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Everything Old Is New Again: Plague and Leprosy

By Ann Hohenhaus, DVMJuly 06, 2011
From the WebMD Archives

Last week there were two very interesting stories in the news about the intersection between people and animals. Both reported on diseases we rarely hear about anymore: plague and leprosy.

Leprosy is the older disease and has been reported since Biblical times. The first reported epidemic of plague occurred somewhat later, in the 6th or 7th century. Bubonic plague, or the Black Death, was the scourge of the Middle Ages.

Plague is an infectious disease caused by the bacteria Yesinia pestis. The usual source of Y. pestis is the rat flea, but hunting pets can contract the plague from eating infected rodents or rabbits. Even though Y. pestis is predominantly found in California, Utah, New Mexico, Arizona and Nevada, cases can be seen throughout the country if a human or pet travels to one of these areas and contracts the disease before they return home. An infected pet can, in turn, infect humans. The possibility of plague transmission is one reason prairie dogs may not make the best pets.

The name bubonic comes from the word bubo, which is a fancy word for enlarged lymph node. Wikipedia shows an illumination from a medieval Bible of sinners afflicted with buboes.

Both humans and pets with bubonic plague have enlarged lymph nodes, which are painful. Fever, malaise and non–specific flu-like symptoms are typical for plague in both humans and pets. Although last week’s plague case occurred in a dog, in general, cats are more susceptible to plague than dogs.

Leprosy was in the news too; not because of a sick dog or cat, but because of armadillos. Those prehistoric-looking armored mammals carry the leprosy bacteria, Mycobacterium leprae. Most leprosy cases occur outside the United States, but cases occur in people who have not traveled outside the USA. This finding puzzled researchers until the DNA of the M. leprae was studied. Both armadillos and humans infected with M. leprae in the USA share the same unique strain of the bacteria. This bacterium is different from the strain of M. leprae found outside the USA. The New England Journal of Medicine article concluded humans can contract leprosy from infected armadillos.

To help protect yourself and your pet from contracting diseases of wildlife:

  • Keep your pet leashed or indoors to prevent contact with wild animals which can cause serious diseases.
  • Never approach, pet or handle wildlife even if they are acting friendly.
  • If your pet is sick, always tell your veterinarian where your pet has traveled and do the same when you visit your physician. It may be just the perfect clue to the diagnosis.
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