Brucellosis is a bacterial zoonotic infection caused by Brucella species — transmitted from infected animals (cattle, goats, sheep, pigs, camels, dogs) to humans through unpasteurised dairy products, direct contact with infected animals, or inhalation of aerosols. It is the world's most widespread zoonotic disease by case numbers — causing approximately 500,000 cases per year globally, with massive underreporting making the true burden much higher.

How is brucellosis transmitted?

The primary transmission route globally is consumption of unpasteurised dairy products — raw milk, fresh cheese (particularly soft cheeses), yogurt and ice cream from infected animals. Direct contact with infected animals (cattle, goats, sheep) is the main occupational route — particularly for farmers, shepherds, abattoir workers and veterinarians. Transmission through handling infected animal products (placenta, aborted fetuses) is highly efficient. Human-to-human transmission is extremely rare.

What are the symptoms?

Brucellosis causes an insidious febrile illness: fever (typically low-grade, with characteristic diurnal variation — higher in evenings); profuse night sweats; arthralgia and myalgia; fatigue; headache; and malaise. Localised complications: osteoarticular (most common — sacroiliitis, spondylitis, peripheral arthritis); neurobrucellosis (meningitis, encephalitis); endocarditis (rare, most lethal); epididymo-orchitis (in men); and hepatosplenomegaly.

Why is brucellosis so often missed?

Brucellosis is called "the great imitator" — its non-specific presentation mimics malaria, typhoid, visceral leishmaniasis, influenza and rheumatological conditions. Most clinicians in endemic areas don't consider brucellosis in the differential or don't have access to diagnostic tests (SAT, ELISA). Positive test results require expertise to interpret. In many endemic countries, clinicians prescribe empirical antimalarials or antibiotics without confirming the diagnosis, allowing brucellosis to progress to chronic disease.

How is brucellosis treated?

WHO recommends combination antibiotic therapy for minimum 6 weeks: doxycycline (100mg twice daily) + rifampicin (600-900mg/day) for 6 weeks (standard regimen); OR doxycycline for 6 weeks + gentamicin IV for 7 days (alternative — slightly lower relapse rate). Monotherapy is NOT acceptable — leads to 30-40% relapse rates. Complicated brucellosis (neurobrucellosis, endocarditis, osteomyelitis) requires prolonged courses (3-6+ months) and specialist management.

How is brucellosis prevented?

The most impactful human prevention measure: pasteurisation of all dairy products (eliminates the primary transmission route). Animal vaccination programmes (Rev-1 for sheep/goats, RB51 for cattle) reduce the animal reservoir. Occupational measures: personal protective equipment for farmers, veterinarians and abattoir workers; safe handling of animal birthing products. Countries that have sustained comprehensive animal vaccination and dairy pasteurisation programmes have eliminated human brucellosis (UK, Australia, US).

Is brucellosis endemic in Georgia?

Yes — Georgia and the South Caucasus are in the brucellosis-endemic belt. Livestock (particularly sheep, goats and cattle) serve as the reservoir. Transmission routes: raw milk consumption; traditional unaged soft cheeses (popular in Georgian cuisine); and farming communities with close animal contact. Georgia's PHIG and veterinary authorities have implemented brucellosis control programmes. The GMJ has published research on brucellosis epidemiology in the South Caucasus.

What is neurobrucellosis?

Neurobrucellosis — CNS involvement in brucellosis — occurs in approximately 1-2% of cases but carries high morbidity. Manifestations: meningitis (most common); meningoencephalitis; myelitis; peripheral neuropathy; and — rarely — stroke (from vasculitis). Diagnosis: CSF culture and serology. Treatment: prolonged (3-6 month) triple combination (doxycycline + rifampicin + TMP-SMX) ± ceftriaxone for severe disease.

What is the link between brucellosis and abortion in animals?

In animals, Brucella infection causes reproductive failure — spontaneous abortion, stillbirth and infertility. In cattle, B. abortus causes "contagious abortion." The aborted fetus, placenta and uterine discharges are massively infectious — contaminating the environment and posing direct human exposure risk to farmers and veterinarians. This is why animal vaccination and safe disposal of aborted material are critical One Health interventions.

Is there a human brucellosis vaccine?

No approved human vaccine for brucellosis exists. Animal vaccines (Rev-1, RB51) cannot be used in humans due to virulence. Several human vaccine candidates are in early development — including subunit vaccines targeting Brucella outer membrane proteins. Prevention in humans relies entirely on animal reservoir control and food safety measures (pasteurisation).

How does GMJ News cover brucellosis?

GMJ News covers WHO brucellosis data, Georgia and South Caucasus epidemiology, animal vaccination programmes, dairy safety and One Health prevention approaches. Brucellosis is a direct public health concern for Georgia — relevant to PHIG's One Health mandate and the Georgian Medical Journal's clinical and epidemiological coverage.

