A “vector-borne disease” is one in which a pathogen (disease-causing microorganism) such as a bacteria, virus, protozoa or worm is transmitted from an infected animal or human host to a new, uninfected animal or human host by a vector (disease carrier). Generally, arthropods (invertebrate animals such as mosquitoes and ticks) are the most important vectors of human disease. However, vertebrate animals can also act as disease vectors – for example, mammals such as foxes, raccoons, skunks and bats can all transmit the Rabies virus to humans via a bite or scratch.
Arthropod vectors, such as mosquitoes and ticks, pick up pathogens from infected individuals (animals or humans) when they take a blood meal. The pathogens multiply within the arthropod vector’s body and then are transmitted to the next susceptible human or animal host during a subsequent blood meal.
Nearly half of the world's population is infected by vector-borne diseases resulting in high rates of morbidity (illness) and mortality (death). To date, the greatest impacts from vector-borne diseases such as Malaria, Dengue fever, Yellow fever and West Nile virus have been felt in developing countries located in tropical and subtropical areas. However, in recent years, there has been a significant increase in the transmission of vector-borne diseases such as West Nile virus and Lyme disease in more temperate regions including Europe and North America. Climate change, increased pesticide resistance, population growth, increasing urbanization, changes in agricultural practices, deforestation, limited surveillance resources and increased worldwide trade and travel may all be contributing factors to the continued spread of these and other vector-borne diseases in the future.
While some efforts to control vector-borne diseases have focused on control of specific pathogens through the development of human vaccines or the control of animal reservoirs (intermediate hosts) via vaccination or eradication of exposed populations, the most common control measures target the arthropod vectors via the use of personal protective measures, the elimination of arthropod breeding areas or the use of chemical or biological controls (pesticides) to kill the arthropod larvae or adults.