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Plague

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31 October 2017

Full revision of guideline

Plague is a Listed Human Disease (LHD) under the Biosecurity Act 2015.

Infectious Agent

The agent is Yersinia pestis, the plague bacillus.

Notification Criteria

Reporting

Only confirmed cases should be notified. Plague must be notified immediately by telephone, followed by written notification within 5 days.

Confirmed case

A confirmed case requires laboratory definitive evidence only. Laboratory results must be confirmed by Forensic Scientific Services.

Laboratory Definitive Evidence

Isolation of Yersinia pestis.

Clinical Evidence

Not applicable.

Community Outbreak Criteria

The World Health Organisation (WHO) requires the first imported, non-imported or transferred case to be reported by electronic means to WHO and adjacent countries. For practical purposes this means one case is considered an outbreak.

Notification Procedure

Pathology laboratories

Pathology laboratories are required to notify the relevant public health unit on receipt of request for examination by telephone and upon confirmation of diagnosis by telephone or facsimile.

The Public Health Unit should immediately notify confirmed or suspected cases to the Chief Human Biosecurity Officer (Executive Director, Communicable Diseases Branch) (confirmed or suspected cases). Plague is subject to the Commonwealth Biosecurity Act 2015.

Data Management

Data entry within 1 working day of notification.

Lab Aspects

Collect blood, and other clinical materials such as bubo aspirates, sputum, tracheal washes, swabs of skin lesions or pharyngeal mucosa, acute and convalescent sera and CSF as indicated (Bennett, 2014).

When a patient’s condition allows, several blood cultures taken over a 45-minute period prior to treatment will increase likelihood of successful isolation of the bacterium (Guerrant, 2011). Airborne precautions should be used for all procedures that could potentially produce aerosols e.g. tracheal washes and aspirates.

If a clinical laboratory isolates an organism with growth features characteristic of this organism, the isolate should be forwarded immediately to Queensland Health Forensic and Scientific Services (FSS) and further work should cease until the identity is confirmed. The FSS must be notified prior to transfer of the culture.

Extensive post-mortem examination is discouraged in cases of suspected plague because of the risk of aerosolising Y. pestis present in body fluids.

Reporting to NOCS

Laboratories to report receipt of request for examination and confirmed cases.

Confirmed Case

A confirmed case requires Laboratory definitive evidence only.

Probable Case

Report only confirmed cases.

Public Health Significance and Occurrence

Plague is an acute, life-threatening zoonosis. It is caused by the bacteria Yersinia pestis, a zoonotic bacterium usually found in small mammals, such as rodents, and their fleas. Humans are “dead-end” hosts. Impoverished populations living under substandard conditions are most at risk.

Plague is transmitted to humans through bites of infected fleas, touching or skinning infected animals, or inhaling infected respiratory droplets/small particles from a patient with pneumonic plague. (Centers for Disease Control and Prevention, 2017; World Health Organisation, 2017). It is highly infectious, and the mortality rate for untreated plague is 30 to 60% for the bubonic type. Untreated primary septicaemic plague and pneumonic plague are almost invariably fatal (World Health Organisation, 2017).

As an animal disease, plague is found in all continents, except for Oceania. Epidemics have occurred in Africa, Asia and South America since the 1990’s. Annually most human cases occur in Africa, with Madagascar considered to be the most highly endemic country. During 2010 – 2015 there were 3,248 cases reported worldwide, including 548 deaths. The 3  most endemic countries globally are Democratic Republic of the Congo, Madagascar and Peru. In Madagascar cases of bubonic plague are reported nearly every year between September and April. In August 2017, an outbreak of pneumonic plague was reported in Madagascar, this unusual and serious event of public health significance is occurring in densely populated cities such as Antananarivo (capital city) and Toamasina (port city) (Public Health England, 2017; World Health Organisation, 2017).

Plague is not present in Australia. The last case of human plague in Australia occurred in the 1920’s.

Medical personnel should be aware of areas where the disease is endemic and consider the diagnosis of plague early, especially in international travellers who develop illness.

Plague is a potential danger as a weapon of bioterrorism. The deliberate release of an aerosol of Y. pestis would be expected to result in an outbreak of respiratory plague with potential for person-to-person spread.

Reservoirs

No enzootic (animal) reservoir for Y. pestis exists in Australia.

In affected counties wild rodents are the natural host of plague. Domestic rats, rabbits, hares and wild carnivores may also become infected and act as a source of infection. Historically in epidemics, the commensal black rat and the sewer rat and their fleas have been the principal sources of epidemics.

Clinical Features

Plague is an acute, severe bacterial infection which has three main forms depending on the route of infection: bubonic, pneumonic and septicaemic. Other forms of plague disease such as meningitis and pharyngitis are seen but are rare. Initial symptoms of plague usually include acute febrile illness with other symptoms such as fever, chills, muscle aches, nausea and lethargy (Public Health England, 2017).

Bubonic plague

Bubonic plague is the most common form of plague. Bacteria enter at the flea bite site and travel through the lymphatic system to cause lymphadenitis in proximal lymph nodes. The lymph node then becomes inflamed, tense and painful, and is called a "bubo". At advanced stages of the infection the inflamed lymph nodes can turn into suppurating open sores (World Health Organisation, 2017).