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Brucellosis

GMJ News knowledge hub · last reviewed September 2026 · Georgian Medical Journal

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Brucellosis — caused by Brucella bacteria transmitted from infected animals (cattle, sheep, goats, pigs, dogs) to humans — affects an estimated 500,000 people per year and is considered the world's most widespread zoonotic disease in terms of incidence, with true burden possibly 10-25 times higher due to severe underreporting in endemic regions (WHO). Brucellosis causes a highly non-specific febrile illness — fever, arthralgia, night sweats, fatigue — that mimics malaria, typhoid and influenza, making it one of the most commonly misdiagnosed infectious diseases. Endemic across the Mediterranean, Middle East, Central Asia, Sub-Saharan Africa and Latin America, brucellosis is controlled in livestock-raising communities through animal vaccination programmes and prevention of unpasteurised dairy consumption.

Key messages

500,000 cases per year

Brucellosis affects an estimated 500,000 people per year globally — the world's most widespread zoonotic disease by incidence, though 10-25 times more cases are estimated to occur than are officially reported (WHO).

Zoonotic — from infected animals

Brucellosis is transmitted from infected cattle, goats, sheep, pigs, camels and dogs to humans through: consumption of unpasteurised dairy products (primary route globally); direct contact with infected animals or their secretions; and — rarely — laboratory exposure or inhalation.

Non-specific presentation

Brucellosis causes a "great mimicker" febrile illness — fever, night sweats, arthralgia, fatigue, malaise — virtually indistinguishable clinically from malaria, typhoid, visceral leishmaniasis and influenza. This non-specificity leads to systematic misdiagnosis.

Highly treatable

Brucellosis is effectively treated with a 6-week course of doxycycline + rifampicin (or doxycycline + gentamicin for the first 7 days). Relapse rates with appropriate treatment are approximately 5-10%. A full 6-week course is essential to prevent relapse.

Animal vaccination is the real solution

Human brucellosis is eliminated by controlling brucellosis in animals — through vaccination of cattle and small ruminants (Rev-1 for sheep/goats, S19/RB51 for cattle) and proper pasteurisation of dairy products. Countries with effective animal vaccination have eliminated human brucellosis.

Endemic in Mediterranean and Middle East

Brucellosis is most prevalent across the Mediterranean basin, Middle East, Central Asia, South America and Sub-Saharan Africa. Georgia and the South Caucasus are in an endemic zone — directly relevant to PHIG's One Health programme.

Key statistics

500K

estimated cases/year

WHO

10-25x

estimated underreporting factor

WHO/research

170+

countries reporting brucellosis

WHO/OIE

5-10%

relapse rate with correct treatment

WHO/IDSA

6 weeks

minimum antibiotic treatment duration

WHO

~2%

case fatality rate (untreated disease)

WHO

Estimated brucellosis cases per year by region (thousands) — WHO/OIE

Source: WHO. Mediterranean, Middle East and Central Asia most affected. True burden vastly underestimated.

Glossary of key terms

Brucella species
WHO/OIEFour main species cause human disease: B. melitensis (from sheep/goats — most pathogenic); B. abortus (cattle — moderate pathogenicity); B. suis (pigs — highly pathogenic); B. canis (dogs — mild disease). B. melitensis causes the vast majority of human cases globally.

Brucellosis diagnostic tests
WHOSerology: Rose Bengal Test (rapid screening, cheap); Standard Agglutination Test (SAT — titre ≥1:160 diagnostic); Brucella IgM/IgG ELISA. Culture: blood culture (gold standard, positive in ~50-70% of acute cases — requires 7-14 days incubation). PCR: increasingly used in specialised centres.

Undulant fever
WHO/HistoryThe historical name for brucellosis — reflecting the characteristic undulating (waves of) fever, with temperatures rising in the evening and normal in the morning. Also called Malta fever (first described in Malta by David Bruce in 1887) and Mediterranean fever.

Doxycycline + rifampicin
WHO/IDSAThe WHO-recommended treatment for uncomplicated brucellosis — doxycycline 100mg twice daily for 6 weeks PLUS rifampicin 600-900mg/day for 6 weeks. Both drugs required together — monotherapy leads to high relapse rates.

Chronic brucellosis
WHO/ClinicalPersistent Brucella infection (>1 year symptoms) — causing fatigue, musculoskeletal pain, depression and cognitive difficulties. Controversial entity — may represent ongoing infection, immune dysregulation or post-infectious syndrome. Requires prolonged antibiotic courses.

Rev-1 vaccine
WHO/OIEThe Brucella melitensis Rev-1 live attenuated vaccine — used for vaccination of sheep and goats. Highly effective but cannot be used in cattle and requires careful handling (biohazard risk). Core of national brucellosis control programmes in endemic countries.

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Brucellosis

Key messages

Key statistics

Glossary of key terms

Latest GMJ coverage

Frequently asked questions 12 Q&A — structured for Google featured snippets and AI discovery

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