In Colorado rodents and other animals may become infected with plague and die. Their fleas may then bite another animal or person and transmit the infection.

Clinical Description

Plague is a severe bacterial infection characterized by the abrupt onset of high fever, chills, malaise, myalgia, nausea, and weakness.

There are three main clinical forms of plague:

• The most common form is the bubonic plague characterized by the development of painful, unilateral regional lymphadenopathy within 24-48 hours of fever onset. The affected lymph nodes drain the point of entrance of the bacteria, typically involving the inguinal, axillary or cervical nodes.
• Septicemic plague may develop secondary to the bubonic form, or may be the primary presentation if the bacteria are directly inoculated into the blood stream. This presents as a gram-negative bacterial sepsis.
• Pneumonic plague can develop as a primary infection from inhalation of respiratory droplets or secondarily from hematogenous dissemination.

Pneumonic plague can result in human-to-human transmission via spread through respiratory droplets. Untreated bubonic plague has a fatality rate approaching 70%; septicemic and pneumonic plague are fatal without prompt treatment.

Diagnosis

Although the majority of patients with plague present with a bubo (enlarged painful lymph node), some may have nonspecific symptoms. For example, septicemic plague can present with prominent gastrointestinal symptoms such as nausea, vomiting, diarrhea, and abdominal pain. Appropriate diagnostic samples include blood cultures, lymph node aspirates if possible, and/or sputum, if indicated. Drug therapy should begin as soon as possible after the laboratory specimens are taken. If plague is suspected, local and state health departments should be notified immediately. If the patient has pneumonic signs, he/she should also be isolated and placed on droplet precautions.

Diagnostic Testing

Plague is a 24-hour reportable condition

Report should be made on any suspected cases of plague based on the healthcare provider's clinical impression or preliminary laboratory results

Suspect cases should be reported immediately by telephone.

CDPHE Reporting Phone Number:
Business Hours (Mon-Fri 8:30 am-5:00 pm) - 303-692-2700
After-hours: 303-370-9395
Larimer County Department of Health and Environment: 970-498-6700

If plague is suspected, pre-treatment specimens should be taken if possible, but treatment should not be delayed. Specimens should be obtained from appropriate sites for isolating the bacteria, and depend on the clinical presentation:

• Lymph node aspirate: An affected bubo should contain numerous organisms that can be evaluated microscopically and by culture.
• Blood cultures: Organisms may be seen in blood smears if the patient is septicemic. Blood smears taken from suspected bubonic plague patients early in the course of illness are usually negative for bacteria by microscopic examination but may be positive by culture.
• Sputum: Culture is possible from sputum of very ill pneumonic patients; however, blood is usually culture-positive at this time as well.
• Bronchial/tracheal washing may be taken from suspected pneumonic plague patients; throat specimens are not ideal for isolation of plague since they often contain many other bacteria that can mask the presence of plague.
• In cases where live organisms are unculturable (such as postmortem), lymphoid, spleen, lung, and liver tissue or bone marrow samples may yield evidence of plague infection by direct detection methods such as direct fluorescent antibody (DFA) or PCR.

Y. pestis may be identified microscopically by examination of Gram, Wright, Giemsa, or Wayson's stained smears of peripheral blood, sputum, or lymph node specimen. Visualization of bipolar-staining, ovoid, Gram-negative organisms with a "safety pin" appearance permits a rapid presumptive diagnosis of plague.

If cultures yield negative results, and plague is still suspected, serologic testing is possible to confirm the diagnosis. One serum specimen should be taken as early in the illness as possible, followed by a convalescent sample 4-6 weeks or more after disease onset.

Recommended antibiotic treatment for plague

Begin appropriate therapy as soon as plague is suspected. The drugs of choice are streptomycin or gentamicin, but tetracyclines, fluoroquinolones and chloramphenicol are also effective. Duration of treatment is 10 days, or until 2 days after fever subsides. Oral therapy may be substituted once the patient improves.

The regimens listed below are guidelines only and may need to be adjusted depending on a patient's age, medical history, underlying health conditions, or allergies.

Treatment of Plague

Adapted from: Inglesby TV, Dennis DT, Henderson DA, et al. Plague as a biological weapon: medical and public health management. Working Group on Civilian Biodefense. JAMA. 2000 May 3;283(17):2281-90.

1 Aminoglycoside dose should be adjusted in patients with impaired renal function.
2 Chloramphenicol serum concentration should be 5-20 ug/mL to avoid bone marrow suppression.
3 Gentamicin is pregnancy category C but has been used safely and effectively for treatment of plague in pregnant women.
4 Doxycycline and ciprofloxacin are pregnancy categories D and C, respectively. These agents should be administered only if gentamicin is not available.

Adults Preferred agentsDoseRoute of administration

Streptomycin11 g twice dailyIM

Gentamicin15 mg/kg once daily, or 2 mg/kg loading dose followed by 1.7 mg/kg every 8 hoursIM or IV

Alternative agentsDoseRoute of administration

Doxycycline100 mg twice daily or 200 mg once dailyIV

Ciprofloxacin400 mg twice dailyIV

Moxifloxacin and Levafloxacin have also been approved by FDA for plague. See package insert for prescribing information and dosages

Chloramphenicol225 mg/kg every 6 hoursIV