Characterization of permethrin-resistant Boophilus microplus (Acari: Ixodidae) collected from the state of Coahuila, Mexico.

Southern cattle ticks, Boophilus microplus (Canestrini) (Acari: Ixodidae), collected in Coahuila, Mexico, were determined to be resistant to permethrin. Discriminating concentration (DC) tests at the LC99 and 2X the LC99 of susceptible ticks produced 0 and 0.5% mortality, respectively, for permethrin. However, measured mortalities for coumaphos and amitraz acaricides were within the expected ranges. Polymerase chain reaction analysis of this strain detected a 99% frequency of homozygous resistant individuals in this strain.