Symptoms may include:

  • sudden onset of fever, headache, sore throat, chills, myalgia lethargy
  • painful lymph node/s (bubo/es), most commonly the inguinal; less commonly the axillary and cervical nodes
  • the nodes are tender, firm and fixed, and may suppurate in the second week
  • bacteraemia can result in spread to a range of organs including the meninges and the lungs, where it causes a rapidly progressing pneumonia (see pneumonic plague).

Pneumonic plague

Pneumonic or lung-based plague is the most virulent and severe form of plague, and is usually rare. Left untreated pneumonic plague is almost always fatal, and mortality is very high in persons whose treatment is delayed beyond 24 hours after symptom onset (Bennett, 2014; Public Health England, 2017; World Health Organisation, 2017). Pneumonic plague occurs in two forms, primary and secondary.

Typically, the pneumonic form is caused by spread to the lungs from advanced bubonic plague (secondary pneumonic plague).

Primary pneumonic plague results from direct inhalation of bacteria into the lungs.

Symptoms may include:

  • fever, headache, weakness and tachycardia
  • rapid onset of pneumonia with dyspnoea, chest pain and cough
  • sputum is mucoid at first and then progresses to haemoptysis
  • ± buboes.

Septicaemic plague

Septicaemic plague occurs when infection spreads through the bloodstream. Advanced stages of the bubonic form of plague will also lead to direct spread of Y. pestis in the blood (World Health Organisation, 2017).

  • it can occur without lymphadenopathy (primary septicaemic plague)
  • both bubonic and pneumonic plague may progress to septicaemic plague (secondary septicaemic plague)
  • fever, shock, purpura, distal gangrene, ± bubo, ± gastrointestinal symptoms
  • sepsis may lead to disseminated intravascular coagulation.

Plague meningitis

Plague meningitis is a rare complication that can occur acutely or as a delayed manifestation as a result of inadequate treatment.

Mode of Transmission

  • In affected counties rodent to person transmission occurs via the bite of an infected flea.
  • Person to person transmission occurs via inhalation of infected droplets spread by coughing patients with pneumonic plague or secondary plague pneumonia or pharyngitis.
  • Possible aerosol transmission many also occur after unprotected handling of tissues of infected animals or laboratory specimens or deliberate release (bioterrorism) of aerosolised bacteria.
  • In endemic countries (not in Australia), cats have occasionally transmitted infection via bites, scratches or respiratory droplets and have been a source of infection to veterinary personnel.

Incubation period

Usually from 2  to 7 days following the bite of an infected flea or between 1 to 4 days following inhalation of infected respiratory droplets. (Centers for Disease Control and Prevention, 2017; Heymann, 2015).

Period of Communicability

  • Infected fleas may remain infectious for several months.
  • Bubonic plague is not usually transmitted from person to person unless there is contact with pus from suppurating buboes.
  • Pneumonic plague may be highly communicable under appropriate climatic conditions and conditions of overcrowding.
  • Most patients are likely to remain infectious for 48-72 hours after commencing appropriate antibiotic treatment (Richard V, 2015; National Health and Medical Research Council, 2017; Heymann, 2015).

Susceptibility and Resistance

Everyone is susceptible to infection. Infection does not always confer protective immunity.

Management

Cases

Investigation
In consultation with the attending medical practitioner, attempt to identify the source of infection, and document any recent overseas travel.

Restriction
Infection management and isolation requirements of suspected or confirmed cases of plague, including stepping down of requirements, should be made based on a detailed risk assessment carried out in conjunction with an infectious diseases physician or specialist.

For patients with bubonic plague (if there is no cough and their chest Xray film shows no feature of pneumonia):  
Standard precautions should be used for all patient interactions. Contact with infectious fluids should be avoided when managing patients with bubonic plague who do not have respiratory symptoms. Most patients are likely to remain infectious for 48-72 hours after commencing appropriate antibiotic treatment (Richard V et al., 2015; National Health and Medical Research Council, 2017; Heymann, 2015).

For patients with pneumonic plague:
Droplet transmission-based precautions in conjunction to standard precautions are required for patients with pneumonic plague. The patients should be placed in a single room ideally with negative pressure. Most patients are likely to remain infectious for 48-72 hours after commencing appropriate antibiotic treatment and there has been a favourable clinical response (Richard V et al., 2015; National Health and Medical Research Council, 2017; Heymann, 2015). The decision to step down precautions will be based on their clinical response, laboratory results and expert advice of the Infectious Diseases Physician.

Confirmed cases of pneumonic plague should be kept under droplet precautions until sputum cultures are negative (Centers for Disease Control and Prevention,1996).

Treatment
Cases should be investigated and treated under the supervision of an Infectious Diseases Physician. Recommended antibiotic treatment includes gentamicin, doxycycline or ciprofloxacin. All are highly effective if used early (Centers for Disease Control and Prevention, 2017). Recommended antibiotic treatment advice is available: https://www.cdc.gov/plague/resources/Recommended-antibiotics-for-plague_revision-Aug-2015_Final-%2800000002%29.pdf.

