The reemergence of Aedes aegypti in Arizona.

Letters The Reemergence of Aedes aegypti in Arizona To the Editor: Aedes aegypti, primarily an urban, tropical mosquito, is a competent vector of dengue and yellow fever viruses. In the early 1900s, Ae. aegypti was found in every country in the Western Hemisphere except Canada. In the United States, repeated attempts to eradicate it have failed, and the mosquito is now well established in the southern states, from Texas to South Carolina, and more recently in Maryland and New Jersey (1,2). Although the arid landscape of southern Ari-zona is an unlikely habitat for Ae. aegypti, these mosquitoes were identified in the cities of Tucson between 1931 and 1946 (3,4) and Yuma in 1951 (5). Elsewhere in the western United States, Ae. aegypti has been conspicuously absent, except for periodic reports of populations in New Mexico during this same period (3,6). Beginning in 1969, the Arizona Department of Health Services initiated an arbovirus surveillance program involving state and local officials in routine monthly mosquito sampling between May and October of each year. Until 1994, no Ae. aegypti specimens had been identified in Arizona through routine surveillance, which involved adult collection with CO 2 and New Jersey light traps and larval dipping surveys, or through other mosquito research (7,8). In August 1994, a University of Arizona entomology professor reported finding several Ae. aegypti in his Tucson backyard. Followup surveys in September and October 1994 by state and county health officials identified a number of Ae. aegypti in that same neighborhood as well as in central Tucson. During September 1995, additional specimens were collected in Nogales and again in Tucson. The adult mosquitoes were collected with CO 2 traps in various locations in these two cities. In Tucson, trapping from four of five sites yielded 85 adult Ae. aegypti (8.5/trapnight). In Nogales, trapping from two of four sites yielded 122 adults (12.2/trapnight). Trapping done earlier in 1995 at these sites yielded no Ae. aegypti adults. Between 1994 and 1995, Ae. aegypti were trapped exclusively after the monsoon season (late July to early September), when late summer precipitation allowed for sufficient breeding conditions in backyards. However, in late March 1996, the Arizona Department of Health Services responded to a report of " ankle-biting " mosquitoes in central Tucson. Subsequently, two adult Ae. aegypti were trapped in the complainant's home. Since then, adult Ae. aegypti have been found in several new areas in and around …