Submitted to: Acarology International Congress Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 4/27/2010
Publication Date: 8/23/2010
Citation: Miller, R. 2010. Past, Present, and Future of Chemical Acaricides. Acarology International Congress Proceedings. 1:155.
Technical Abstract: There have been many different acaricides and acaricide formulations used throughout the history of tick control. Originally, various mixtures of crude oil, lard, sulfur, and kerosene were used for dipping livestock. This was followed by Beaumont crude oil. Arsenical dips were introduced in 1911 and used for 56 years in the United States. Organophosphate (OP) acaricides replaced arsenical dips in 1967, and are still used today. Amitraz was introduced to control OP-resistant ticks at the same time the pyrethroids were introduced in 1986, but its use was initially limited due to higher cost. The use of amitraz became more frequent after 1993 when pyrethroid resistance problems started to hinder tick control efforts. Macrocyclic lactones (ML), such as moxidectin and ivermectin, are known to possess broad spectrum activity against both internal and external parasites of host animals. The development of multiple resistance to OPs, pyrethroids, and amitraz prompted the search for alternative acaricides with different mode of action for tick control in Australia, Argentina, Brazil and Mexico. The first case of resistance to ML was reported from Brazil in 2001, and a more recent study in 2006 using the larval immersion test (LIT) confirmed the existence of 3.8-fold resistance to ivermectin in a tick strain from the state of Sao Paulo, Brazil. Fipronil, spinosad, and fluazuron are three new products available for tick control, but resistance and suboptimal control have made their use limited. Piperonyl butoxide (PBO) is the only synergist that has been used with pyrethroid acaricides to control pyrethroid-resistant ticks, and no synergist has been available for OPs. Several chemical compounds have recently been identified as having the potential to be used as synergists for OPs and amitraz, particularly coumaphos, to control OP-resistant ticks. Acaricide mixtures as a resistance management strategy have also been explored. Results of a recent study revealed synergism between permethrin and amitraz. Permethrin-amitraz mixtures have the potential to control tick populations resistant to pyrethroids, amitraz, or both. Anti-tick compounds synthesized by plants (especially from Brazil and Africa) fungi, and bacteria are being studied as potential new tick control products. Advances in genomics have led to the possibility for mining tick genomes for potential new acaricidal targets. These targets can be manipulated by either designing specific chemicals that have the ability to fit into specific receptors or breakdown gene products or, alternatively, with anti-tick vaccines developed to target these sites with antibodies created by the host.