Bubonic Plague Causes and Symptoms

While rare, old-time disease remains as deadly as ever

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The very idea of the bubonic plague is something we associate with the Dark Ages when tens of millions were killed in the wake of the "Black Death" wich swept across Asia, Africa, and Europe in the 14th century. Like smallpox and polio, most of us assumed that the plague had become the stuff of history books, the fodder for costume dramas.

Not so, say disease control experts, who have begun to see a re-emergence of the disease in recent years.

The first such outbreak took place in 1994 in India, which killed 56 people and hospitalized more than 600. Since then, the plague has been positively identified in the Democratic Republic of Congo (65 deaths in 2005), Madagascar (69 deaths in 2014 and 57 more in 2017), and even parts of the U.S (four deaths and 16 infections in 2015). 

As late as June 2017, two New Mexico natives were positively diagnosed with the plague, adding to the 600-plus infections expected globally by the year's end.

Transmission

Bubonic plague is a potentially fatal infection caused by the bacteria Yersinia pestis. The disease is transmitted by the bite of an infected rat flea (Xenopsylla cheopis) which make its home on smaller rodents such as rats, field mice, and squirrels. Because the bacteria is harmless to fleas, it has the perfect vehicle by which to be carried directly from animals to humans.

In addition to smaller rodents like chipmunks and prairie dogs, Yersinia pestis has been found in larger mammals including rabbits, opossum, wild coyotes, and even domestic dogs and cat that have come into contact with rodents.

Symptoms

When a human is infected with Y. pestis, the bacteria travel through the lymphatic system and ends up in the lymph nodes where it causes painful, boil-like enlargements called buboes. This typically happens within one to seven days of exposure and can be accompanied by:

  • Chills
  • High fever
  • Extreme exhaustion
  • Pain
  • Breathing constriction
  • Muscle cramps
  • Vomiting of blood
  • Gangrene of the toes, fingers, lips, and nose
  • Opening of swollen buboes
  • Seizures

Without treatment, the bubonic plague will result in death in 60 percent to 90 percent of cases, usually within 10 days.

Other Forms of the Plague

The route of disease can vary in persons infected by Y. pestis. Rather than traveling from an insect bite to the lymph nodes, the bacteria can enter the body through other routes and cause an entirely different set of symptoms. Among the less common forms of the disease

  • Pneumonic plague occurs when the bacteria is spread to the lungs, usually when an infected person coughs or sneezes on another. While uncommon, it is considered a more serious form of plague, causing the rapid development of pneumonia, chest pains, and bloody or watery sputum, If left untreated, pneumonic plague can cause respiratory failure and death, usually within 36 hours.
  • Septicemic plague occurs when the bacteria find its way directly into the bloodstream, often through a crack or sore in the skin. It is the rarest form of the disease and arguably the most aggressive. Symptoms are similar to that of the bubonic plague but can include characteristic bleeding beneath the skin. Death is almost inevitable if treatment is not delivered within 24 hours.

    Diagnosis and Treatment

    Bubonic plague is diagnosed by running lab cultures on sputum, blood, spinal fluid, or infected lymph nodes. In parts fo the world where the plague is more commonly seen, a rapid dipstick test can usually identify bacterial antigens within 15 minutes.

    Because of the clinical severity of the disease, doctors will usually start treatment presumptively while awaiting lab results. Ideally, treatment should be started within 24 hours, usually in the form of intravenous antibiotics such as streptomycin, doxycycline, or tetracycline. If treated in a timely manner, survival rates can range from 85 percent to as high as 99 percent.

    Prevention

    Key to the prevention of bubonic plague is the avoidance of rodents or any wild animal that can carry fleas. It also requires you to safeguard your property from things that attract animals, like open waste containers or unfenced gardens.

    Additionally, if you live in an area where flea infestations are common:

    • Use a bug repellent spray when outdoors and wear long pants and boots.
    • Never handle sick or dead animals. If you must, wear heavy gloves.
    • Keep your pets indoors or provide them flea collars.
    • Eliminate fleas from your home.

    If traveling to parts of the world where outbreaks have occurred (Madagascar, Peru, Democratic Republic of Congo), check travel advisories before departure and bring plenty of insect repellent containing 80 percent DEET. There is currently no vaccine to prevent bubonic plague.

    The plague is one of several infectious diseases that were once universally fatal but can now be treated. While rare, it is important to take precautions to prevent this or any other flea-borne disease, whether it be typhus, tapeworm, or Lyme disease

    Sources:

    Centers for Disease Control and Prevention. "Plague: Resources for Clinicians." Atlanta, Georgia; updated October 15, 2015.

    New York Times. "Plague Is Found in New Mexico. Again." June 27, 2017.

    Sebbane, F.; Jarrett, C.; Gardener, D.; et al. "Role of the Yersinia pestis plasminogen activator in the incidence of distinct septicemic and bubonic forms of flea-borne plague." PNAS. 2006; 103(14); 5526-5530.

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