Zoonotic Infections: Yersinia, Francisella, Pasturella, and Brucella

Introduction

• Lecture by: Dr. Cabrera
• Topics: Yersinia, Francisella, Pasturella, Brucella
• Focus: Zoonotic infections

Yersinia

• Overview: Cause of the plague, also known as Black Death.
• Transmission: Infected by bites from fleas on wild rodents.
• Identification: Non-motile, facultative, anaerobic, gram-negative rod with bipolar staining.
• Virulent Strains: Produce V and W antigens.
• Incubation Period: 2-7 days.
• Symptoms: High-grade fever, buboes (painful, tender lymphadenopathies), DIC (disseminated intravascular coagulation), hypotension, altered mental status.
• Treatment: Streptomycin; tetracycline as an alternative.
• Endemic Regions: India, SE Asia (Vietnam), Africa, Northern South America
• Vectors: Rat flea (Xenopsylla cheopis)

Other Yersinia Members

• Yersinia enterocolitica: Transmitted through contamination of food, drink, or fomites.
• Yersinia pseudotuberculosis: Transmitted through feces of farm animals and birds.

Prevention and Control

• Avoid contact with animal feces.
• Use protective gear.
• Screen for infected animals, meat, and dairy products.

Francisella tularensis (Tularemia)

• Transmission: Biting arthropods, direct contact with infected animal tissues, inhalation of aerosols, ingestion of contaminated food and water.
• Types of Tularemia:
  • Ulceroglandular: Acquired through skin abrasions; presents with ulcerating papules, regional lymphadenopathies.
  • Pneumonic: Acquired through inhalation; causes peribronchial inflammation and pneumonitis.
  • Oculoglandular: Transmitted to conjunctiva; results in infected lymph nodes.
  • Oropharyngeal: Affects the oropharyngeal area.
  • Typhoidal: Presents as septicemia.
• Diagnosis: Blood serology, culture of lymph node aspirates, bone marrow, blood, tissue biopsies.
• Treatment: Streptomycin or gentamicin for 10 days; tetracycline as an effective alternative.
• Bioterrorism: Classified as a Category A agent.
• Resistance: Resistant to beta-lactam antibiotics.

Pasturella

• Common Species:
  • P. multocida: Found in respiratory tracts of cattle, sheep, swine, horses, fowl.
  • P. pneumotropica: Normal flora in mice and rats; can cause pneumonia or sepsis.
• Human Infection: Typically follows animal bites; symptoms include redness, swelling, pain.
• Treatment: Most antibiotics effective; drug of choice is penicillin G; alternatives include tetracyclines, fluoroquinolones.

Brucella (Brucellosis)

• Species and Hosts:
  • B. abortus: Cattle
  • B. canis: Dogs
  • B. suis: Pigs
  • B. melitensis: Sheep and goats
• Transmission: Direct contact with infected animals; consumption of unpasteurized milk/cheese.
• Symptoms: Intermittent fever, malaise, lasting months if untreated.
• Histologic Reaction: Proliferation of mononuclear cells, fibrin exudation, coagulation necrosis, fibrosis, granulomas.
• Diagnosis: Blood culture, lymph node biopsy, bone culture, serologic testing.
• Treatment: Tetracycline or ampicillin; combination with streptomycin or doxycycline for 2-6 weeks.

Conclusion

• Summary: Overview of zoonotic infections Yersinia, Francisella, Pasturella, and Brucella and their treatments.
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