Download The Plague

The Plague
By Lindsey Castillo
Etiologic Agent:
The Plague is caused by the gram-negative coccobacilli bacteria, which is known as
Yersenia pestis (Walsh).
Name: Yersinia pestis
Classification: Zoonotic Bacteria
Phylum: Proteobacteria
Class: Gammaproteobacteria
Order: Enterbacteriales
Genus: Yersinia
Transmission:
The Plague can be transmitted my many ways. The most common means of transmission
of the Plague is through the bite of an infected flea (2). Many times when there are plague
outbreaks large numbers of rodents tend to die off, causing fleas to find other sources of
blood (2). Common household pets such as cats and dogs are also known for bringing
these fleas home. Another way of transmission is coming into contact with a
contaminated fluid and or tissue from an infected animal. A common example of this is
hunters skinning a plagued animal. The last type of transmission is the only type of
transmission via humans and it is through infectious droplets (2). Whenever a person has
plague pneumonia and coughs there cough may contain infectious droplets, which can be
inhaled by others who are in close proximity.
Reservoirs:
The plague is a zoonotic disease therefore animals are the main reservoirs. Wild rodents
are considered to be the natural reservoirs for the Plague and then they infect other
animals such as household pets (8).
Tests to Identify the Plague:
When it comes to identifying the plague many times doctors will take different samples
and then see if you have the Yersinia pestis bacteria in any of those samples. Some of
those samples can be taken from swollen lymph nodes aka buboes, your blood, and from
sputum (7).
Signs and Symptoms:
There are three different forms of the plague and they all have different symptoms. The
first type is the bubonic plague, which is often characterized by fever, chills, headache,
and painful swollen lymph nodes, which are called buboes (10). Septicemic plague is the
2nd type of plague that can develop from untreated bubonic plague and its symptoms
consist of fever, abdominal pain, shock, weakness, and sometimes bleeding into organs
and skin (10). Many times with Septicemic plague the skin and tissue located on
extremities such as toes, hands, and arms begin to turn black and die (10). The last type
of plague is the pneumonic plague; the symptoms are fever, chest pain, cough, headache
and occasionally bloody mucous (10).
Historical Information:
Alexandre Yersin a member of the French Colonial Health Services was the first to
discover Yersinia pestis the bacteria that causes the Plague (3). He discovered the
bacteria in 1894 while in Hong Kong investigating the bubonic plague outbreak (3). He
was able to identify the bacteria by isolating samples from buboes of infected patients
(3). Shortly after discovering the bacteria it was named after him.
Virulence Factors:
One of the major virulence factors of Yersinia pestis is its short incubation period, which
is from 1-3 days (4). One virulence factor is that, “the LPS structure diversities of
Yersinia pestis during transition between flea and host temperatures make the bacteria
resistant to the serum-mediated lysis and suppress the pro-inflammatory response” (4).
Another virulence factor is its resistance to serum.
Control/ Treatment:
If anyone has been infected with the Plague they should receive treatment immediately.
Due to the severity of the Plague, if treatment is not received within 24 hours after the
first sign of symptoms death may occur. There are many antibiotics that can be used
some of those are gentamicin, doxycycline, streptomycin and ciprofloxacin (1). As well
as antibiotics “…oxygen, intravenous fluids, and respiratory support are also needed” (1).
If infected with pneumonic plague one should be isolated from others due to how easy it
is for others to contract.
Prevention:
Prevention for the plague consists of avoiding rodents, using gloves while handling
animals that may be infected, using bug repellent, and protecting household pets from
fleas (6). There are vaccines for the Plague, but according to the World Health
Organization they have “… not been shown to be very effective against plague” (9).
Although vaccines are not recommended they are still given to at risk groups such as
laboratory workers.
