Which of the following transmit plague?

Fleas are the primary vector for transmitting plague. The disease caused by the bacterium Yersinia pestis is most commonly associated with fleas, specifically the Oriental rat flea, which infest rodents. When a flea bites an infected rodent, it can carry the bacteria and transmit it to other animals or humans through subsequent bites. This mode of transmission is crucial for the spread of the plague, especially in environments where rodent populations are present.

Understanding the life cycle and behavior of fleas helps clarify their role in plague transmission. When fleas ingest blood from infected hosts, the bacteria can multiply within the flea's gut. This leads to a blockage that causes the flea to regurgitate the infected material into the bite wound of another host, facilitating the transmission of the disease.

Other insects, such as sand flies, mosquitoes, and filth flies, do not play significant roles in the transmission of plague. Each has its unique diseases that they may transmit, but none are involved in the spread of plague as fleas are. This distinguishes the role of fleas in public health contexts and pest control strategies, emphasizing the need to manage rodent populations and flea infestations in order to prevent outbreaks of the plague.