among nonhuman animals, the predominant route of
exposure for smooth strains of Brucella is through ingestion or inhalation of organisms that are present in
fetal fluids or other birth products. Herds are typically exposed following the introduction of an infected

4. International Journal of Livestock Research ISSN 2277-1964 ONLINE www.ijlr.org
Vol 3(1) Jan’13
Page
30
animal that subsequently gives birth or aborts a fetus, whereupon pasture or water becomes contaminated
by these excretions
Pathogenesis
Brucella species are facultative intracellular pathogens and establish infection by invading macrophages
and evading macrophage-induced host protection mechanisms (Adams, 2002). These characteristics
contribute to clinical signs and therapeutic considerations, including the difficulty in both diagnosis and
treatment. Following exposure in humans, the organisms travel along the lymphatic pathways; focal
disease is most commonly identified in the reticulo-endothelial tissues such as the liver and spleen. In
chronic infections, organisms typically localize in joints, especially large joints such as the sacroiliac or
lumbar vertebral joints. Pulmonary disease is a less common form of brucellosis (Young, 1995).
Clinical spectrum
Man
Brucellosis is frequently an insidious disease, and initial signs are generally nonspecific, regardless of
species infected. In humans, the incubation period for brucellosis is typically 2 to 3 weeks, but can vary
from 5 days to more than 5 months. Acute infection can be unrecognized and can result in chronic
infection with symptoms recurring years later. Most common symptoms include cyclically recurring
(undulant) fever, night sweats, and neuropsychiatric symptoms such as headache. Common symptoms
also include malaise, sleeplessness, and arthralgias (Pal, 2007). Specific clinical signs are less common
than systemic signs: arthritis, organ involvement, and genitourinary signs develop, generally in that order
of frequency. Spontaneous abortions can occur among pregnant women (Khan et al., 2001).
Animals
Brucellosis is a sub-acute or chronic disease which may affect many species of animals. In cattle, sheep,
goats, other ruminants and pigs the initial phase following infection is often not apparent. In sexually
mature animals, the infection localizes in the reproductive system and typically produces placentitis
followed by abortion in the pregnant female, usually during the last third stage of pregnancy, and
epididymitis and orchitis in the male (Pal,2007). Clinical signs are not pathognomonic and diagnosis is
dependent upon demonstration of the presence of Brucella species either by isolation of the bacteria or
detection of their antigens or genetic material, or by demonstration of specific antibody or cell-mediated
immune responses (Neilson and Duncan, 1990).
Epidemiology
Brucellosis is found worldwide but it is well controlled in most developed countries. Clinical disease is
still common in the Middle East, Asia, Africa, South and Central America, the Mediterranean Basin and
the Caribbean. Brucella species vary in their geographic distribution. B. abortus is found worldwide in

5. International Journal of Livestock Research ISSN 2277-1964 ONLINE www.ijlr.org
Vol 3(1) Jan’13
Page
31
cattle-raising regions except in Japan, Canada, some European countries, Australia, New Zealand and
Israel, where it has been eradicated. Eradication from domesticated herds is nearly complete in the USA.
B. abortus persists in wildlife hosts in some regions, including the Greater Yellowstone Area of North
America. B. melitensis is particularly common in the Mediterranean. It also occurs in the Middle East and
Central Asia, around the Arabian Gulf and in some countries of Central America. This organism has been
reported from Africa and India, but it does not seem to be endemic in northern Europe, North America
(except Mexico), Southeast Asia, Australia or New Zealand. (CFSPH, 2007).
Diagnostic Techniques
The clinical signs are not pathognomonic for brucellosis, although the herd history may be helpful in
diagnosis. Confirmatory diagnosis of Brucella infections can be made only by the isolation and
identification of Brucella, but in situations where bacteriological examination is not practicable, diagnosis
must be based on serological methods. There is no single serological test by which a bacterium can be
identified as Brucella. A combination of growth characteristics, serological, bacteriological and/or
molecular methods should be practiced (Pal, 2007 and OIE, 2009).
The serological tests include Rose Bengal Plate Test (RBPT), Complement Fixation Test (CFT), Serum
Agglutination Test (SAT), Milk Ring Test (MRT), Enzyme Linked Immunosorbent Assay (ELISA) and
Skin-Delayed-Type-Hypersensitivity (SDTH) test (Pal, 2007and OIE, 2009).
The most valuable samples include aborted fetuses (stomach contents, spleen and lung), fetal membranes,
vaginal secretions (swabs), milk, semen and arthritis or hygroma fluids. From animal carcasses, the
preferred tissues for culture are those of the reticulo-endothelial system (i.e. head, mammary and genital
lymph nodes and spleen), the late pregnant or early post parturient uterus, and the udder (OIE, 2009).
A wide range of commercial dehydrated basal media is available, e.g. Brucella medium base, tryptose (or
trypticase) soy agar (TSA). The addition of 2–5% bovine or equine serum is necessary for the growth of
strains such as B. abortus biovar 2. A nonselective, biphasic medium, known as Castaneda’s medium, is
recommended for the isolation of Brucella from blood and other body fluids or milk, where enrichment
culture is usually advised (OIE, 2009).
Identification of Brucella organisms can be carried out by a combination of the following tests: organism
morphology after Gram or Stamp’s staining, colonial morphology, growth characteristics, urease, oxidase
and catalase tests, and the slide agglutination test with an anti-Brucella polyclonal serum (Alton, 1990).
The PCR, including the real-time format, provides an additional means of detection and identification of
Brucella species. Despite the high degree of DNA homology within the genus Brucella, several molecular
methods, including PCR, PCR restriction fragment length polymorphism (RFLP) and Southern blot, have
been developed that allow, to a certain extent, differentiation between Brucella species and some of their

