Many types of research on arthropod-borne disease have been done during the past decades that have further our understanding of the processes by which arthropods vector diseases. By definition, a vector is an organism that introduces pathogens such as bacteria, viruses into another organism to cause an infection. Two basics mechanisms through which arthropods administer pathogens have been described, active transmission and passive transmission.
In the case of active transmission, also known as biological transmission, mostly seen in blood-feeding arthropods, the pathogen first passes part of its life cycle inside the arthropod vector before being transmitted. Different events could occur depending on the pathogen and its specific vector. The pathogen could rapidly increase its population through a series of multiplication within the vector. This would be the case of bacteria that replicate through binary division and thereby enhance the probability of its transmission in large number.
Another form of transmission involves the cyclical development of the infective agent to its mature form before being transmitted. Sometimes the pathogen undergoes both development and multiplication in the transmitting vector. This is the case of the malaria agent plasmodium, which undergoes cyclical changes and reproduces to increase its number inside the anopheles mosquito before transmission could occur. Arthropods could also vector diseases through a mechanical way. In this case, the disease agents are physically carried by the arthropod from one place or host to another. This mode of transmission is mostly observed in plant diseases, but also occurs in human and animal diseases. Sometimes the same pathogen is vectored by many arthropods vectors, and often the same vector could carry more than one pathogen thereby vectoring different diseases.