Focal distribution of diflubenzuron resistance mutations in Culex pipiens mosquitoes from Northern Italy

• Published in: Acta tropica Vol. 193; pp. 106 - 112
• Main Authors: Porretta, D., Fotakis, E.A., Mastrantonio, V., Chaskopoulou, A., Michaelakis, A., Kioulos, I., Weill, M., Urbanelli, S., Vontas, J., Bellini, R.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.05.2019; Elsevier
• Subjects: Agriculture pest control; Biodiversity and Ecology; Chitin synthase; Environmental Sciences; Insect growth regulators; Insecticide resistance; Vector control; Insecticide resistance; Chitin synthase; Vector control; Agriculture pest control; Insect growth regulators
• ISSN: 0001-706X; 1873-6254
• DOI: 10.1016/j.actatropica.2019.02.024

Frequency of the diflubenzuron (DFB) susceptible and resistant alleles found in the Emilia-Romagna provinces (Italy) associated with DFB pressures from mosquito and orchard pest controls. [Display omitted] •Diflubenzuron resistant mutations occur in Italian populations of Culex pipiens, reaching over 70%.•Resistant allele frequencies increased from West to East of Emilia-Romagna region.•The intense insecticide pressure due to past agricultural applications, along with current mosquito control, can account for the observed pattern of focal resistance.•Ongoing Cx. pipiens resistance surveillance is of utmost importance to prevent its diffusion. Insecticide resistance is a major threat for vector control and prevention of mosquito borne diseases. In the Culex pipiens mosquitoes, resistance against diflubenzuron (DFB) was firstly detected in Ravenna (Emilia-Romagna region, Northern Italy), in 2015. The resistant phenotypes were associated with two mutations, I1043 M and I1043 L, at the amino acid 1043 of the chitin synthase gene. In this study, we monitored the presence, frequency and geographical distribution of the DFB resistant mutations in Cx. pipiens populations from Northern Italy, and in populations from Greece and France. In the Emilia-Romagna region, the resistant mutations were detected in 20 out of the 30 populations analysed, reaching allelic frequencies over 70%. The presence and distribution of the resistance mutations was highly focal, with a clear pattern of increasing resistant allelic frequencies moving from the Western towards the Eastern provinces of Emilia-Romagna. Contrary to Italy, DFB resistant alleles were not detected in the Cx. pipiens mosquitoes sampled from Greece and France. Following statistical, literature and bibliographical database analyses on the history of DFB insecticide use in the study areas, we suggest that the selection pressures from the intense agricultural DFB applications occurring throughout the’ 80-‘90 s against orchard pests, followed, from 2000s onwards by mosquito control DFB applications, may account for the high mutation frequencies observed in the Cx. pipiens populations of the Eastern provinces of Emilia-Romagna. The findings are of major concern for public health in Italy and Europe, as DFB remains a very important insecticide used for controlling arbovirus mosquito vectors, where alternative larvicides are extremely limited.