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Title: Acaricide resistance mechanisms in Rhipicephalus microplus

Author
item Guerrero, Felicito
item LOVIS, LÉONORE - Neuchatel University - Switzerland
item MARTINS, JOÃO - Desiderio Finamore Veterinary Research Institute (FEPAGRO)

Submitted to: Brazilian Journal of Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2012
Publication Date: 4/1/2012
Citation: Guerrero, F., Lovis, L., Martins, J. 2012. Acaricide resistance mechanisms in Rhipicephalus microplus. Brazilian Journal of Veterinary Parasitology. 21(1):1-6.

Interpretive Summary: Cattle ticks are a major problem for cattle producers in most of the temperate and tropical countries of the world. The economic damage they cause is such that tick control is necessary; this is accomplished primarily by acaricide usage. Unfortunately, acaricide resistance has become widespread in the cattle tick, Rhipicephalus (Boophilus) microplus. Resistance arises through genetic changes in a cattle tick population that causes modifications to the target site, increased metabolism or sequestration of the acaricide, or reduced ability of the acaricide to penetrate through the outer protective layers of the tick's body. We review the molecular and biochemical mechanisms of acaricide resistance that have been shown to be significant in R. microplus. Resistance to pyrethroids has been characterized to a greater degree than any other acaricide class. Although a great deal of research has gone into discovery of the mechanisms that cause organophosphate resistance, very little is defined at the molecular level and organophosphate resistance seems to be a complex and multifactorial process. The resistance mechanisms for other acaricides are less well understood. The target sites of fipronil and the macrocyclic lactones are known and resistance mechanism studies are in the early stages. The target site of amitraz has not been definitively identified and this is hampering mechanistic studies on this acaricide.

Technical Abstract: Acaricide resistance has become widespread in countries where cattle ticks, Rhipicephalus (Boophilus) microplus, are a problem. Resistance arises through genetic changes in a cattle tick population that causes modifications to the target site, increased metabolism or sequestration of the acaricide, or reduced ability of the acaricide to penetrate through the outer protective layers of the tick's body. We review the molecular and biochemical mechanisms of acaricide resistance that have been shown to be functional in R. microplus. From a mechanistic point of view, resistance to pyrethroids has been characterized to a greater degree than any other acaricide class. Although a great deal of research has gone into discovery of the mechanisms that cause organophosphate resistance, very little is defined at the molecular level and organophosphate resistance seems to be maintained through a complex and multifactorial process. The resistance mechanisms for other acaricides are less well understood. The target sites of fipronil and the macrocyclic lactones are known and resistance mechanism studies are in the early stages. The target site of amitraz has not been definitively identified and this is hampering mechanistic studies on this acaricide.