Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 23, 1999
Publication Date: N/A
Interpretive Summary: Although the cattle fever tick (CFT) and the disease it transmits, babesiosis, were eradicated from the US after a 50-year eradication program of dipping cattle and temporarily vacating tick-infested pastures, these ticks are still widespread in Mexico and other parts of the Americas. Quarantine by vat dipping with chemical pesticides has prevented reinfestation in the US; however, CFT has developed resistance to such pesticides which means that the pesticides are not as effective as they once were. An understanding of the mechanisms of pesticide resistance can help develop a better pest management strategy and prolong the usefulness of the currently available pesticides. We have used sophisticated techniques of molecular biology to study one way the CFT might be developing pesticide resistance. This work will be very important to developing better methods for control of CFT and will help to protect US livestock from this serious tick pest and the disease it transmits.
Using reverse-transcription polymerase chain reaction (RT-PCR) and degenerate oligonucleotide primers derived from sodium channel sequences from other species, a cDNA sequence was amplified from the southern cattle tick, Boophilus microplus. The cDNA sequence has significant homology to the para-sodium channel gene from Drosophila and is located in domain II of fthe sodium channel, a region in which mutations have been identified that confer knockdown-resistance (kdr) to DDT and pyrethroids in insects. However, DNA sequence comparison between pyrethroid-resistant and pyrethroid-susceptible strains of the southern cattle tick shows no mutation in this region of the tick sodium channel gene homologue. This result indicates that the mechanism by which ticks develop the resistance to pyrethroids may differ from that in insects.