First case reported of amitraz resistance in the cattle tick boophilus microplus in mexico

Abstract

The objective of this study was to document the first case in Mexico of Amitraz resistance in B. microplus ticks. A sample of B. microplus ticks was obtained in the municipality of Emiliano Zapata, Tabasco, where there had been reports of lack of control with this ixodicide. The tick strain was named ",,San Alfonso",, and (F 1 ) larvae were used from the parental generation of adult engorged females. These were tested with a discriminate dose of Amitraz 0.0002%, (Taktic®) in a emulsifiable concentrated formulation. Modified larval immersion test were used, with a 72 hr exposition time. Abeerden Angus bovines were infested with the F1 larvae generation in order to obtain adult female ticks, that were then tested by adult immersion test with commercial formulas used in Mexico such as: Taktic®, Bovithion®, Dursban®, Esteladon®, Asuntol®, Bayticol®, Permetrin, Batestan®, Ectogan® and Garraban®, using the commercially recommended concentration during a 1 min exposition. The results showed that in the larvae tmortality percentage with Amitraz was 25.3% and the resistance index was 41.9. The ",,San Alfonso",, B. microplus strain also showed resistance to organophosphates and pyrethroids. The percentage of control obtained by Amitraz in the adult phase was 22.8%. According to these findings it was determined that the ",,San Alfonso",, strain is the first case in Mexico of Amitraz resistance in the B. microplus cattle tick.