Which vector is most efficient at carrying plague, typhus, and tularemia?

Fleas are the most efficient vectors for carrying plague, typhus, and tularemia due to their biology and ecological associations. The plague, caused by the bacterium Yersinia pestis, is primarily transmitted through fleas that infest rodents, particularly rats. When a flea bites an infected rodent, it can become infected and later transmit the bacterium to humans through their bites.

Typhus, particularly murine typhus, is also associated with fleas, as it is commonly transmitted by the fleas that infest rats, which can act as reservoirs for the disease. Tularemia, caused by the bacterium Francisella tularensis, can be transmitted by various vectors, including fleas, although other vectors like ticks and deer flies also play a role.

Fleas are particularly adept at maintaining these pathogens due to their feeding habits, which involve repeated blood meals from host animals. This behavior ensures they can efficiently spread pathogens from one host to another, making them a significant vector for these infectious diseases. Other options, such as mosquitoes or ticks, while involved in disease transmission, are not the primary vectors for all three diseases listed.