6. International Journal of Livestock Research ISSN 2277-1964 ONLINE www.ijlr.org
Vol 3(1) Jan’13
Page
32
biovars. Pulse-field gel electrophoresis has been developed that allows the differentiation of several
Brucella species (Jensen et al., 1999). Brucella biotyping and distinguishing vaccine strains by PCR can
be accomplished satisfactorily but there has been limited validation of the PCR for primary diagnosis
(OIE, 2009).
The first species-specific multiplex PCR assay for the differentiation of Brucella was described by
Bricker and Halling (Bricker and Halling, 2004). The major advantage of this assay over previously
described PCRs is that it can identify and differentiate in a single step most Brucella species as well as the
vaccine strains (OIE, 2009).
Treatment
As a general rule, treatment of Brucella infected animal is not recommended because of the high
treatment failure rate, cost, and potential problems related to maintaining infected animals in the ongoing
eradication program. As a result treatment is unlikely to be undertaken in animals and no economically
feasible drugs. However, a dose of 100mg of broad long acting tetracycline given every 3 days for a
period of 6 weeks achieved to cure 75% of cases. Other recent drugs such as rifampcin (600-900 mg),
doxycycline 200 mg daily for minimum of 6 weeks for acute brucellosis in adults and intramuscular
streptomycin can be tried (Pal, 2007). A combination of Quinolones and rifampcin also have given good
results (Radostits et al., 2000).
Public Health implications
Brucellosis is one of the major anthropozoonosis of public health importance worldwide (Pal and Jain,
1986). The disease is usually transmitted from infected animals to human by direct contact or by
consumption of raw milk infected with Brucella organisms. Brucellosis is primarily a disease of animals
and is transmitted directly and indirectly to humans. Dairy workers, shepherds, butuches, veterinarians,
abattoir workers and animal husbandry personnel are particularly at risk of acquiring brucellosis (Pal and
Jain, 1986). It constitutes an uncontrolled public health problem in many developing countries (Young,
1995).
Economic significance
Brucellosis causes loses of money in terms of production loss due to infection in animals, preventive
programs and human disease. The common sequel of infertility increase the period between lactations,
and in an infected herd or flock the average inter-calving may be prolonged for several months. In
addition to the loss of milk production, there is loss of calves and interference with the breeding program
(Bernues et al., 1997).
Bioterrorism
Brucella suis was among the earliest agents investigated and developed as a bioterrorism weapon in the
United States offensive bioterrorism program in the 1950s. The zoonotic pathogens B. abortus, B.

7. International Journal of Livestock Research ISSN 2277-1964 ONLINE www.ijlr.org
Vol 3(1) Jan’13
Page
33
melitensis, and B. suis have been identified as Category B bioterrorism agents because they are easily
capable of causing considerable morbidity and low numbers of deaths if used in a mass event (Rotz et al.,
2002).
Prevention and control
Approaches used to control brucellosis are immunization, test and slaughter of confirmed animals
(Dwight, 1999). Vaccination reduces the number of infected animals and permits disease control
(Radostits et al., 2000). Human brucellosis is usually prevented by controlling the infection in animals.
Pasteurization of dairy products is an important safety measure where this disease is endemic.
Unpasteurized dairy products and raw or undercooked animal products (including bone marrow) should
not be consumed. Good hygiene and protective clothing/equipment are very important in preventing
occupational exposure. Precautions should be taken to avoid contamination of the skin, as well as
inhalation or accidental ingestion of organisms when assisting at a birth, performing a necropsy, or
butchering an animal for consumption (CFSPH, 2007).
Conclusion
Brucellosis is an infectious disease of domestic and wild animals with serious zoonotic implications in
humans. The disease in animals causes tremendous economic losses. Brucellosis is prevalent worldwide
but has been controlled in most developed countries. The disease is usually transmitted from the infected
animals to humans; and it is also an occupational hazard to the livestock handlers. Since brucellosis is
primarily an animal disease, emphasis should be given to control the disease in animal populations by
adopting well organized control strategies to protect the public from the risks of acquiring this zoonosis.
Further studies on the molecular epidemiology of brucellosis which can identify of the new
biotypes/strains of Brucella responsible of disease in humans and animals may be rewarding.
Acknowledgement
We are highly grateful to Professor Dr. Ram Krishan Narayan for reviewing our manuscript.
References
Acha N. P. and Szyfres B. 2003: Zoonoses and communicable disease common to man and animal, 3rd
ed., Pan American Health Organization, Washington, DC. Pp. 40-66.
Adams L. G. 2002: The pathology of brucellosis reflects the outcome of the battle between the host
genome and the Brucella genome. Veterinary Microbiology 90:553–561.
Alton G. 1990: Laboratory Techniques in Brucellosis .World Health Organization, Geneva, Switzerland
Pp. 190-195.
Amato Gauci A. J. 1995: The return of brucellosis. Malta Medical Journal 7:7-8.
Bernues A., Manrique E. and Mazam T. 1997: Economic evaluation of bovine brucellosis and
tuberculosis programs in mountain areas of Spain. Preventive Veterinary Medicine 30: 137-149.

