Origin of the Dengue Fever Mosquito, Aedes aegypti, in California.

Dengue fever is among the most widespread vector-borne infectious diseases. The primary vector of dengue is the Aedes aegypti mosquito. Ae. aegypti is prevalent in the tropics and sub-tropics and is closely associated with human habitats outside its native range of Africa. While long established in the southeastern United States of America where dengue is re-emerging, breeding populations have never been reported from California until the summer of 2013. Using 12 highly variable microsatellite loci and a database of reference populations, we have determined that the likely source of the California introduction is the southeastern United States, ruling out introductions from abroad, from the geographically closer Arizona or northern Mexico populations, or an accidental release from a research laboratory. The power to identify the origin of new introductions of invasive vectors of human disease relies heavily on the availability of a panel of reference populations. Our work demonstrates the importance of generating extensive reference databases of genetically fingerprinted human-disease vector populations to aid public health efforts to prevent the introduction and spread of vector-borne diseases. Author Summary: Dengue fever is a vector-borne disease that has dramatically increased in frequency and severity in recent decades, affecting over half of the world's population. The primary vector of dengue is Aedes aegypti. Breeding populations of this mosquito were reported for the first time in California in summer 2013, and the origin of these populations was unknown. We genotyped Ae. aegypti from California and compared their genetic composition and diversity against reference populations from Asia and the Americas, and with laboratory strains, to identify the source of this introduction. We identified the southeastern United States of America as the likeliest origin of California Ae. aegypti. This information will aid the design of containment, control, and elimination strategies to prevent the establishment of a permanent breeding vector population in the state. Note that the resolution achieved in tracking the origin of new disease-vector introductions is proportional to the completeness of the reference dataset. Our analysis was delayed to gather further data on regions close to California and would otherwise have been completed within a week. This work highlights the importance of having an extended dataset of human disease-vector genotypes in place prior to the occurrence of invasions that compromise public health. [ABSTRACT FROM AUTHOR]