Introduced Species Summary Project
Bubonic Plague (Yersinia pestis)
Scientific Name: Yersinia pestis
Classification: Bacteria, micro-organism
Phylum or Division:
Identification: Yersinia pestis, or plague, is a zoonotic bacterial infection transmitted by way of the flea parasite. The plague infection is typically spread from one rodent to another after a flea has bitten and ingested contaminated blood. When the flea has lost its natural host, the rat, it will seek out other sources within the environment. It is at this point that the flea becomes an increased risk to humans and animals within the immediate area. Three forms of plague currently exist, including bubonic, septic and pneumonic plague. Bubonic plague is the most frequent form of infection which targets the lymphatic system. Infected persons will develop enlarged lymph nodes resulting in open sores at advanced stages. Septic plague, or Black Plague, attacks the bloodstream. Numerous black patches appear over the body due to sub dermal hemorrhages throughout the skin. Transmission of pneumonic plague can occur between humans without the involvement of the flea parasite. Although pneumonic plague is the least common form of transmission, it is the most contagious and holds the highest mortality rate.
The plague was linked to the Yersinia pestis bacteria by a Swiss scientist, Alexandere Yersin in 1894
Distribution: Plague has continued to exist within focal endemic wildlife
population throughout the world. This
organism continues to survive within
is no known endemic plague in
Current Distribution: The World Health Organization
reports approximately one to three thousand cases of plague throughout the
planet annually. In 2003, 2,118 cases
were reported nine countries throughout the world. Of the over 2,000 cases and 182 fatalities
98% were from
Site and Date of Introduction: The introduction of the flea carrying parasite into shipping ports is responsible for several pandemics throughout the world. A few significant pandemics are listed below:
Black Plague occurred throughout
the late 17th Century (1665-66),
Mode(s) of Introduction: Throughout the
world, the Y. pestis bacterium is
most commonly spread via the rat flea. In
Reason(s) Why it has Become Established: The plague organisms exist in a stable enzootic state within several wildlife populations throughout the world. Humans are an accidental, dead-end host within the plague life cycle. Plague organisms have been introduced into novel habitats due to human influence. Relocation of humans and animals into unsanitary conditions has lengthened our exposure to these organisms. Plague infections have exploded in some areas when paired with the short incubation period of two to seven days. For the bubonic plague, symptoms can occur within six to eight hours after transmission. If left untreated, septicemia may develop in two to six days. Continued progression of the infection could result in secondary pneumonic plague in as many as 15% of the cases, thus increasing the potential for rapid airborne transmission. If pneumonic plague is left untreated, mortality rate can reach up to 95% in one to six days.
Role: The plague
pandemic did contribute to the depopulation of many areas in
The Great Plague of the late 17th century played a major role in establishing and defining a government’s function where public health is concerned. What lengths does the establishment take to ensure the safety of its citizens?
Benefit(s): When faced with a pandemic, populations are forced to understanding epidemiology, prevention and cures from disease. The emergence of plague has given us a better understanding of how we impact and are impacted by our environment. We have established a better understanding and acceptance of proper hygiene, pest management and quarantine of the trade industry.
After WWII experimentation of
biological warfare included plague organisms.
Control Level Diagnosis: Due to the fact that there are no current pandemics of plague throughout the world, this invasive species should be treated as a Medium Priority level control. Public education, surveillance and vector control should continue throughout all areas where plague is endemic to prevent transmission to novel habitats. With the ability for biological warfare and bioterrorism, planning for pandemic control and prevention are needed.
Control Method: Fortunately, the plague bacterium is highly susceptible to antibiotics and can be easily treated. In 2003, a rapid diagnostic test was developed to obtain reliable results in 15 minutes instead of 15 days with previous testing techniques.
Heightened awareness of public health, sanitation and personal hygiene has been extremely beneficial to the eradication of the plague in medieval times and today.
References & Photo Credits:
Author: Patricia Walsh
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