Identification of a point mutation in an esterase gene in different populations of the southern cattle tick, Boophilus microplus

Two esterase cDNA sequences were obtained from susceptible and organophosph orus resistant strains of Boophilus microplus. Both sequences have a high d egree of homology to carboxylesterase B. One gene has identical sequences i n both strains and the other showed two point mutations. One mutation produ ces an amino acid substitution when the amino acid sequence is deduced, thi s mutation was detected in six different populations susceptible and resist ant to insecticides, but a pyrethroid resistant strain was the only one tha t showed only the mutant allele. Identification of this mutation and the st rong signal detected in southern blot with this strain, suggest that estera ses are contributing to detoxification of pyrethroid compounds, as a resist ant mechanism in Mexican strains of the southern cattle tick. (C) 2000 Else vier Science Ltd. All rights reserved.