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Brucellosis
A zoonosis
Brucella spp.
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Gram negative, coccobacilli bacteria
Facultative, intracellular organism
Multiple species
Center for Food Security and Public Health
Iowa State University - 2004
Species
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Brucella melitensis: most common
B. abortus
B. suis
B. canis
Center for Food Security and Public Health
Iowa State University - 2004
Transmission to Humans
1) Conjunctiva or broken skin
contacting infected tissues:
− Blood,
urine, vaginal discharges,
aborted fetuses, placentas
2) Ingestion:
− Raw
milk & unpasteurized dairy
products
− Rarely through undercooked meat
Center for Food Security and Public Health
Iowa State University - 2004
Transmission to Humans
3) Inhalation of infectious aerosols:
− Pens,
stables, slaughter houses
4) Inoculation with vaccines
5) Person-to-person (sexual, congenital,
breast-feeding) is rare
• Incubation varies
− 7-21
days to several months
Center for Food Security and Public Health
Iowa State University - 2004
Who is at Risk?
1) Occupational Disease
− Cattle
ranchers/ dairy farmers
− Veterinarians
− Abattoir workers
− Meat inspectors
− Lab workers
2) Hunters
3) Travelers
Center for Food Security and Public Health
Iowa State University - 2004
4) Consumers of
unpasteurized
dairy products
Center for Food Security and Public Health
Iowa State University - 2004
B. melitensis
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B melitensis is thought to be
the most virulent and causes
the most severe and acute
cases of brucellosis; it is also
the most prevalent worldwide.
Center for Food Security and Public Health
Iowa State University - 2004
Human Disease
• Flu-like illness is the most common
presentation ( 80-100%). Fever is
intermittent in 60% of patients with acute
and chronic disease. Fever can be
associated with a relative bradycardia.
Constitutional symptoms include anorexia,
asthenia, fatigue, malaise, and wt loss.
• Hepatosplenomegaly and
lymphadenopathy (30%)
Center for Food Security and Public Health
Iowa State University - 2004
Human Disease
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Localized infection may be the
presenting feature:
Osteoarticular complications
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Arthritis, spondylitis, osteomyelitis
Genitourinary involvement:
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Orchitis and epididymitis most common
Center for Food Security and Public Health
Iowa State University - 2004
Human Disease
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Neurological:
− Depression,
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meningitis
Cardiovascular:
− Endocarditis
resulting in death
Center for Food Security and Public Health
Iowa State University - 2004
Chronic brucellosis
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The diagnosis of chronic brucellosis is
typically made after symptoms have
persisted for 1 year or more. Lowgrade fevers and neuropsychiatric
symptoms predominate. Results of
serologic studies and cultures are
often negative
Center for Food Security and Public Health
Iowa State University - 2004
Diagnosis in Humans
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Culture of:
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Blood, bone marrow, CSF, urine (50% +ve)
Subcultures are still advised for at least 4 weeks
BM culture has higher yield. Sensitivity is usually 8090%
Serum agglutination test
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Fourfold or greater rise in titer
Samples 2 weeks apart
The 2-mercaptoethanol test detects IgG, and titers
higher than 1:160 define active infection. A high IgG
titer or a titer that is higher after treatment suggests
persistent infection or relapse. IgM Ab indicate recent
infection.
Center for Food Security and Public Health
Iowa State University - 2004
Serology
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ELISA typically uses the cytoplasmic
proteins as antigens and measures
IgM, IgG, and IgA, allowing better
interpretation, especially in cases of
relapse
Center for Food Security and Public Health
Iowa State University - 2004
Treatment of Choice
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Combination therapy
− Doxycycline
100mg bd for 6 weeks +
streptomycin 1g/d im for 2 wk or
rifampicin 600mg/d for 6 wk
− In pregnancy: rifadin+ co-trimoxazole
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CNS cases treat 6-9 months
− Same
for endocarditis cases plus
surgical replacement of valves
Center for Food Security and Public Health
Iowa State University - 2004
Prognosis
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May last days, months or years
Recovery is common
Disability is often pronounced
About 10% of treated cases relapse
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Failure to complete the treatment regimen
Sequestered infection requiring surgical
drainage
Case-fatality rate: <2% usually from
endocarditis
Center for Food Security and Public Health
Iowa State University - 2004
Prevention and Control
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Education about risk of transmission
− Farmer,
veterinarian, abattoir worker,
butcher, consumer, hunter, public
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Wear proper attire if dealing with
infected animals/ tissues
− Gloves,
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masks, goggles
Avoid consumption of raw dairy
products
Center for Food Security and Public Health
Iowa State University - 2004
Prevention and Control
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Immunize in areas of
high prevalence
− Young
goats and sheep
− Calves
− No
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human vaccine
Eradicate reservoir
− Identify,
segregate, or cull
infected animals
Center for Food Security and Public Health
Iowa State University - 2004