Which disease is transmitted to humans primarily by the Oriental rat flea and can present in bubonic or pneumonic forms?

• A. Plague
• B. Murine typhus fever
• C. Rickettsial pox
• D. Dermatitis

Answer: (A)

Plague is a flea-borne disease caused by Yersinia pestis that is classically transmitted to humans by the Oriental rat flea. It can present in two major forms: bubonic plague, with painful swollen lymph nodes (buboes) and systemic symptoms after a flea bite; and pneumonic plague, where the infection involves the lungs and can spread between people via respiratory droplets, making it especially dangerous. The Oriental rat flea is the classic vector linked to rats carrying the bacterium. Other flea-borne illnesses, like murine typhus, are caused by different pathogens and don’t characteristically cause buboes or primary pneumonic disease, and dermatitis is not a systemic flea-borne illness. Therefore, the described disease is plague.