Recent trends in global insecticide use for disease vector control and potential implications for resistance management

Abstract

Insecticides have played a major role in the prevention, control, and elimination of vector-borne diseases, but insecticide resistance threatens the efficacy of available vector control tools. A global survey was conducted to investigate vector control insecticide use from 2010 to 2019. Out of 140 countries selected as sample for the study, 87 countries responded. Also, data on ex-factory deliveries of insecticide-treated nets (ITNs) were analyzed. Insecticide operational use was highest for control of malaria, followed by dengue, leishmaniasis and Chagas disease. Vector control relied on few insecticide classes with pyrethroids the most used overall. Results indicated that IRS programs have been slow to react to detection of pyrethroid resistance, while proactive resistance management using insecticides with unrelated modes of action was generally weak. The intensive use of recently introduced insecticide products raised concern about product stewardship regarding the preservation of insecticide susceptibility in vector populations. Resistance management was weakest for control of dengue, leishmaniasis or Chagas disease. Therefore, it will be vital that vector control programs coordinate on insecticide procurement, planning, implementation, resistance monitoring, and capacity building. Moreover, increased consideration should be given to alternative vector control tools that prevent the development of insecticide resistance.

Figure 1

Map showing targeted and responding countries. The boundaries and names shown, and the designations used on this map do not imply the expression of any opinion whatsoever on the part of the World Health Organization concerning the legal status of any country, territory, city, or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. Dotted lines on maps represent approximate border lines for which there may not yet be full agreement. Data source: World Health Organization (WHO). Map production: Control of Neglected Tropical Diseases, WHO. ^©WHO 2021. All rights reserved. Written permission to use and adapt the map was granted by WHO.

Figure 2

Area graph of global use of vector control insecticides by intervention type. Results are pooled for the four selected diseases and are expressed in standard spray coverage.

Figure 3

Area graph of vector control insecticide use by insecticide class. (a) African Region, (b) Asia–Pacific Region plus Latin American & Caribbean Region combined. Results are pooled for the four selected diseases and expressed in standard spray coverage. Striped pattern indicates use of insecticides in ITNs; non-striped pattern indicates use in spraying operations (i.e., residual spraying, space spraying, larviciding). Shades of blue or shades of red indicate insecticide sub-groups within a mode of action. ‘Other classes’ represent bacterial larvicides, insect growth regulators, spinosyns, and pyrroles.

Figure 4

Area graph of vector control insecticide use, excluding use in ITNs, by disease. Results are presented for three geopolitical regions, (a–c) for control of malaria, (d–f) dengue, (g–i) leishmaniasis, and (j–l) Chagas disease, and expressed in standard spray coverage. Shades of blue or shades of red indicate insecticide sub-groups within a mode of action. ‘Other classes’ represent bacterial larvicides, insect growth regulators and spinosyns (all used as larvicides).