Question

There is an outbreak of buboes in a community. What is the vector?

• A. Xenopsylla (Rat Flea)
• B. Tse tse fly
• C. Human flea
• D. Sand fly

Hint:

Buboes are the hallmark of plague caused by Yersinia pestis; think about which rodent flea transmits this disease.

Answer 1

The Correct Option is A

Step 1: Define buboes. A bubo is an inflamed, swollen lymph node, particularly in the inguinal or axillary region. An outbreak of buboes in a community is the classic presentation of bubonic plague, caused by Yersinia pestis.

Step 2: Identify the transmission cycle. Plague is a zoonotic disease. Rats are the primary reservoir. The vector that transmits Yersinia pestis from infected rats to humans is the Xenopsylla cheopis (Oriental rat flea). When a rat dies, its fleas seek a new host and may bite humans, regurgitating the bacteria during the blood meal.

Step 3: Eliminate wrong options.

• Tsetse fly -- transmits Trypanosoma brucei (sleeping sickness)
• Human flea (Pulex irritans) -- can transmit plague in rare circumstances but is NOT the primary vector
• Sand fly -- transmits Leishmania species

Step 4: Epidemiological significance. When infected rat fleas bite humans, Yersinia pestis enters the lymphatics, causing massive lymph node enlargement (bubo). If untreated, bacteraemia and septicaemia follow, with >50% mortality.

Step 5: Conclusion. Xenopsylla cheopis (rat flea) is the primary vector of bubonic plague.