The bubonic plague was spread by which fleas?

• A. Mosquitoes
• B. Oriental rat fleas
• C. Dog fleas
• D. Cat fleas

Answer: (B)

Plague spreads to humans mainly through bites from fleas that have fed on infected rodents. The Oriental rat flea, Xenopsylla cheopis, is a classic and highly efficient vector in urban and port settings. When it feeds on an infected rat, Yersinia pestis travels into the flea, bacteria multiply and can block the flea’s gut. The blocked flea becomes ravenous and regurgitates the bacteria into the bite site, transmitting infection to a person. This makes the Oriental rat flea the best answer for how bubonic plague is spread. Other fleas can carry the bacteria in some circumstances, but mosquitoes do not transmit plague, and dog or cat fleas are not the primary vectors for bubonic plague in human outbreaks.