Resistance of the cattle tick Rhipicephalus (Boophilus) microplus to fluazuron in Argentina

TORRENTS J, SARLI M, SARMIENTO NF, ROSSNER MV, MOREL N, GUGLIELMONE AA, NAVA S.

EXPERIMENTAL AND APPLIED ACAROLOGY

SPRINGER

Lugar: Berlin; Año: 2022 vol. 86 p. 599 - 606

0168-8162

The aim of this work is to report the presence of resistance to fluazuron in a population ofRhipicephalus microplus in Argentina. The evidence was obtained from field and in vitrotrials. In the field trial, cattle infested with ticks was treated with two commercial formulationsof fluazuron. The in vitro trial (adult immersion test, AIT) was performed by usingtechnical grade fluazuron. In the field trial, there were no significant differences betweenthe treated and control groups between days 2 and 34 post-treatment. The only exceptions(treated group I in day 14 post-treatment, treated group II in days 23 and 29 post-treatment)had a significantly lower tick load than the untreated group, but the efficacy was not higherthan 70%. Viable engorged females were collected on both groups of treated bovines inall counts, and the production of viable larvae was not precluded with the application ofthe two commercial formulations of fluazuron evaluated in this study. The results obtainedwith the in vitro assay (AIT) also indicate that the R. microplus population tested in thiswork has a higher level of resistance to fluazuron than another susceptible field strain. Theintegrated analysis of the field and in vitro trials clearly reveals the emergence of resistanceto fluazuron in a R. microplus population from Argentina. This diagnosis of resistance doesnot imply that the fluazuron has lost its functionality at a regional scale, but it highlightsthe need to establish control strategies that minimize the use of this drug in order to preserveits functionality as an acaricide.