Definition of vector

In ancient times, insects were very important in the transmission of communicable diseases. The definition of vector was then related mostly to insects. Later on the term vector has been used more widely to include other non-human animals including snails, dogs and rats. Alternative definitions are found. For example, vectors can be defined as:

arthropods and other invertebrates which transmit infection by inoculation into or through the skin or mucous membrane by biting or by deposit of infective materials on the skin or on food or other objects.

This classical definition considers mainly the arthropods (which include insects and other organisms such as mites). It shows the mechanisms of transmission as inoculation (biting) and depositing infective materials (pathogenic organisms such as bacteria) on skin and food.

Vectors can also be defined as any non-human carriers of pathogenic organisms that can transmit these organisms directly to humans. Vertebrates, such as dogs and rodents, and invertebrates, such as insects, can all be vectors of disease.

This second definition focuses on the range of living things involved. Knowing this definition is helpful in the design of preventive measures for controlling living organisms such as insects and rats which carry the disease agent (bacteria, virus) from an infected person to a healthy person.