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THE REPORT "EMERGING VECTORS IN THE Culex pipiens complex" by D. M. Fonseca et al. (5 Mar., p. 1535) advances sweeping extrapolations concerning mosquito blood-feeding behavior and West Nile virus (WNV) transmission. These findings led Fonseca to conclude (1) that a European introduction of Nearctic mosquitoes could "radically change the dynamics of WNV in Europe" and to state "[t]his is a plea for more control of the movements of these disease vectors."
Fonseca et al. find that certain microsatellite markers distinguish Palearctic from Nearctic C. pipiens and interpret this observation as supporting the idea that the former feeds solely on birds and the latter indiscriminately on birds and mammals. Cited references (2, 3), however, permit no such suggestion, while other publications (4-13) indicate that Nearctic C. pipiens seek hosts no differently than do Palearctic forms. Their epidemiological interpretation of this analysis, therefore, is incorrect.
The most reasonable explanation for the relative severity of WNV in the United States rests on the novelty of the event and the pathogenicity of the introduced strain. Until recently, Nearctic birds remained nonimmune against this virus and had not adapted to its presence. In addition, other more effective vectors, such as C. tarsalis, transmit WNV in many intensely affected Nearctic sites (14). This report, therefore, fails to explain the unique features of the American WNV outbreak and cannot justify imposition of European quarantine measures against American mosquitoes.
A. SPIELMAN,1 T. G. ANDREADIS,2 C. S. APPERSON,3 A. J. CORNEL,4 J. F. DAY,5 J. D. EDMAN,4 D. FISH,6 L. C. HARRINGTON,7 A. E. KlSZEWSKI,1 R. LAMPMAN,8 C. C. LANZARO,4 F.-R. MATUSCHKA,9 L. E. MUNSTERMANN,6 R. S. NASCI,10 D. E. NORRIS,11 R.J. NOVAK,8 R. J. POLLACK,1 W. K. REISEN,4 P. REITER,12 H. M. SAVAGE,10 W. J. TABACHNICK,5 D. M. WESSON13
1 Harvard University, Boston, MA 02115, USA. 2 Connecticut Agriculture Experiment Station, New Haven, CT 06504, USA. 3 North Carolina State University, Raleigh, NC 27695, USA. 4 University of California, Davis, CA 95616, USA. University of Florida, Vero Beach, FL 32962, USA. 6 Yale University, New Haven, CT 06520, USA. 7 Cornell University, Ithaca, NY 14853, USA. 8 Illinois Natural History Survey, Champaign, IL 61820, USA. 9 Humboldt University, 10099 Berlin, Germany. 10 Centers for Disease Prevention and Control, Fort Collins, CO 80522,...