By Brian W. Donnelly, M.D., I.B.C.L.C., Pediatric Alliance — North Hills Division



Resurgence Of An Old Enemy”

An old microbial nemesis is making news once again in the United States. So far, there have been four fatalities from the plague this year. Since 2001, only a few cases of plague infecting humans have been reported by health officials (usually about three cases per year). In 2006, seventeen cases of plague were reported — the highest annual amount since 2001. We are up to 14 cases already this year. The reason for the increase is not clear.

If you are a student of history, you recall plague as the cause of the Black Death, which wiped out about half the population of Europe in the mid-1300’s. And, yes, rat fleas were the agents that spread Yersinia pestis, the bacteria that causes the dread disease.

The U.S. cases that have been investigated suggest some human contact with dead rodents. In fact, health officials in California have recently discovered the plague bacteria in the corpse of a squirrel in Lake Tahoe:

The Reno Gazette-Journal reports that the squirrel’s body was found in South Lake Tahoe in mid-August. El Dorado County Health Department officials say the test results came back Sep. 2.

Squirrel hunting season recently opened in California. El Dorado County employee Karen Bender says plague is naturally present in parts of California.


Prairie dog fleas have proven to be a fine haven for Y. pestis as well. And prairie dog populations in Arizona have been decimated as a result. Other animals known to harbor the plague bacteria include badgers, bobcats, coyotes and antelope.

The CDC summarizes some key facts about plague here, including these important clinical findings seen in infected people:

In humans, plague is characterized by the sudden onset of fever and malaise, which can be accompanied by abdominal pain, nausea, and vomiting. There are three main forms of plague, depending upon the route of infection. Bubonic plague, resulting from the bite of an infected flea, accounts for approximately 80%–85% of cases; patients develop a “bubo,” a painful swelling of one or several lymph nodes that progresses during the first few days of illness. Septicemic plague, accounting for approximately 10% of cases, can occur from a flea bite or from direct contact with infectious fluids; infection spreads directly through the bloodstream with no localizing signs. Primary pneumonic plague, occurring in approximately 3% of plague patients, results from aerosol exposure to infective droplets and is characterized by a fulminant primary pneumonia.

Plague can be treated with antibiotics, but the mortality rate is still around 16%. Untreated, the mortality rate is a disturbing 66% or higher.  Avoiding fleas is crucial for prevention. Applying insect repellent when wandering around endemic areas outdoors is a good idea. Flea collars for pets are useful. And extra care when handling or skinning wild animals is called for. Finally, children should be taught not to touch ill or dead animals, and to never feed squirrels, chipmunks, or other rodents.