Plague
Rare, fatal but easy to treat

Historically, plague was responsible for widespread pandemics with high mortality. During the fourteenth century, it was known as the Black Death, killing one third of the population in Europe. Today, plague is easily treated with antibiotics and rare but still some pockets of the disease remain spread throughout the world. Plague is mostly found in the Democratic Republic of the Congo, Madagascar, and Peru.

It is hard to know how many people are yearly infected. In developing countries few cases are reliably diagnosed and reported. An estimated two thousand people get plague per year but the actual number could be higher.

?

THOUSAND

New infections per year

/

2

THOUSAND

Reported cases

/

10

%

Mortality

What causes Plague

The Plague is caused by the bacterium yersinia Pestis. Y. pestis can be divided into three types: Antiqua, Medievalis, and Orientalis. The organisms that historically caused large pandemics still exist in wild animal reservoirs in some parts of the world, mainly in rodents. Occasionally it spills over from these reservoirs to affect people or other animals.

People most commonly acquire plague when they are bitten by a flea that is infected with the plague bacteria. More than 30 species of fleas are capable of transmitting the disease. Handling of contaminated animals or spread between people is also possible.

Photo: The Oriental rat flea (Xenopsylla cheopis) engorged with blood, the main vector of Y pestis

Where is Plague found

Plague can be found in parts of Africa, the Middle East, Asia, North and South America, and Madagascar. Countries with the most reported cases include the Democratic Republic of the Congo, Madagascar and Peru. A 2017 outbreak in Madagascar infected nearly 2 350 people and killed more than 200.  Globally, the distribution of this organism is in patches.

The geographical distribution of each variant varies. The Antiqua biovar occurs in Africa and Central Asia, and the Medievalis biovar seems to be found mainly in Central Asia but can sometimes be found in Northern Africa as well. The Orientalis biovar can be found in most regions where
plague occurs.

Image: Natural Plague reservoirs

What are the symptoms of Plague

There are three principal forms of Plague: bubonic plague, septicemic plague and pneumonic plague. The incubation period ranges between 2 to 6 days.

  • Bubonic plague is the most common and well known form of  Plague. The bacteria typically comes from a bite wound from an infected animal or flea, and could lead to the development of Septicemic or Pneumonic plague. An enlarged lymph node (bubo) appears near the site of infection. The affected lymph node may develop abscesses, ulcerate and drain.
  • Septicemic plague is the result of lymphatics ultimately draining into the bloodstream. The bacteria may travel to any part of the body. Bacterial endotoxins cause disseminated intravascular coagulation throughout the body and possibly ischemic necrosis. Depletion of the body’s clotting factors leads to bleeding into the skin and other organs, which can cause red and/or black patchy rash and vomiting up blood. Untreated, the septicemic plague is usually fatal.
  • Pneumonic plague arises from infection of the lungs. It causes coughing and airborne droplets that contain bacteria and are likely to infect anyone inhaling them. Initial signs are indistinguishable from several other respiratory illnesses but rapidly progresses to severe disease.
Photo: Swollen lymph glands on a person infected with the bubonic plague.

Other common symptoms are fever, headache and weakness.

How can Plague be prevented

Reduce rodent habitat around your home, work place, and recreational areas. Remove brush, rock piles, junk, cluttered firewood, and possible rodent food supplies. Make your home and outbuildings rodent-proof. Keep fleas off of your pets by applying flea control products.

When out in forested areas, use repellent (containing DEET) on both skin and clothing. Be sure to check for any fleas on pets and do not let them roam alone in certain plague-ridden areas. In addition, to limit contact with wild rodents as they may be carrying infected fleas or the disease itself. If interaction is necessary, use gloves (rubber would be best) to limit exposure to a potential disease vector. In addition, try to stay away from carcasses as it could have the disease in its fluids and/or tissues.

Vaccines have been tested in wildlife species susceptible to plague and may offer a way to control outbreaks.

How is Plague diagnosed

Bubonic plague is the easiest to diagnose as a swollen lymph gland will give clues to the disease. In many cases, there will be no obvious signs that indicate plague. A rapid antigen test can be used or plague can be confirmed using Polymerase chain reaction (PCR) tests, such as the ones made available by the WoIDM. Cultures are not recommended as Y pestis is notoriously slow to grow.

How is Plague treated

Early diagnosis and treatment is essential for survival and reduction of complications. The disease being rare may contribute to delayed diagnosis. Antibiotics and supportive therapy are effective against plague if patients are diagnosed in time. Antibiotics for enterobacteria, such as streptomycin, gentamicin, doxycycline, tetracycline and chloramphenicol, are generally effective.

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