Disease description

Plague caused by Yersinia pestis, is primarily a disease of rodents and their fleas, which can infect humans. It is a severe disease in people with case fatality rates of 50-60% if left untreated. Plague has been responsible for widespread pandemics with high mortality in the pre-antibiotic era. It was known as the "Black Death" during the fourteenth century, causing an estimated 50 million deaths.

There are three main forms of plague in human.

• Bubonic plague: is the result of an insect bite in which the plague bacillus, Yersenia pestis travels through the lymphatic system to the nearest lymph node where it form a swelling. Commonly presents with acute and fulminant onset of non-specific symptoms including fever, malaise, headache, myalgias, nausea, vomiting and abdominal pain. After which the bubo develops. The bubonic form may progress to septicaemic and or pneumonic forrn.
   
• Septicaemic form: bacteremia is common in patients with bubonic plague. About a quarter of bubonic plague patients progress to clinical septicaemia. This may produce thrombosis, necrosis, gangrene and DIVC.
   
• Penumonic plague: an infection of the lung due to either inhalation (primary pneumonic plague) of the organism or spread to the lung frorn seoticaemia. Prirnary pneumonic plague has an acute and fulminant onset of non-specific symptoms followed within 24 hours by a cough with bloody sputum. The pneumonia progress rapidly resulting in dyspnea, stridor and cyanosis. Without treatment, the disease terminates with respiratory failure and circulatory collapse. Pneumonic plague is highly contagious.
   

Incubation:

• Incubation of bubonic form is 2-10 days.
   
• Primary pneumonic is 1-6 days (average 2-4 days)
   

Laboratory investigations

• Sputum for gram stain and culture.
   
• Lymph node aspiration, blood, or cerebrospinal fluid samples for culture.
   

Medical management:

Empirical treatment should begin when clinically suspected of pneumonic plague as the disease is almost always fatal if treatment is not initiated within 24 hours of the onset of symptoms.

• gentamicin 5mg/kg IM or IV once a day
   
• streptomycin 30mg/kg IM once a day
   
• doxycycline 200mg followed by 100mg bid.
   
• Chloramphenicol 25mg/kg IV loading dose followed by 15mg/kg IV qid is required for the treatment of plague meningitis.

Total duration of treatment is 10-14 days
 

Chemoprophylaxis

Face to face contact (within 2 meters) of patients with pneumonic plague or persons possibly exposed to a plague aerosol should be given antibiotic prophylaxis.

• doxycycline 100mg bid orally
• ciprofloxacine 500mg bid orally
• tetracycline 250mg qid orally
• chloramphenicol 25mg/kg qid orally

• Give chemoprophylaxis for 7 days or the duration of risk of exposure plus 7 days
   
• Contact of bubonic plague patients need only be observed for symptoms for a week. If symptoms occur, start treatment antibiotics.
   
• No vaccine is currently available for prophylaxis against pneumonic plague.
   

Isolation:

Suspected pneurnonic plague cases require strict isolation with droplet precautions for at least 48 hours of antibiotic therapy or until sputum cultures are negative in confirmed cases.


Case fatality:

• Untreated bubonic plague is approximately 60%.
   
• Untreated pneumonic plague is nearly 100%. Survival is unlikely if treatment is delayed beyond 18 hours of infection.