Disease Transmission, Prevention, and Treatment

Xenopsylla cheopis

The bubonic plague is the most prevalent of three main types of plague caused by the bacteria Yersinia pestis (1). The main host organisms for bubonic plague are rodents and lagomorphs including but not limited to rats, prairie dogs, chipmunks, and mice. The host animals are infected through flea bites, and when they in turn become septicemic, will spread the bacteria into any flea that comes into contact with them (2). 

Plague Doctor wearing
protective clothing with a
beak containing herbs and
perfumes that were thought
to purify the air (3)

Infected fleas can then go on to infect other members of the host species as well as organisms that are not the intended hosts. These hosts are referred to as incidental hosts, consisting of mammalian
species including bobcats, mountain lions, humans, etc (2). While these species are not the intended hosts, they can still acquire the disease and have the potential to spread it to each other, potentially leading to a pandemic such as the Black Death.

In humans, bubonic plague is transmitted through the bites of infected fleas of the species Xenopsylla cheopis, also known as the oriental rat flea (2). Transmission can also occur person to person, through contact with bodily fluids of infected individuals, contact with contaminated materials, or inhalation of particles from those infected with the pneumonic plague (1).

Spread of Bubonic plague during pandemic: "Black Death" (6)

Even though humans are not the host species for the plague, the ability to pass the disease from one person to another along with the cramped and unsanitary conditions that we lived in at the time of the major pandemics allowed the illness to become so widespread. At the times of the pandemics, the disease seemed to frequently begin in china and spread like wildfire to Europe, Africa, the middle east, basically anywhere with a trade route.

Cases of Bubonic Plague 2010-2015 (3)

Since the introduction of antibiotics and other sanitary measures that are meant to keep fleas and rodents away from us, the disease has receded and 95% of the cases are restricted to sub-Saharan Africa and Madagascar. The other 5% are found worldwide but due to prevention measures and out ability to recognize and treat the disease effectively the outbreaks tend to be small.




Bubonic plague requires immediate treatment by antibiotics. While the death rate is quite low with treatment, if the patient is left untreated for more than 24 hours, the risk of death increases. Antibiotics such as streptomycin, gentamicin, doxycycline, and ciproflaxin are used to take care of the bacteria. Oxygen, intravenous fluids, and respiratory support are often used to help stabilize the patient and keep them alive while the antibiotics deal with the bacteria (5).

Flea bite (5)

In order to prevent the disease from spreading in the first place, control and monitoring of rats and fleas is recommended (5, 1). If one is in a location where plague is present, the best mode of prevention is to avoid contact with fleas as well as carcasses of infected animals. Contact with infected persons or their bodily fluids or tissues is not recommended (5), and barrier protection such as masks is recommended when in contact with infected persons (2).

Vaccines against the plague exist but are not recommended, except for those who are at a high risk of infection such as those who frequently work with the bacteria, either with patients or in the lab (1).

While the disease has vary low prevalence in modern society, and we have ways of defending ourselves from outbreaks, there is more we could do to. The main recommended preventative measures focus on avoiding infection (5), but actively seeking to prevent it in high prevalence areas such as sub-Saharan Africa and Madagascar by screening for infected people and animals, or giving vaccines to people in those areas can help to create herd immunity and lower prevalence.

      References
(1) http://www.who.int/mediacentre/factsheets/fs267/en/
(2) http://www.cfsph.iastate.edu/Factsheets/pdfs/plague.pdf
(3) https://www.cdc.gov/plague/maps/index.html
(4) http://animaldiversity.org/collections/contributors/Grzimek_insects/Siphonaptera/Xenopsylla_cheopis/medium.jpg
(5) https://medlineplus.gov/ency/article/000596.htm
(6) http://blogs.biomedcentral.com/bugbitten/wp-content/uploads/sites/11/2015/03/the-spread-of-the-black-death.png