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Bubonic Plague

Transmitted by flea bite or direct contamination of an open skin lesion by plague-infected material. The infection spreads via the lymphatics to the regional lymph nodes causing inflammation and swelling in one or several nodes (buboes).

Following inoculation a local cutaneous proliferation, not usually clinically evident, ensues. In some cases, a vesicle, pustule, or ulcer develops at the inoculation site. The infection spreads via the lymphatics to the regional lymph nodes causing inflammation and swelling in one or several nodes (buboes). Buboes may occur in any regional lymph node sites including inguinal, axillary, supraclavicular, cervical, post-auricular, epitrochlear, popliteal or pharyngeal. Deeper nodes (such as intrabdominal or intrathoracic nodes) may also be involved through lymphatic or hematogenous extension.

Septicaemic Plague

Primary septicaemic plague is a progressive, overwhelming bloodstream infection with Y. pestis in the apparent absence of a primary lymphadenopathy. Septicaemic plague can be primary or secondary to bubonic plague.

The presence of rapidly replicating Gram-negative bacilli in the bloodstream initiates a self-perpetuating immunological cascade typically linked to host response to severe injury, in this case the agent inciting injury is bacterial endotoxin. The host response may result in a wide spectrum of pathological events including disseminated intravascular coagulopathy (DIC), multiple organ failure (MOF), and adult respiratory distress syndrome (ARDS).

Pneumonic Plague

The incubation period is usually 1-3 days (1,14,15).

Plague pneumonia occurs in two distinct and epidemiologically significant forms. Secondary plague pneumonia results from haematogenous spread of Y. pestis to the lungs. This invasive infection provokes a masked inflammatory response and results in bacterial multiplication in pulmonary tissue. This process then spills over into the alveolar spaces and provides a mechanism for Y. pestis to be expelled during coughing episodes.

A primary pneumonic plague patient usually has an infectious pneumonitis at the onset of symptoms, often within 24 to 48 hours after exposure.

Pharyngeal Plague

Plague pharyngitis results from contamination of the oropharynx with Y. pestis-infected material from respiratory droplets expelled during coughing by a patient (or animal) with a respiratory plague infection, or ingestion of undercooked or raw tissues of an infected animal.

Meningeal Plague

Meningeal plague may be a primary manifestation, but it usually occurs a week or more after the onset of bubonic or septicaemic plague.

It is often associated with delayed, inappropriate or bacteriostatic antibiotic therapy and is more common in patients with axillary (as opposed to inguinal) buboes.