ARS | Publication request: MOLECULAR AND BIOCHEMICAL DIAGNOSIS OF ESTERASE-MEDIATED PYRETHROID RESISTANCE IN A MEXICAN STRAIN OF BOOPHILUS MICROPLUS (ACARI: IXODIDAE)

Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 2003
Publication Date: December 31, 2002
Citation: GUERRERO, F., PRUETT JR., J.H., LI, A.Y. MOLECULAR AND BIOCHEMICAL DIAGNOSIS OF ESTERASE-MEDICATED PYRETHROID RESISTANCE IN A MEXICAN STRAIN OF BOOPHILUS MICROPLUS (ACARI:IXODIDAE). EXPERIMENTAL AND APPLIED ACAROLOGY. 2002. v. 28. p. 257-264.

Interpretive Summary: We examined pyrethroid resistant Mexican strains of Boophilus microplus using biochemical and molecular tests to determine the mechanisms conferring resistance. One biochemical test that we used examined each strain's ability to biochemically degrade permethrin while a second test examined the abundance and variety of detoxifying enzymes called esterases in each strain. Permethrin degradation assays and esterase activity gel assays indicated enhanced esterase-mediated metabolic detoxification in the Cz strain, while two other pyrethroid resistant strains, Co and SF, and the control susceptible strain had lower levels of permethrin degradation capability. The sodium channel protein is the target of pyrethroid pesticides and we have developed a DNA-based assay to detect a pyrethroid target site resistance-associated mutation in the tick sodium channel gene. Results from these assays found only low levels of gene mutations in the sodium channel gene from ticks of the Cz strain while the Co and SF strains had high levels of the mutated sodium channel alleles. In summarizing the results from the resistance mechanism assays, the Co and SF strains appear to use the mutated sodium channel target site resistance mechanism, while the Cz strain uses a metabolic detoxification mechanism. A specific esterase, designated CzEst9, believed to be responsible for the esterase-mediated pyrethroid resistance in the Cz strain was purified, the gene encoding CzEst9 cloned and recombinant protein expressed in bacterial cells.

Technical Abstract: We examined pyrethroid resistant Mexican strains of B. microplus using biochemical and molecular tests to determine the mechanisms conferring resistance. Permethrin hydrolysis assays and esterase activity gels indicated enhanced esterase-mediated metabolic detoxification in the Cz strain, while two other pyrethroid resistant strains, Co and SF, and the control susceptible strain had lower levels of permethrin hydrolysis. Results from assays using a PCR-based test to detect a pyrethroid target site resistance-associated mutation in the tick sodium channel gene found only low levels of mutations in the Cz strain while the Co and SF strains had high levels of the mutated sodium channel alleles. A specific esterase, designated CzEst9, believed to be responsible for the esterase-mediated pyrethroid resistance in the Cz strain was purified, the gene encoding CzEst9 cloned and recombinant protein expressed in bacterial cells