[Human diffusion of arthropod disease vectors throughout the world]

The present distribution of animals and plants throughout the world is the result of an evolutionary process involving tectonic, climatic and biotic factors. Humans, since their appearance, have contributed to the spreading of many species including disease vectors and pests. When humans left their native African home, they brought with them ectoparasites such as lice and acarids. During the neolithic era, humans were leading domesticated animals which carried their own parasites into new areas. Dwelling commensals, flea, bugs, triatomids, flies, and cockroaches followed human migrations. In the second millennium, sailboats transported mosquito species which were resistant and reproduced on board, including Culex quinquefasciatus, Aedes aegypti, and Ae. albopictus. Steamers further shortened the length of trips and allowed the transport of anophelines. The opening of the Tamatave-Port-Louis line was immediately followed by the transport of An. gambiae from Madagascar to Mauritius and Reunion, and epidemics of malaria occurred on the two islands which had been free of the disease. Also, An. gambiae was transported from Senegal to Brazil. Old tires destined for recycling carried Ae. albopictus to the USA, Brazil, and then Italy. The pandemic of the plague at the end of the nineteenth century was propagated from harbour to harbour by steamers carrying both infected rats and their fleas Xenopsylla cheopsis. Aircrafts have reduced the travel time so much that in less than two days an insect could reach every point of the world. As soon as the airports had been built on the islands of French Polynesia, they were all colonized by Ae. aegypti. The same phenomenon occurred with midges (Fig. 2). Also, the construction of the airport on a Galapagos Island coincided with the importation of the blackfly Simulium bipunctatum from the continent. In addition, infected malaria mosquitos imported from tropical countries reached Europe and contaminated airport employees and local inhabitants. Six cases of malaria were recorded during the summer of 1994 around the Charles de Gaulle Airport, north of Paris, suggesting that the anophelines could have been imported from West and Central African countries which are served by this airport. The serious threat of vector importation is moderated by the vector's difficulty in adapting to new conditions. However any prediction is questionable.