Undulant Fever — Brucellosis

Undulant fever, medically known as brucellosis, is a zoonotic infectious disease caused by the bacteria Brucella. The disease affects both humans and animals, with transmission often occurring through direct contact with infected animals or consumption of contaminated animal products. Brucellosis derives its name from the characteristic wave-like fever pattern seen in infected individuals. It is a significant public health and economic concern, particularly in regions where animal husbandry is a major industry. This article provides a comprehensive overview of brucellosis, including its causes, symptoms, diagnosis, treatment, prevention, and global impact.

What is Brucellosis?

Overview

Brucellosis is a bacterial infection caused by various species of Brucella, which primarily affect domestic and wild animals but can also infect humans. It is often referred to as undulant fever due to the periodic rise and fall of fever in humans.

Brucella Species and Hosts

• Humans:
  • Brucella melitensis: Most virulent species, commonly found in goats and sheep.
  • Brucella abortus: Found in cattle.
  • Brucella suis: Found in pigs.
  • Brucella canis: Found in dogs.
• Animals:
  • Includes cattle, goats, sheep, pigs, dogs, and wildlife such as deer and bison.

Causes and Transmission

Modes of Transmission

1. Direct Contact:
   • Handling infected animals or their tissues (e.g., during slaughter or veterinary procedures).
2. Ingestion:
   • Consumption of unpasteurized dairy products, such as milk, cheese, or ice cream.
3. Inhalation:
   • Breathing in aerosolized particles from animal secretions, particularly in laboratory or abattoir settings.
4. Human-to-Human Transmission:
   • Extremely rare but can occur through blood transfusion, organ transplantation, or breastfeeding.

Risk Factors

• Occupations involving animal handling (e.g., farmers, veterinarians, butchers).
• Consumption of raw or unpasteurized dairy products.
• Travel to endemic regions.
• Laboratory personnel working with Brucella cultures.

Symptoms of Brucellosis

Incubation Period

• Typically ranges from 5 days to several months, with most cases appearing within 2-4 weeks after exposure.

Acute Symptoms

1. Fever:
   • Undulating pattern of high and low fever.
2. Sweats:
   • Often profuse and nocturnal.
3. Fatigue:
   • Debilitating tiredness.
4. Muscle and Joint Pain:
   • Particularly in large joints such as the knees and hips.
5. Headache and Malaise:
   • General feeling of discomfort and weakness.

Chronic Symptoms

1. Arthritis:
   • Chronic joint inflammation.
2. Neurological Symptoms:
   • Depression, memory issues, or peripheral neuropathy.
3. Recurrent Fever:
   • Periodic episodes of fever over months or years.
4. Organ Involvement:
   • Hepatosplenomegaly (enlarged liver and spleen), endocarditis, or orchitis (inflammation of the testicles).

Complications of Brucellosis

Severe Cases

• Endocarditis:
  • Infection of the heart valves, a leading cause of brucellosis-related mortality.
• Neurobrucellosis:
  • Involvement of the central nervous system, leading to meningitis or encephalitis.
• Osteoarticular Involvement:
  • Chronic arthritis, sacroiliitis (inflammation of the sacroiliac joint), or spondylitis (spinal inflammation).
• Reproductive Issues:
  • Miscarriage, infertility, or orchitis in males.

Diagnosis

Clinical Diagnosis

• Based on history of exposure to animals or animal products and characteristic symptoms.

Laboratory Tests

1. Serology:
   • Standard agglutination test (SAT) or enzyme-linked immunosorbent assay (ELISA) to detect antibodies against Brucella.
2. Blood Cultures:
   • Gold standard for diagnosis, though sensitivity may decrease in chronic cases.
3. Molecular Tests:
   • Polymerase chain reaction (PCR) for rapid and specific identification of Brucella DNA.
4. Tissue Biopsy:
   • Histopathological examination of affected organs.

Imaging Studies

• X-rays, MRI, or CT scans for complications such as spondylitis or organ involvement.

Treatment

Antibiotic Therapy

• Combination Therapy:
  • Doxycycline (6 weeks) plus streptomycin (2-3 weeks) or rifampin (6 weeks).
• Alternative Regimens:
  • Trimethoprim-sulfamethoxazole (TMP-SMX) for pregnant women or children.

Supportive Care

• Pain management with NSAIDs.
• Physical therapy for joint and muscle rehabilitation.

Treatment of Complications

• Endocarditis may require prolonged antibiotic therapy or surgical intervention.
• Neurobrucellosis often necessitates higher doses and extended duration of antibiotics.

Prevention

Animal Control Measures

1. Vaccination:
   • Vaccinating livestock against Brucella abortus and Brucella melitensis.
2. Testing and Culling:
   • Identifying and removing infected animals.
3. Quarantine Procedures:
   • Isolating imported animals in non-endemic regions.

Food Safety

1. Pasteurization:
   • Ensuring dairy products are pasteurized.
2. Safe Meat Handling:
   • Cooking meat thoroughly to kill bacteria.

Personal Protective Measures

1. Protective Clothing:
   • Gloves, masks, and goggles for individuals handling animals or working in laboratories.
2. Hygiene Practices:
   • Washing hands and disinfecting equipment after animal contact.

Public Health Initiatives

• Education campaigns about the risks of consuming unpasteurized products.
• Strengthening surveillance and reporting systems in endemic areas.

Global Impact of Brucellosis

Economic Burden

• Losses in livestock productivity due to abortions, reduced milk yield, and infertility.
• Healthcare costs for treating human cases and managing complications.

Endemic Regions

1. Middle East and Mediterranean Basin:
   • High prevalence due to traditional livestock practices.
2. Asia and Africa:
   • Limited access to veterinary care and food safety measures.
3. Latin America:
   • Endemic in rural farming communities.

Eradication Challenges

• Resistance to culling infected livestock due to cultural and economic reasons.
• Inadequate funding for vaccination programs and public health infrastructure.

Research and Innovations

Diagnostic Advances

• Development of point-of-care diagnostic tests for use in remote areas.

Vaccine Development

• Efforts to create safer and more effective vaccines for both humans and animals.

Genomic Studies

• Sequencing Brucella genomes to identify virulence factors and drug targets.

Undulant fever or brucellosis remains a complex zoonotic disease with significant health and economic implications. While it is preventable through effective animal control and food safety measures, eradication requires coordinated efforts across veterinary, medical, and public health sectors. Early diagnosis and appropriate treatment are crucial to reducing complications and improving outcomes for affected individuals. Continued research and education will play pivotal roles in combating this ancient yet persistent disease.