🧬 Brucella species mainly infect cattle, swine, goats, sheep, and dogs.
🥛 Most human cases are due to ingestion of unpasteurised milk, cheese, or dairy products (especially from goats or sheep).
⚠️ It is one of the world’s most common zoonoses, sometimes called “Malta fever” or “undulant fever” because of its relapsing fever pattern.
📖 About
- Intracellular Gram-negative coccobacilli (only 4 species pathogenic to humans).
- Zoonosis – transmitted from animals to humans. Human-to-human spread is extremely rare.
- Endemic in Mediterranean, Middle East, Africa, Asia, and Latin America.
🔬 Microbiology
- B. melitensis 🐐 (goats, sheep, camels) → most severe disease.
- B. abortus 🐄 (cattle) → usually milder disease.
- B. suis 🐖 (pigs) → associated with suppurative complications.
- B. canis 🐕 (dogs) → less common, milder illness.
🩺 Clinical Features
- Incubation period: 1–4 weeks.
- Transmission: Infected milk, cheese, yoghurt, butter, uncooked meat, or inhalation in abattoir/lab workers.
- Systemic symptoms: Pyrexia, rigors, drenching sweats 😰, lethargy, headache.
- Musculoskeletal: Arthralgia, myalgia, suppurative arthritis, synovitis, bursitis, spondylitis, osteomyelitis, paravertebral/psoas abscess.
- CNS: Meningitis, stroke, cranial nerve palsy, myelopathy, subarachnoid haemorrhage, radiculopathy.
- Ocular: Uveitis, retinal thrombophlebitis 👁️.
- Cardiac: Myocarditis, endocarditis ❤️ (leading cause of mortality).
- Respiratory: Pneumonitis, lung abscess, hilar adenopathy.
- Abdominal: Splenic abscess/calcification, hepatitis, orchitis, epididymo-orchitis.
- Characteristic pattern: Undulant fever 🌡️ (recurrent fever with sweats, improving then relapsing).
🧪 Investigations
- Blood cultures: Require prolonged incubation (Brucella grows slowly). B. melitensis is the most readily cultured.
- CSF culture: if neurological involvement suspected.
- Serology: Standard agglutination test – diagnostic titre >1:320 or a four-fold rise in titre.
- FBC, LFTs: may show anaemia, leukopenia, raised transaminases.
💊 Management
- Adults (first-line):
Doxycycline 100 mg BD for 6 weeks + IV Gentamicin for 7 days (or Streptomycin IM for 2–3 weeks).
- Bone involvement: Add Rifampicin 600–900 mg OD for 6 weeks.
- Neurobrucellosis: Add Ceftriaxone 2 g IV BD for 4–6 weeks.
- Children: Co-trimoxazole (Trimethoprim/Sulfamethoxazole) + aminoglycoside (Gentamicin or Streptomycin) or Rifampicin.
- Endocarditis: Requires triple therapy (Doxycycline + Rifampicin + Aminoglycoside) and often surgical valve replacement.
⚠️ Key Points
- Relapse is common if treatment is too short ⏳.
- Brucellosis is a notifiable disease in many countries.
- Prevention: pasteurisation of milk, protective measures for abattoir/laboratory workers, vaccination of livestock.
📚 References
