Esterase profile in a pyrethroid-resistant Brazilian strain of the cattle tick Boophilus microplus (Acari, Ixodidae)

Abstract

The cattle tick Boophilus microplus causes great damage in livestock and is considered one of the most important tropical ectoparasites. The traditional method of control is based on the intensive use of pesticides, however the indiscriminate use of these compounds over the years has led to the selection of resistant ticks. Hydrolases, particularly esterases (EST), have been reported to be associated with acaricide resistance in B. microplus. We compared the esterase profile of susceptible and cypermethrin-resistant strains of adult B. microplus and a pyrethroid susceptible reference strain (the Mozzo strain) using polyacrylamide gel electrophoresis and specific staining. The electrophoretic profiles of protein extracts revealed the presence of four regions with esterase activity in the cypermethrin-resistant strain and three of these regions in the susceptible strains. The bands were numbered EST-1 to EST-4 in sequence (starting from the anode) according to their decrease in negative charge. The EST-1A and EST-1B enzymes were detected only in the resistant strain. The inhibition studies with eserine sulfate, copper sulfate, p-p-chloromercuribenzoate (pCMB), malathion and phenylmethylsulfonyl fluoride (PMSF) indicated that the EST-1A and EST-1B enzymes belong to the acetylcholinesterase class and are probably associated with resistance to acaricides in this Brazilian resistant strain of B. microplus.

Esterase mediated resistance in deltamethrin resistant reference tick colony of Rhipicephalus (Boophilus) microplus

“…Using copper sulphate, the intensity of all the esterase bands was similar to those observed in control without inhibitor, thus confirms the absence of arylesterases among the resolved bands. Although Baffi et al (2005) reported EST-3 as carboxylesterase after getting significant inhibition using both malathion and PMSF, in the present study, the staining intensity of EST-3 was inhibited using PMSF but was resistant to both malathion and eserine sulphate. Since EST-2 was inhibited by eserine sulphate, malathion and partially by TPP while EST-1 strongly by PMSF and partially by eserine sulphate and malathion both EST-1 and EST-2 were classified as acetylcholinesterase.…”

“…Among the bands detected in Tuxpan and Coatzacoalcos strains, the carboxylesterase, EST-9 and EST-10, respectively, were reported to be responsible for the Kunz and Kemp (1994), Jonsson and Hope (2007); Lovis et al (2013) development of resistance (Jamroz et al 2000). On the contrary, four esterase bands were found in cypermethrin and deltamethrin resistant adult ticks and three esterase bands in the susceptible adult ticks (Baffi et al 2005(Baffi et al , 2008. Similar profiles in resistant larval homogenate (IVRI-IV) were observed in the present study when stained with both anaphthyl and b-naphthyl acetate.…”

“…However, Baffi et al (2005) reported the inhibition of both EST-1 and EST-2 on application of eserine sulphate in cypermethrin-resistant Brazilian R. (B.)…”

“…(B.) microplus naturally exposed to multiple acaricides, Abdullah et al (2012) identified five esterase activity bands and were linked with deltamethrin resistance although the results had not been confirmed in reference homogenous deltamethrin resistant ticks as observed by Baffi et al (2005). The IVRI-IV colony was established by repeated selection of deltamethrin exposure for the last several years and nearly 40th generation having RF of 194.5 was used in the study.…”

The classification of esterases: an important gene family involved in insecticide resistance - A review

“…Four classes of esterases are distinguished using this scheme: (i) acetylesterases, which are not affected by any of the aforementioned inhibitors and have a preference for aliphatic substrates related to acetic acid, (ii) arylesterases, which are inhibited by sulphydryl reagents and have a preference for aromatic substrates, (iii) carboxylesterase, which are inhibited by organophosphorus compounds and have a preference for aliphatic esters (typically having a chain longer than acetic acid), and (iv) cholinesterases, which are simultaneously inhibited by OPs and eserine sulphate and have a preference for charged substrates (e.g., choline esters) instead of aliphatic and/or aromatic esters (Oakeshott et al 1993). As an alternative functional criterion beyond those proposed above, these inhibition tests for the biochemical characterisation of esterases have been used to classify a variety of esterases, including those in insects of the genera Culex, Drosophila (Healy et al 1991, Oakeshott et al 1993 and Aedes (Lima-Catelani et al 2004) as well as esterases of Arachnids, such as Rhipicephalus (Boophilus) microplus (Baffi et al 2005), and plants (Carvalho et al 2003).…”