Fleas are parasites that feed on the blood of any warm-blooded body. The most common species is the cat flea, which often feasts on cats, dogs and humans.
Each year, a few cases of bubonic plague are recorded in the United States, mostly in the Southwest. Humans typically contract the disease from the bites of infected fleas, or through skin abrasions that contact the blood of infected animals or the feces of infected fleas. The disease is typically carried by wild rodents, and transmitted to the fleas that bite them. The digestive system of an infected flea can become blocked by rapid reproduction of the bacteria, causing the flea to bite repeatedly in an attempt to avoid starvation.
Bubonic plague occurs most often where persons live or participate in outdoor activities in close proximity to wild rodents, such as rock squirrels, ground squirrels, prairie dogs, chipmunks and rats. Pets also bring plague-infected fleas into the home. Cats are highly susceptible to the disease. Outbreaks can arise in urban and rural areas, especially where conditions are primitive or unsanitary.
Symptoms of bubonic plague develop within one week of exposure to the bacterium, and may include headache, fever, weakness, fatigue and painful, swollen lymph nodes known as “buboes.” The disease responds well to antibiotics, but untreated persons may die within a week of showing symptoms.