Plague

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A  zoonotic  systemic  bacterial  infection  caused  by  Yersinia  pestis  (plague  bacillus)  usually transmitted to humans by rodent fleas or by handling an infected animal.  There are 3 forms of  plague infection, depending on the route of infection:  

• Bubonic plague is the most common, caused by the bite of an infected flea Y. pestis,  which enters the body at the bite site and travels through the lymphatic system to the  nearest lymph node, replicates itself and causes the lymph node to be inflamed, tense  and painful, turning into open sores with pus. 
• Septicaemic plague occurs when infection spreads through the bloodstream, following untreated bubonic plague causing bleeding, tissue necrosis and shock. 
• Pharyngeal  and/or  Pneumonic plague  is  the  most  virulent  form  and  is  rare.  It  is typically  caused  by  spread  to  the  lungs  from  advanced  bubonic  plague.  Untreated  pneumonic plague can be fatal. 

Human  to  human  transmission  only  occurs  with  the  pneumonic  form  of  plague  by  infectious  droplets. Incubation period is 2 to 6 days and case fatality rate (CFR) may exceed 50-60% in  untreated bubonic plague and is nearly 100% in untreated pneumonic or septicaemic plague.  However, it is usually <1% with appropriate and timely treatment. Currently, plague is one of the  most important reemerging bacterial zoonoses in the world. 

The main risk factor is exposure to infected populations of wild or domesticated rodents and  their fleas in plague endemic areas. 

Case Definition 

Bubonic Plague 

• Suspected case; Any person with a very painful swelling of lymph nodes – buboes and fever (or  history of fever) or at least 3 of the following: headache or chills or generalized or severe asthenia  and consistent epidemiological features, such as exposure to infected animals and/or evidence of  flea bites and/or residence in or travel to a known endemic area within the previous 10 days. 
• Confirmed  case: Any person with suspected case confirmed by isolation of Yersinia pestis from  blood or aspiration of buboes, or specific seroconversion or rapid diagnostic test detecting the Ag F1  in endemic areas 

Pneumonic Plague 

• Suspected  case: Anyone, of any age, with coughs of less than 5 days with one of the following  signs: Striated sputum from blood or dyspnea or chest pain and Fever (or history of fever) or at least  3 of the following: headache or chills or generalized or severe asthenia and Epidemiological context  (contact with suspect or confirmed pneumonic plague case etc). 
• Confirmed case of pneumonic plague: Any suspected case of plague in which Yersinia pestis has  been isolated in culture Or  Suspect  plague  case  with  positive  F1  rapid  diagnostic  test  (RDT)  and  positive  PCR  or  Seroconversion or increase in IgG antibody titre by 4 to 15 days 

Suspicious  death  of  plague:  Anyone  who  died  suddenly  without  apparent  cause  but  with  an  epidemiological link to plague established and without biological sampling 

Probable case of plague: Any suspected case of plague alive or deceased with F1 rapid diagnostic test (RDT) Or Positive PCR alone 

Note: Human plague remains a public health concern in Tanzania despite its quiescence in most foci for years, considering the recurrence nature of the disease. Plague hosts comprises about  50% of all  the animals trapped in West Usambara Mountains in north-eastern Tanzania. 

Clinical Diagnostic Criteria 

• Sudden onset of fever, chills, head and body aches 
• Weakness, vomiting and nausea
• Yersinia pestis is identified by laboratory testing from a sample of pus from a bubo, blood or sputum
• A specific Y. pestis antigen can be detected by different techniques

Note: Differential diagnosis  Bubonic  plague  may  be  confused  with  streptococcal  or  staphylococcal  lymphadenitis, infectious mononucleosis, cat-scratch fever, lymphatic filariasis, tick typhus, tularemia  and other causes of acute lymphadenopathy 

Laboratory Investigation   

• Aspiration after an injection of 1-2 ml of saline through an 18-22 gauge needle. Suitable microbiological  culture  media  (e.g.  brainheart  infusion,  broth,  sheep  blood  agar,  or  MacConkey agar) should be inoculated with a portion of each specimen.  
• Smears should be examined with Wayson or Giemsa stain and with Gram=s stain to show Small gram-negative and/or bipolar-staining coccobacilli 
• Smears should also be submitted for direct fluorescent antibody testing (anti-F1 antibody) 
• Serological testing: anti-F1 antigen titre by agglutination  
• Molecular biological techniques based on PCR and DNA hybridization 

Note: Anti-F1 rapid diagnostic test (RDT) positive alone is not a confirmed case.  Culture and PCR tests  need to done at the appropriate facility. 

Prevention:  

• Inform  people  of  the  presence  of  zoonotic  plague  and  advised  to  take  precautions against flea bites 
• Do not handle animal carcasses and avoid direct contact with infected body fluids and tissues 
• Apply  standard  precautions  when  handling  potentially  infected  patients  and  while collecting specimens 

Vaccination: Not recommended except for high-risk groups (such as laboratory personnel who are  constantly exposed to the risk of contamination, and health care workers). 

Pharmacological Treatment 

A:  streptomycin  (IM) 30  mg/kg/day  (up  to  a  total  of  2  g/day)  in  divided  doses,  to  be continued  for  10  days  of  therapy  or  until  3  days  after  the  temperature  has  returned  to  normal.  

OR   

A: erythromycin (PO) 500 mg (or 12.5 mg/kg) 8 hourly for 14 days 

OR   

A: doxycycline (PO) 200mg 12 hourly for 14 days 

Public Health Control Measures 

• Remove trash, food sources, and rat harborages to control rodent populations 
• Protect against fleas with insect repellent on skin and clothing 
• Conduct environmental flea control in houses, seaports and airports 
• Isolate patients with pneumonic plague with precautions against airborne spread until at least after 48 hours of appropriate antibiotic therapy 
• Always observe the standard infection prevention and control (IPC) measures
• Conduct community education on the disease symptoms and signs, early reporting/seeking of medical care, disease transmission and prevention, application of infection prevention and control for home care setting. 
• Mobilize community to enable rapid case detection and treatment. 
• Provide chemoprophylaxis using tetracycline (PO) 15-30 mg/kg or chloramphenicol (PO) 30 mg/kg daily in 4 divided doses for 1 week after exposure ceases. 
• Ensure adequate collaboration with other sectors such as livestock, agriculture, environmental and sanitation sectors to ensure appropriate interventions are addressed.