Table 1.
Pyrethroid resistance in relation to pyrethroid use per country.
| Four categories of conditionsa | Number of eligible countries, by year | % per category | Pb | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Category | Confirmed resistance | Pyrethroids in use | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | 2019 | 2010–2014 | 2015–2019 | |
| 1 | Yes | Yes | 7 | 8 | 6 | 9 | 8 | 4 | 7 | 5 | 3 | 1 | 34.2% | 27.4% | n.s |
| 2 | Yes | No | 3 | 3 | 6 | 5 | 7 | 9 | 9 | 5 | 3 | 6 | 21.6% | 43.8% | 0.002 |
| 3 | No | Yes | 10 | 8 | 12 | 7 | 9 | 9 | 2 | 3 | 4 | 2 | 41.4% | 27.4% | 0.05 |
| 4 | No | No | 0 | 0 | 0 | 3 | 0 | 1 | 0 | 0 | 0 | 0 | 2.7% | 1.4% | n.s |
| Sum | 20 | 19 | 24 | 24 | 24 | 23 | 18 | 13 | 10 | 9 | 100.0% | 100.0% | |||
Presented is the number of eligible countries in each category per year. ‘Confirmed resistance’ refers to < 90% mortality of anophelines in insecticide susceptibility bioassays for pyrethroids24. ‘Pyrethroids in use’ refers to use in IRS for malaria control.
aCategories: 1, confirmed resistance, pyrethroids in use; 2, confirmed resistance, no pyrethroids in use; 3, no confirmed resistance, pyrethroids in use; 4, no confirmed resistance, no pyrethroids in use.
bχ2 test (df = 1) between the two periods for each category; n.s., not significant (P > 0.05).