Yersinia pestis Agent Information Sheet

Boston University
Research Occupational Health Program (ROHP)
617-358-7647

Agent

Gram negative rod-ovoid 0.5-0.8 µm in width and 1-3 µm in length (safety pin appearance), bipolar staining (Giemsa) facultative intracellular, non-motile.

Disease/Infection

Y. pestis causes a zoonotic disease of rodents and in humans can take the form of bubonic, septicemic or pneumonic plague.

Pathogenicity

Humans generally contract the disease through contact with infected rodents or their fleas.

Bubonic plague may occur 2-8 days after the bite of an infected flea with rapid onset of symptoms of high fever, severe malaise, headache, myalgias, and sometimes nausea and vomiting. Buboes (swollen and extremely painful infected lymph nodes) usually develop at the same time as symptoms are generally 1-10 cm in diameter. In natural infections these buboes usually develop in the femoral or inguinal lymph nodes because fleas generally bite on the legs, however a laboratory acquired infection might be more likely to develop buboes in the brachial lymph nodes.

Septicemic plague occurs when the bacteria enters the bloodstream it occurs in 10-20% of plague cases. This can occur with or without the formation of buboes. Without treatment septicemic plague is 100% fatal. With treatment there is a 30 to 50% survival rate.

Pneumonic plague occurs when the lungs become infected either from the blood stream for from inhaling the bacteria. An infectious dose is < 100 colony forming units. Patients with primary pneumonic plague develop symptoms within 1- 6 days. Without treatment it is 100% fatal. When untreated there is a 60 % mortality rate. Pneumonic plague is the only form of plague which is readily transmissible from person to person. From past plague epidemics the secondary infection rate is estimated to be 1.3 cases per primary case.

Biosafety Information

Risk Group/BSL
Risk Group 3
Biosafety Level 3 Practices

Modes of Transmission
Handling infected tissues, airborne droplet, or manipulation of lab cultures

Host Range/Reservoir
Wild rodents (rats) are the natural reservoir; lagomorphs (rabbits, hares) and carnivores may be a source of infection to humans. Vectors include Wild rodent fleas, especially the oriental rat flea (Xenopsylla cheopis); occasionally by human fleas (Pulex irritans)

Symptoms
Patients with bubonic plague present with local lymphadenitis with fever, chills, weakness, and headache. Septicemic patients can have bacterial blood stream infection leading to shock and death without necessarily presenting with buboes.

With pneumonic plague, the first signs of illness are fever, headache, weakness, and rapidly developing pneumonia with shortness of breath, chest pain, cough, and sometimes bloody or watery sputum. The  pneumonia progresses for 2 to 4 days and may cause respiratory failure and shock. Without early treatment, patients may die.

Incubation Period
2 to 6 days; may be a few days longer in vaccinated individuals; for primary plague pneumonia, 1 to 6 days

Viability
Susceptible to many disinfectants – 1% sodium hypochlorite, 70% ethanol, 2% glutaraldehyde, iodines, phenolics, formaldehyde. Sensitive to moist heat (121° C for at least 15 min) and dry heat (160-170° C for at least 1 hour)

Survival Outside Host
Blood – 100 days; human bodies – up to 270 days

Information for Lab Workers

Laboratory PPE

Gloves should be worn when handling field-collected or infected laboratory rodents and when there is the likelihood of direct skin contact with infectious materials; gown with tight cuffs and ties in back or the equivalent should be worn when manipulating cultures and specimens; a N95 should be worn when there is a risk of contact with aerosols.

Containment

BSL-3/ABSL-3 practices, containment equipment, and facilities are recommended for all activities involving the handling of potentially infectious clinical materials and cultures. Additionally, all work including necropsies of potentially infected animals should be performed in a BSC with special care given to avoid the generation of aerosols.

BSL-3 is recommended for activities with high potential for droplet aerosol production and for activities involving large-scale production or high concentrations of infectious materials.

In Case of Exposure/Disease

• For injuries in the lab which are major medical emergencies (heart attacks, seizures, etc…):
  • Medical Campus: call or have a co-worker call the Control Center at 617-414–4444.
  • Charles River Campus: call or have a co-worker call BU Police at 617-353-2121.
    You will be referred to or transported to the appropriate health care location by the emergency response team.
• For lab exposures (needlestick injuries, cuts, scratches, splashes, animal bites etc…) involving this infectious agent, or for unexplained symptoms or illness:

• You will be connected with the BU Research Occupational Health Program (ROHP) medical officer. ROHP will refer you to the appropriate health care location.
• Under any of these scenarios, always inform the physician of your work in the laboratory and the agent(s) that you work with.
• If you have been given a wallet-sized agent ID card, provide the ID card to the physician.

Vaccination

Previously formalin-killed vaccine, Plague Vaccine U.S.P., was available for use by persons who worked with    Y. pestis in the laboratory setting. However, this was not protective against inhalation exposures and is no longer available. Research is underway for new vaccine targets. There is a vaccine available in other countries but not currently in the United States.

Information for First Responders/Medical Personnel

Public Health Issues

Person to person transmission only occurs in pneumonic disease and generally with close contact or in patients with copious sputa and not through aerosolized particles or droplet nuclei. However, to prevent person-to-person transmission, patients with suspected pneumonic plague should be managed in isolation under respiratory droplet precautions. Respiratory droplet precautions include the use of fitted masks, gowns, gloves, and protective eyewear when providing direct patient care. Those without respiratory symptoms can be managed with standard precautions.

Outside providers should call ROHP in case of either infection or exposure for further instructions.

Diagnosis/Surveillance

Monitor for symptoms; organism can be isolated in blood or clinical specimen cultures-presumptive diagnosis is made by visualizing bipolar staining, ovoid, gram-negative organisms in sputum or material aspirated from bubo; FA and ELISA test; PHA using Fraction-1 antigen.

First Aid/Post Exposure Prophylaxis

Doxycycline is the prophylactic agent of first choice, given in an adult dose of 100 mg twice daily for 7 days. Antibiotics can be used for chemoprophylaxis against plague in laboratory workers thought to have had an infective exposure within the previous 7 days. Alternative drug is Ciprofloxacin 500 mg BID for 7 days or levofloxacin 500 mg daily for 7 days.

Perform one of the following actions:

Treatment

Antibiotic therapy in early stages (8 to 24 hours after onset of pneumonic plague); secondary infection or suppurative bubo may require incision and drainage. Gentamycin is the antibiotic of choice or doxycycline in patients who are aminoglycoside allergic. Chloramphenicol should be used in settings were high tissue penetration is required such as myocarditis, meningitis or pleuritis.

References

Public Health Agency of Canada: http://www.phac-aspc.gc.ca/lab-bio/res/psds-ftss/msds169e-eng.php

CDC: http://www.cdc.gov/plague/transmission/index.html

CDC BMBL: https://www.cdc.gov/labs/pdf/SF__19_308133-A_BMBL6_00-BOOK-WEB-final-3.pdf

Mandell, G. L., J. E. Bennett, et al. (2010). Mandell, Douglas, and Bennett’s principles and practice of infectious diseases. Philadelphia, PA, Churchill Livingstone/Elsevier.

Revised: 11/8/2013