Final answer:
A mechanical vector is a host that transfers a pathogen from one host to another without being infected itself. An example of a mechanical vector is a housefly.
Step-by-step explanation:
A mechanical vector is a host that transfers a pathogen from one host to another or from a reservoir to a host without being infected by the pathogen itself. An example of a mechanical vector is a housefly, which can carry disease-causing organisms on its body and transport them to humans or other animals. The housefly is not necessary for the life cycle of the infectious agent, but it plays a role in spreading the disease.