Answer:
The correct answer would be rickettsia
In biology, vector refers to the organisms which help in transporting the infectious agent or pathogen from one host to the another. Vector itself does not cause the disease but helps in spreading the disease.
Common vectors are species of mosquitoes, fleas, and ticks.
For example, rickettsia refers to the group of bacteria which cause typhus and other infections.
Ticks and mites serve as the vector for transportation or spreading of these bacteria. Bites of infected mite or tick can cause this infection.