Counselling
The case should be advised of the nature of the infection and its mode of transmission.

Contacts

Contact Tr
Yes.

Definition

A close contact is defined as a person who has had face-to-face exposure to an infectious case of pneumonic plague, including health care workers, in the previous seven days. People who have had direct, unprotected exposure to suppurative discharge from a case of bubonic plague in the previous seven days may also be considered as a close contact.

In endemic areas overseas, close contacts also include persons who are likely to have been exposed to infected rodents or fleas in the same household as the case in the last seven days.

Determine whether any contacts have any symptoms consistent with plague and, if so, organise appropriate clinical review and investigation.

Investigation
Every effort should be made to trace the source of the infection and contacts.

Restriction
Contacts should be placed under surveillance by the Public Health Unit for seven days to monitor for symptoms.

Prophylaxis
Close contacts should be strongly recommended to take appropriate antibiotic prophylaxis for seven days. For further guidance on post-exposure prophylaxis see https://www.cdc.gov/plague/resources/Recommended-antibiotics-for-plague_revision-Aug-2015_Final-%2800000002%29.pdf.

Counselling
The contact should be advised of the nature of the infection, its mode of transmission, and the reason for and duration of follow-up.

Other control measures

Identify Source
A single case of plague constitutes an outbreak and should be considered as a public health emergency.

The actual or probable source of infection must be determined and preventive measures undertaken.

If one or more cases are found with no history of travel to an endemic plague area, a deliberate release of plague bacteria must be considered.

Environmental Evaluation
The actual or probable source of infection must be determined and preventive measures undertaken. Treat clothes, habitation and domestic pets for fleas if a possible source of infection.

Preventive Measures

Vaccination
Currently there is no commercially available vaccine available, however vaccine research continues in this area.

Flea and Rodent control
Chemoprophylaxis is recommended for those entering high risk areas e.g. aid workers during a plague epidemic. See “advice for travellers” for further information.

Both the relevant State Chief Biosecurity Officer and the Department of Biosecurity Medical Officer should be notified immediately of a suspected or confirmed case of plague.

Advice for travellers

All travellers to endemic areas should seek advice four to six weeks before travelling. They should be aware of the risks and the potential outcome of infection, and the measures they can undertake to reduce these risks as well as where to seek medical treatment should they become unwell during their travels. Currently there is no commercially available vaccine to protect against plague.

Prevention measures include:

  • WHO recommends a personal insect repellent containing DEET, IR3535, Icaridin (KBR3023) or Picaridin. Always use in accordance with the manufacturer’s instructions.
  • avoid contact with dead animals, infected tissues or materials
  • avoid close contact with patients with symptoms of pneumonic plague
  • avoid crowded areas where cases of pneumonic plague have been recently reported

Unwell travellers who have been to areas where plague occurs, and who may have had contact with rodents or fleas or anyone with symptoms or diagnosed with pneumonic plague, should seek prompt medical advice with details of their travel history and activities (Public Health England, 2017; World Health Organisation, 2017).

Summary

Prepare a report of the investigation for the Communicable Diseases Branch, Queensland Health.

References

  • Bennett, J. D. (2014).Mandell, Douglas, and Bennett's Principles and practice of infectious diseases.Elsevier Health Services.

  • Centers for Disease Control and Prevention. (1996, December 13). Prevention of Plague. Retrieved November 01, 2017, from Centers for Disease Control and Prevention: https://www.cdc.gov/mmwr/PDF/rr/rr4514.pdf

  • Centers for Disease Control and Prevention. (2017, October 23). Plague. Retrieved October 30, 2017, from Centers for Disease Control and Prevention: https://www.cdc.gov/plague/index.html

  • Guerrant, R. W. (2011). Tropical Infectious Diseases: Principles, Pathogens and Practice E-Book. Elsevier Health Sciences.

  • Heymann, D. (2015). Control of communicable diseases manual 20th Edition. American Public Health Association.

  • National Health and Medical Research Council. (2017, June 15). Australian Guidelines for the Prevention and control of Infection in Healthcare (2010 Guidelines). Retrieved November 01, 2017, from National Health and Medical Research Council: https://www.nhmrc.gov.au/guidelines-publications/cd33

  • Public Health England. (2017, October 24). Plague epidemiology, outbreaks and guidance. Retrieved October 31, 2017, from Public Health England: https://www.gov.uk/guidance/plague-epidemiology-outbreaks-and-guidance

  • Richard, V., Riehm J.M., Herindrainy, P. (2015, January). Pneumonic Plague Outbreak, Northern Madagascar, 2011. Emerging Infectious Diseases, 21(1).

  • World Health Organisation. (2017, October 02). Plague - Madagascar. Retrieved October 31, 2017, from World Health Organisation: http://www.who.int/csr/don/02-october-2017-plague-madagascar/en/

  • World Health Organisation. (2017, October). Plague fact sheet. Retrieved October 30, 2017, from World Health Organisation: http://www.who.int/csr/disease/plague/en/

Last updated: 1 December 2017