Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/31/2003
Publication Date: 10/20/2003
Citation: TAPIA-PEREZ, G., GARCIA-VASQUEZ, Z., MONTALDO, H., GEORGE, J.E. INHERITANCE OF RESISTANCE TO FLUMETHRIN IN THE MEXICAN ALDAMASTRAIN OF THE CATTLE TICK BOOPHILUS MICROPLUS (ACARI:IXODIDAE). EXPERIMENTAL AND APPLIED ACAROLOGY. 2003. v. 31. p. 135-149. Interpretive Summary: Resistance of populations of the southern cattle tick, Boophilus microplus, to pesticides belonging to the pyrethroid chemical group is widespread in Mexico. Where resistance to pyrethroids occurs none of this group of chemicals is now useful for treating cattle to control the southern cattle tick. Other kinds of pesticides must now be employed in those locations. The mode of inheritance of resistance to the pyrethroid compound flumethrin was investigated in an effort to obtain information useful in the design of procedures for the control of ticks that would minimize the rate of selection for pyrethroid resistance in populations of the southern cattle tick in which resistance has not yet emerged. Results from a series of crosses between male and female ticks from a non-resistant susceptible tick strain and a resistant strain proved that more than one gene controlled the expression of resistance. The results from this investigation will facilitate additional research to determine the mechanism of resistance and to develop new methods for assessing the frequency of resistance genes in populations of the southern cattle that have been or are being exposed to flumethrin or other pyrethroid pesticides.
Technical Abstract: The objective of this study was to evaluate the inheritance mode of resistance to flumethrin in the Mexican Aldama Boophilus microplus strain. Two Mexican strains were used, the Chiapas susceptible (SS), and the Aldama flumethrin-resistant from Tamaulipas. Six steers weighing ca. 250 kg were randomly assigned for each of six crosses: the susceptible (SS), resistant (RR), and the F1 (RS, SR) reciprocal crosses and F2 (RS_RS and SR_SR). The reciprocal crosses were made to evaluate maternal and sex linkage effects. Bioassays tested resistant and susceptible larvae along with their hybrid F1 and F2 progeny against a series of concentrations of flumethrin (0, 0.0075, 0.00150, 0.00300, 0.00600 and 0.01200 mg/g). To test the single-gene hypothesis of resistance, a nonparametric line-cross test proposed by Collins was used. The bioassay data were subjected to probit analysis and the resistance factor and effective dominance obtained. Results of this study indicated that inheritance for flumethrin resistance in the Aldama strain was autosomal and controlled for more than one gene. The F1 and F2 larvae had similar lower resistant factor (RF 2.8-4.5) while the resistant Aldama strain was 21-fold higher (RF 81.8) than the mean of the F1 and F2. The extent of flumethrin resistance in the Aldama B. microplus strain depended upon the concentration of the pesticide used. Resistance was almost dominant at the lowest dose while almost completely recessive at the highest dose. Maternal effects were shown for egg-mass. These results shown here indicate more than one gene basis of flumethrin resistance in B. microplus ticks are present. Therefore it is necessary to locate and understand the major loci for elucidate the mechanism of resistance and improve the ability to track and delay the evolution of resistance.