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Infectious disease and microbiology – Plague
Plague is a severe zoonotic infection caused by Yersinia pestis, a gram-negative aerobic coccobacillus belonging to the Enterobacteriaceae family. Historically, plague caused the devastating “Black Death” pandemics of the Middle Ages. Clinically, the disease may present as bubonic, septicemic, pneumonic, meningeal, or pharyngeal plague.
Plague remains endemic in several regions of the world, especially in parts of Africa, Asia, and the Americas. Between 1998 and 2003, more than 38,000 cases and nearly 3,000 deaths were reported globally. In the United States, most cases occur in the southwestern states, particularly New Mexico, Arizona, and Colorado.
Major risk factors include residence or travel in endemic areas, poor rodent control, exposure to rodents or rodent predators, occupational exposure among veterinarians and laboratory workers, close contact with infected animals, and inadequate flea control in domestic animals.
The disease is maintained in nature through an enzootic cycle involving rodents and fleas. Humans are accidental hosts and do not contribute significantly to maintaining transmission. Infection occurs through:
Clinical Forms
Bubonic plague
The most common presentation.
Symptoms
Septicemic plague
May occur primarily or as progression from bubonic disease.
Features
Pneumonic plague
The most dangerous and contagious form.
Symptoms
Meningeal plague
Rare complication due to CNS seeding during bacteremia.
Features
Diagnosis
Laboratory abnormalities may include:
Special culture media include:
Chest radiography in pneumonic plague may show:
Treatment
First-line therapy
Aminoglycosides
Alternative agents
Supportive Care
Management may also require:
Infection Control
Pneumonic plague
Requires:
Standard precautions are usually sufficient.
Healthcare and laboratory personnel should be informed immediately if plague is suspected because Y. pestis is considered a potential bioterrorism agent owing to its high virulence and aerosol transmissibility.
Prognosis and Complications
Untreated plague has mortality rates approaching 50%, while untreated pneumonic plague is almost universally fatal.
Complications include:
Plague is a severe zoonotic infection caused by Yersinia pestis, a gram-negative aerobic coccobacillus belonging to the Enterobacteriaceae family. Historically, plague caused the devastating “Black Death” pandemics of the Middle Ages. Clinically, the disease may present as bubonic, septicemic, pneumonic, meningeal, or pharyngeal plague.
Plague remains endemic in several regions of the world, especially in parts of Africa, Asia, and the Americas. Between 1998 and 2003, more than 38,000 cases and nearly 3,000 deaths were reported globally. In the United States, most cases occur in the southwestern states, particularly New Mexico, Arizona, and Colorado.
Major risk factors include residence or travel in endemic areas, poor rodent control, exposure to rodents or rodent predators, occupational exposure among veterinarians and laboratory workers, close contact with infected animals, and inadequate flea control in domestic animals.
The disease is maintained in nature through an enzootic cycle involving rodents and fleas. Humans are accidental hosts and do not contribute significantly to maintaining transmission. Infection occurs through:
- Bite of an infected flea
- Direct contact with infected animals or carcasses
- Inhalation of respiratory droplets from pneumonic plague patients or infected animals
Clinical Forms
Bubonic plague
The most common presentation.
Symptoms
- Sudden fever and chills
- Headache and weakness
- Painful swollen lymph nodes (“buboes”) appearing within 24 hours
- Large, tender, erythematous lymph nodes
- Usually inguinal or femoral nodes
- Buboes may ulcerate
- Flea-bite papules or pustules may be present
Septicemic plague
May occur primarily or as progression from bubonic disease.
Features
- Severe sepsis and toxic appearance
- Hypotension
- Gastrointestinal symptoms
- Disseminated intravascular coagulation
- Acral gangrene (“black death”)
- Buboes may be absent
Pneumonic plague
The most dangerous and contagious form.
Symptoms
- Rapidly progressive pneumonia
- Productive cough with bloody sputum
- Pleuritic chest pain
- Severe respiratory distress and hypoxia
Meningeal plague
Rare complication due to CNS seeding during bacteremia.
Features
- Fever
- Headache
- Neck stiffness
Diagnosis
Laboratory abnormalities may include:
- Leukocytosis
- Thrombocytopenia
- Elevated liver enzymes
- Elevated creatinine and BUN
- Disseminated intravascular coagulation in severe disease
- Bubo aspirates
- Sputum
- Throat swabs
- CSF
- Skin swabs
Special culture media include:
- MacConkey agar
- Chocolate agar
- Sheep blood agar
- Brain-heart infusion broth
Chest radiography in pneumonic plague may show:
- Lobar or patchy infiltrates
- Cavitation
- Pleural effusions
- ARDS-like diffuse opacities
Treatment
First-line therapy
Aminoglycosides
- Streptomycin 30 mg/kg/day IM in 2 divided doses
- Gentamicin 2.5 mg/kg IM every 12 hours
Alternative agents
- Doxycycline
- Tetracycline
- Chloramphenicol
- TMP-SMX
Supportive Care
Management may also require:
- Intravenous fluids
- Analgesics and antipyretics
- Intensive care support for septic shock or respiratory failure
Infection Control
Pneumonic plague
Requires:
- Respiratory droplet isolation
- Hospital admission
- Immediate antimicrobial treatment
Standard precautions are usually sufficient.
Healthcare and laboratory personnel should be informed immediately if plague is suspected because Y. pestis is considered a potential bioterrorism agent owing to its high virulence and aerosol transmissibility.
Prognosis and Complications
Untreated plague has mortality rates approaching 50%, while untreated pneumonic plague is almost universally fatal.
Complications include:
- Pneumonia
- Septic shock
- Multiorgan failure
- Respiratory failure
- Disseminated intravascular coagulation
- Secondary bacterial superinfection of buboes
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