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United States Department of Agriculture

Agricultural Research Service

Title: Use of An Allele-Specific Polymerase Chain Reaction Assay to Genotype Pyrethroid Resistant Strains of Boophilus Microplus (Acari:ixodidae)

Authors
item Guerrero, Felix
item Davey, Ronald
item Miller, Robert

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 15, 2000
Publication Date: N/A

Interpretive Summary: A PCR-based assay has been developed to detect the presence of a pyrethroid resistance-associated amino acid substitution in the DNA of the cattle fever tick,Boophilus microplus. The assay utilizes a simple method for the extraction of DNA from individual tick larvae and tests individuals for the presence of an amino acid substitution in a segment of the sodium channel gene coding region which has been shown to be mutated in other pyrethroid resistant arthropods. The sodium channel is the target site of pyrethroid pesticides and amino acid substitutions in the coding region are a likely cause of target site-mediated pyrethroid resistance in ticks. Using the new PCR assay, several strains of B. microplus derived from outbreaks in Mexico and the Texas-Mexico border were evaluated. High frequencies of this amino acid substitution were found in the Corrales and San Felipe strains of ticks which bioassay methods had previously shown to possess target site insensitivity mechanisms for pyrethroid resistance. The Caporal Resistant strain contained a lower yet substantial number of amino acid-substituted alleles. Very low amino acid substitution frequencies were found in the susceptible reference Gonzales strain and the Coatzacoalcos strain which has metabolic esterase-mediated pyrethroid resistance. The amino acid substitution was not found in 6 other strains which were susceptible to pyrethroids. The PCR assay described in this research can yield results within a few hours of receiving an individual tick while the most commonly used bioassay procedures often require large numbers of larvae and often several weeks can elapse before results are available.

Technical Abstract: A PCR-based assay has been developed to detect the presence of a pyrethroid resistance-associated amino acid substitution in Boophilus microplus. The assay utilizes a simple method for the extraction of genomic DNA from individual larvae and genotypes individuals for the presence of a Phe to Ile amino acid substitution in the S6 transmembrane segment of domain III of the para-like sodium channel, clearly distinguishing heterozygotes from homozygotes. High frequencies for this amino acid substitution were found in the Corrales and San Felipe strains which have target site insensitivity mechanisms for pyrethroid resistance. The Caporal Resistant strain contained lower yet substantial number of amino acid-substituted alleles. Very low amino acid substitution frequencies were found in the susceptible reference Gonzales strain and the Coatzacoalcos strain which has metabolic esterase-mediated pyrethroid resistance. The amino acid substitution was not found in 6 other strains which were susceptible to pyrethroids.

Last Modified: 8/21/2014
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