Which disease are several species of fleas known to efficiently vector?

Fleas are particularly well-known for being efficient vectors of the plague, specifically the bacterium Yersinia pestis, which causes this disease. When infected fleas bite mammals, including humans, they can transmit the bacteria into the bloodstream, leading to the severe clinical manifestations associated with plague.

This connection is historically significant, especially considering the role fleas played in the transmission of the plague during pandemics like the Black Death in the 14th century. Fleas live on rodents, which are common reservoirs for Yersinia pestis, and when these hosts die or are sick, fleas can jump to other mammals, facilitating the spread of the disease.

The other options presented—typhus, malaria, and dengue—are not efficiently transmitted by fleas. Typhus is generally associated with lice, while malaria is transmitted by Anopheles mosquitoes, and dengue is transmitted by Aedes mosquitoes. These distinctions clarify why plague is the correct response regarding effective flea vectoring.