ARS | Publication request: Multiple acetylcholinesterase genes expressed in the southern cattle tick, Rhipicephalus (Boophilus) microplus, a vector of bovine babesiosis and anaplasmosis

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 14, 2011
Publication Date: N/A

Technical Abstract: Cattle ticks of the genus Boophilus (now Rhipicephalus) were eradicated from the United States, but remain endemic in Central and South America, as well as portions of Africa, Asia, and Australia. Rhipicephalus (Boophilus) microplus and annulatus ticks present a continuing threat to the U.S. cattle industry because they vector pathogenic agents of bovine babesiosis and anaplasmosis, which may produce up to 90% mortality in naive cattle. Cattle imported into the U.S. are individually inspected and treated with acaricide to prevent reestablishment of "cattle fever ticks" within the U.S. A key component of the eradication program importation barrier is organophosphate (OP) acaricide, which is a quasi-irreversible inhibitor of acetylcholinesterase (AChE) in the tick central nervous system. Acaricide resistance is widespread, and production of OP-insensitive AChE is a major resistance mechanism in ticks. It has been shown that R. (B.) microplus expresses at least three different AChE genes in the tick synganglion (brain). The tick AChEs appear to functionally complement one another based on gene silencing studies. Multiple alleles for each of the three tick AChE transcripts are expressed in individual ticks, and each of the three known AChE genes are present in amplified copy number. The physiological roles of each tick AChE gene remain to be elucidated. Bioinformatic analysis of genomic and cDNA data from ticks suggests the presence of additional genes encoding AChE-like proteins. Vertebrates express multiple forms of AChE implicated in complex physiological, regulatory, and developmental processes, resulting from alternative splicing of a single AChE gene. The presence of multiple genes expressing significantly different AChEs in the tick likely reflects separation of structural and functional attributes associated with AChE in the vertebrate system, and may present an opportune model for experimental elucidation of the complex functions of vertebrate AChE. Consequently, there is great interest in establishing productive collaborations utilizing tick and vertebrate systems to elucidate the structural relationships and complex functions of acetylcholinesterase. USDA is an equal opportunity provider and employer