Aedes aegypti mosquitoes, which carry the pathogens responsible for dengue fever, Zika fever and other diseases, were first found in California in 2013. In a new PLOS Neglected Tropical Diseases study, the authors report that the insect immigrants were repeat offenders, entering the Golden State on at least two distinct occasions.
The researchers questioned if the Californian mosquitoes, now known to be present in at least 96 cities in the state, originated from a single or from multiple introductions. To find out, they examined the genetics of 586 A. aegypti mosquitoes from five northern and seven southern sites in California. They also looked at the genetics of A. aegypti from elsewhere in the southern U.S. and Mexico.
The scientists found that the A. aegypti mosquitoes in Northern California form a genetically distinct population from those in Southern California, and the two populations probably arose from at least two separate introductions occurring prior to 2013. The northern population, which is more genetically diverse than the southern one, likely entered from the South-Central U.S., while the southern population may have immigrated from Mexico or the Southwest U.S.
Since California has an unusually extensive mosquito-monitoring system, A. aegypti might well have invaded other U.S. states undetected. The researchers emphasize the importance of studying A. aegypti populations in disease prevention.
Image Credit: Evlyn Pless
Research Article: Pless E, Gloria-Soria A, Evans BR, Kramer V, Bolling BG, Tabachnick WJ, et al. (2017) Multiple introductions of the dengue vector, Aedes aegypti, into California. PLoS Negl Trop Dis 11(8): e0005718. https://doi.org/10.1371/journal.pntd.0005718
