Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 2, 1999
Publication Date: N/A
Interpretive Summary: Although the southern cattle tick (SCT) and the disease it transmits, babeosis, were eradicated from the U.S. after a 50-year eradication program of dipping cattle and temporarily vacating tick-infested pastures, they are still widespread in Mexico and other parts of the Americas. Quarantine by vat dipping with chemical pesticides has prevented reinfestation in the U.S. However, the SCT has developed resistance to such pesticides which means that it takes more and more of the pesticide to control the ticks. The way resistance is detected now is laborious and time consuming. Recent developments in molecular biology have made it possible to detect individual resistant insects, and we have done work on the SCT using similar molecular biology techniques. Our studies have shown that it will hopefully be possible to use these techniques to determine which ticks are resistant to pesticides and which are not. This will be of much value to researchers and others who are trying to protect the U.S. livestock industry from the SCT and the devastating disease it transmits.
Using a strategy based on degenerate primers derived from acetylcholinesterase (AChE) from other species, we cloned and sequenced a putative AChE cDNA from the southern cattle tick Boophilus microplus. The sequence has a high degree of homology to sequences of AChE from other species reported in the GenBank. It has an open reading frame of 1689 bp, corresponding to a deduced sequence of 563 amino acids. The cDNA sequence reported here has conserved regions and features shared by the AChE family, which are necessary for its catalytic activity. Complete sequences derived from organophosphorus acaricide resistant and susceptible strains were compared, but no differences were found. The results suggest that this putative AChE gene is not involved in resistance to organophosphorus compounds, as a mutated gene, in the resistant strain studied.