Outbreaks:
There have been three recorded major plague pandemics. The first recorded incident was
the Justinian Plague, which began in 541 AD (5). This pandemic consisted of frequent
outbreaks over a 200-year period and ended up killing 25 million people (5). The second
pandemic is known as the “Black Death” or the Great Plague. This outbreak started in
China in 1334 (5). Slowly after its origination in China it began to spread along the great
trade routes, infecting Constantinople and then Europe (5). The Black Death wiped out
entire towns and nearly 60% of European’s population. Although this awful event did
quite a bit of harm, it did help speed up development and is said to be “…considered a
factor in the emergence of the Renaissance in the late 14th century” (5). The third
pandemic or the Modern Plague also began in China but many years later in the 1860s
(5). Over a span of 20 years it started to spread to different port cities and then appeared
in Hong Kong in 1894 (5). The Modern Plague caused about 10 million deaths, but
allowed scientists to determine what the causative agent was and how it was spread (5).
The more recent endemics have occurred in India during the beginning of the 20th century
and during the 1960s and 70s in Vietnam (5). Today the plague is “… found in subSaharan Africa and Madagascar, areas which now account for over 95% of reported
cases” (5). Most of the human cases found today are located in northern New Mexico,
northern Arizona, California, southern Oregon, and parts of Colorado (12). Although
there are still outbreaks today there are less than 20 per year in the United States, and
most of them have been treatable cases (12). According to the CDC “over 80% of the
United States plague cases have been the bubonic form” (12).
References
1. Dugdale, David. "Plague." The New York Times Health Guide. The New York Times, 9
June 2011. Web. 6 Dec. 2015.
<http://www.nytimes.com/health/guides/disease/plague/overview.html>.
2. "Ecology and Transmission." Centers for Disease Control and Prevention. Centers for
Disease Control and Prevention, 13 June 2012. Web. 4 Dec. 2015.
<http://www.cdc.gov/plague/transmission/index.html>.
3. Hawgood, Barbara. "Result Filters." National Center for Biotechnology Information. U.S.
National Library of Medicine. Web. 6 Dec. 2015.
<http://www.ncbi.nlm.nih.gov/pubmed/18653838>.
4. Li, Bei, and Ruifu Yang. "American Society for Microbiology Infection and Immunity."
Interaction between Yersinia Pestis and the Host Immune System. 4 Feb. 2008. Web.
6 Dec. 2015. <http://iai.asm.org/content/76/5/1804.full>.
5. "Plague History." Centers for Disease Control and Prevention. Centers for Disease
Control and Prevention, 18 Nov. 2014. Web. 6 Dec. 2015.
<http://www.cdc.gov/plague/history/>.
6. "Plague Prevention." Centers for Disease Control and Prevention. Centers for Disease
Control and Prevention, 27 Nov. 2013. Web. 6 Dec. 2015.
<http://www.cdc.gov/plague/prevention/>.
7. "Plague Tests." Tests and Diagnosis. Mayo Clinic, 26 Mar. 2013. Web. 4 Dec. 2015.
<http://www.mayoclinic.org/diseases-conditions/plague/basics/tests-diagnosis/con20021610>.
8. "Plague." Vermont Department of Health. Web. 4 Dec. 2015.
<http://healthvermont.gov/prevent/Plague.aspx>.
9. "Plague." WHO. World Health Organization, 1 Nov. 2014. Web. 6 Dec. 2015.
<http://www.who.int/mediacentre/factsheets/fs267/en/>.
10. "Symptoms." Centers for Disease Control and Prevention. Centers for Disease Control
and Prevention, 13 June 2012. Web. 6 Dec. 2015.
<http://www.cdc.gov/plague/symptoms/>.
11. Walsh, Patricia. "Invasion Biology Introduced Species Summary Project - Columbia
University." Invasion Biology Introduced Species Summary Project - Columbia
University. Columbia University, 14 Nov. 2005. Web. 6 Dec. 2015.
<http://www.columbia.edu/itc/cerc/danoffburg/invasion_bio/inv_spp_summ/Yersinia_pestis.htm>.
12. "Plague Maps." Centers for Disease Control and Prevention. Centers for Disease
Control and Prevention, 24 Aug. 2015. Web. 6 Dec. 2015.
<http://www.cdc.gov/plague/maps/>.