Acaricide resistance mechanisms in Rhipicephalus (Boophilus) microplus

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. (B.) 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.Keywords: Cattle tick, resistance mechanisms, target site mutation, metabolism. ResumoA resistência aos acaricidas tornou-se amplamente difundida nos países onde os carrapatos bovinos, Rhipicephalus (Boophilus) microplus, são um problema. A resistência surge por meio de alterações genéticas em uma população de carrapatos que causam modificações no local de ação, aumento do metabolismo ou sequestro do acaricida, ou ainda redução na capacidade do acaricida em penetrar através das camadas protetoras do corpo do carrapato. Neste artigo, foram revisados os mecanismos moleculares e bioquímicos da resistência aos acaricidas que ocorrem em R. (B.) microplus. A partir de um ponto de vista dos mecanismos envolvidos, a resistência aos piretróides tem sido caracterizada em maior grau do que em qualquer outra classe de acaricida. Embora uma grande quantidade de pesquisas têm sido direcionada para a descoberta de mecanismos que causam resistência aos organofosforados, muito pouco é conhecido ao nível molecular, e essa resistência parece ser mantida por intermédio de um processo multifatorial e complexo. Os mecanismos de resistência para os demais acaricidas são bem menos compreendidos. Os alvos de ação do fipronil e das lactonas macrocíclicas são conhecidos, e os estudos dos mecanismos de ação envolvidos estão ainda em estágios iniciais. O alvo de ação do amitraz ainda não foi definitivamente identificado, e isso é limitante aos estudos dos mecanismos envolvidos na resistência a esse acaricida.Palavras-chave: Carrapato bovino, mecanismos de resistência, mutação no local de ação, metabolismo.

Management of Cattle Ticks Rhipicephalus microplus (Acari: Ixodidae) in Response to the Emergence of Resistance to Synthetic Acaricides

“…These results were close to those obtained by Mendes et al (2011) who have proved that acaricides mainly pyrethroids and organophosphates were used for the control of ticks. The repeated use of chemicals for long periods and short intervals between treatments has favored the emergence of tick resistance especially the Rhipicephalus microplus species which have monotonic short cycle and which were much more prone to develop resistances mechanisms (Guerrero et al, 2012). The work carried out by Fernandez-Salas et al (2012) showed that 100% of breeders used acaricide as the main method of tick control.…”

Resistencia in vitro de la garrapata equina (Dermacentor nitens) en el departamento de Córdoba, Colombia

“…Los mecanismos que confieren la resistencia varían entre individuos, y los mejor descritos, hasta el momento, incluyen la insensibilidad en el sitio de acción, la resistencia metabólica y la disminución en la permeabilidad de la cutícula de la garrapata (ALONSO-DÍAZ et al, 2006;GUERRERO et al, 2012).…”

Genetic diversity, acaricide resistance status and evolutionary potential of a Rhipicephalus microplus population from a disease-controlled cattle farming area in South Africa

“…The principal mechanism of developing adaptive resistance in arthropods is via mutations in the acaricide target(s), rendering the target site(s) insensitive to the active compound (Chevillon et al, , 2007. Metabolic resistance can also arise via genetic changes within a tick population, resulting in increased metabolism or sequestration of the acaricide (Guerrero et al, 2012). In this regard, enzyme families involved in detoxification (or secondary metabolism) such as cytochrome P450's, esterases and glutathione S-transferases are generally up-regulated in metabolic resistance (Guerrero et al, 2012).…”

“…Metabolic resistance can also arise via genetic changes within a tick population, resulting in increased metabolism or sequestration of the acaricide (Guerrero et al, 2012). In this regard, enzyme families involved in detoxification (or secondary metabolism) such as cytochrome P450's, esterases and glutathione S-transferases are generally up-regulated in metabolic resistance (Guerrero et al, 2012).…”

“…An additional mutation at position 190 in the nucleotide sequence (C>A) results in an amino acid change from leucine to isoleucine that confers a moderate level of resistance to permethrin, cypermethrin and flumethrin (Morgan et al, 2009). The mutation in this domain has been shown to be present in the South African R. microplus population (Guerrero et al, 2012;van Wyk et al, 2015).…”