8. International Journal of Livestock Research ISSN 2277-1964 ONLINE www.ijlr.org
Vol 3(1) Jan’13
Page
34
Bricker J. and Halling M. 2004: Differentiation of Brucella abortus bv. 1, 2, and 4, Brucella melitensis,
Brucella ovis, and Brucella suis bv. 1 by PCR. Journal of Clinical Microbiology 32: 2660–2666.
Cadmus S. I. B., Ijagbone I. F., Oputa H. E., Adesokan H. K. and Stack J. A.2006: Serological survey of
brucellosis in livestock animals and workers in Ibadan, Nigeria. African Journal of Biomedical Research
9: 163-168.
CFSPH. 2007: Brucellosis in human. Center for Food Security and Public Health, College of Veterinary
Medicine, Iowa State University, Ames, Iowa. Pp. 1-13.
Donev,D., Karadzovski, Z., Kasapinov,B. and Lazarevik,V.2010: Epidemiological and public health
aspects of brucellosis in the Republic of Mecedonia. Biological Medical Science1:33-54.
Dwight H. 1999: Brucella: Bacteriology. Veterinary Microbiology, 1st
ed. Blackwell Science Ltd,
Blackwell Publishing Company. Pp. 196-203.
Jensen E., Cheville F., Thoen O., Macmillan P. and Miller G. 1999: Genomic fingerprinting and
development of a dendrogram for Brucella species isolated from seals, porpoises, and dolphins. Journal
of Veterinary Diagnostic Investigation 11: 152–157.
Khan M. Y., Mah M. W. and Memish Z. A. 2001: Brucellosis in pregnant women. Clinical Infectious
Diseases 32:1172–1177.
Kotton C. N.2007: Zoonoses in solid-organ and hematopoietic stem cell transplant recipients. Clinical
Infectious Diseases 44:857–866.
Nielsen K. and Duncan J. R. 1990: Animal brucellosis. CRC Press, Boca Raton.
OIE 2009: Bovine brucellosis: Terrestrial Manual, Chapter 2.4.3. Version adopted by the World
Assembly of Delegates of the OIE in May, Pp. 1-35.
Pal M. 2007: Zoonoses. 2nd
ed. Satyan Publishers, Jaipur, India. Pp. 98-99.
Pal M. and Jain H. S. 1986: Anthropozoonotic role of Brucella abortus. International Journal of
Zoonoses 13:246-248.
Pappas G., Panagopoulou P. and Christou L.2006: Brucella as a biological weapon. Cellular Molecular
Life Science 63:2229–2236.
Poulou A., Markou F. and Xipolitos I. 2006: A rare case of Brucella melitensis infection in an obstetrician
during the delivery of a transplacentally infected infant. Journal of Infection 53:39–41.
Radostits D., Gay C. and Inchcliff W. 2000: Veterinary Medicine. Textbook of the diseases of cattle,
sheep, pigs, goats and horses. 9th
ed, W.B. Saunders Company Ltd. New York., Pp. 867-882.
Refai M. 2002: Incidence and control of brucellosis in the near east region. Veterinary Microbiology
90:81–110.
Rotz L. D., Khan A. S. and Lillibridge S. R. 2002: Public health assessment of potential biological
terrorism agents. Emerging Infectious Disease 8:225–230.
Seleem M. N., Boyle S. M. and Sriranganathan N.2010: Brucellosis: A re- emerging zoonosis. Veterinary
Microbiology 140: 392-398.
Young E .J. 1995: An overview of human brucellosis. Clinical Infectious Disease 21:283–289.