Knockdown resistance in pyrethroid-resistant horn fy (Diptera: Muscidae) populations in Brazil.

To investigate the kdr (knockdown resistance) resistance-associated gene mutation and determine its frequency in pyrethroid-resistant horn fy (Haematobia irritans) populations, a total of 1,804 horn flies of 37 different populations from all Brazilian regions (North, Northeast, Central-West, Southeast, and South) were molecular screened through polymerase chain reaction (PCR). The kdr gene was not detected in 87.08% of the flies.