Pyrethroid and organophosphate pesticide resistance in field populations of horn fly in Brazil

• Published in: Medical and veterinary entomology Vol. 33; no. 1; pp. 121 - 130
• Main Authors: Brito, L. G., Barbieri, F. S., Rocha, R. B., Santos, A. P. L., Silva, R. R., Ribeiro, E. S., Guerrero, F., Foil, L., Oliveira, M. C. S.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.03.2019; Wiley Subscription Services, Inc
• Subjects: acetylcholinesterase mutation; Animals; Bovidae; Brazil; Food contamination; Haematobia irritans; Insecticide Resistance - genetics; Insecticides - pharmacology; Livestock; Metabolites; Muscidae - drug effects; Muscidae - genetics; Mutation; Organophosphates; Organophosphates - pharmacology; Parasites; Pesticide resistance; Pesticides; Point mutation; Population studies; Pyrethrins - pharmacology; resistance mechanism; sodium channel; Sodium channels; Brazil; acetylcholinesterase mutation; resistance mechanism; sodium channel; Haematobia irritans
• ISSN: 0269-283X; 1365-2915
• DOI: 10.1111/mve.12330

Pesticides are used worldwide to control arthropod parasites in cattle herds. The indiscriminate and/or inappropriate use of pesticides without veterinary guidance is a reality in several countries of South America. Improper pesticide use increases the chances of contamination of food and the environment with chemical pesticides and their metabolites. Reduction of these contamination events is an increasing challenge for those involved in livestock production. The horn fly, Haematobia irritans (Linnaeus) (Diptera: Muscidae), is one of the most economically important parasites affecting cattle herds around the world. As such, horn fly control efforts are often required to promote the best productive performance of herds. Pesticide susceptibility bioassays revealed that pyrethroid resistance was widespread and reached high levels in horn fly populations in the Brazilian state of Rondônia. The knockdown resistance (kdr) sodium channel gene mutation was detected in all horn fly populations studied (n = 48), and the super kdr sodium channel gene mutation was found in all homozygous resistant kdr individuals (n = 204). Organophosphate resistance was not identified in any of the fly populations evaluated. The horn fly is one of the most economically important parasites affecting cattle herds around the world. Pesticide control in horn fly populations promotes excellent initial results, but the excessive use of these compounds results in insecticide resistance issues. The selection pressure imposed by pesticides means that as pesticide effectiveness increases, so do the selection for and rapidity of resistance development in horn fly populations.