A mechanical vector is a living thing that conveys a pathogen from one individual to the next, but is not essential for the reproduction and development of the pathogen. An example of a mechanical vector is a house fly that picks up salmonella bacteria on its feet and deposits the bacteria on an apple that is eaten by a human. Mechanical vectors are just one of several vector classifications.
Vectors are classified based on the manner in which they transport a microorganism and whether the microorganism replicates while present in or on the vector species. Mechanical vectors do not support replication, and they are generally very nonspecific to certain types of pathogens. For example, a fly may pick up any number of species of bacteria on its feet and deposit them on a human or his food.
Another type of vector is the intermediate host vector, which supports asexual replication of microorganisms. An example of an intermediate host vector is the tick, which supports replication of Borrelia burgdorferi bacteria that causes Lyme disease in humans and other mammals. A definitive host vector is capable of supporting sexual reproduction of the pathogen it hosts. An example is the mosquito, which serves as a vector for Plasmodium spp., the protozoan that causes malaria.