Modification of the Food and Agriculture Organization Larval Packet Test to Measure Amitraz-Susceptibility Against Ixodidae

Abstract

Modifications of exposure time, substrate, and formulation were made to the Food and Agriculture Organization Larval Packet Test (LPT) to determine a combination suitable for measuring the susceptibility of Boophilus microplus (Canestrini) to amitraz. Exposure time influenced the slope of the dose-response when paper was used as a substrate for amitraz. However, time did not influence the dose-response slope when nylon fabric was used as an amitraz substrate. Formulated amitraz produced results with less deviation from the log-probit model than technical amitraz. The combination of formulated amitraz and nylon fabric as a substrate for amitraz produced results that best fit the log-probit model. The modified FAO procedure (formulated amitraz/nylon substrate combination) was used to assay a Brazilian strain of B. microplus and a Panamanian strain of Rhipicephalus sanguineus (Latreille). Resistance ratios (95% CI) of 26.3 (25.7-26.9) and 7.3 (5.5-9.9) were calculated for the B. microplus and R. sanguineus strains, respectively. A discriminating dose of 0.03% amitraz was determined for B. microplus. This technique will help to locate amitraz resistant tick populations, provide data for improved control practices, and aid in the discovery of resistance mechanisms through synergist studies and verification of molecular techniques.

Comparison of three larval bioassays to evaluate susceptibility of Rhipicephalus (Boophilus) microplus to amitraz

“…The LPT was modified for amitraz by Miller et al (2002), and this test has been recognized and accepted by the UN Food and Agriculture Organization (FAO, 2004) for diagnosing resistance to amitraz. For this reason, it was used as the reference test in this study.…”

“…The LPT was performed as described by Miller et al (2002). Amitraz was dissolved at 1% in a solution composed of two parts of trichloroethylene and one part of olive oil (TCE-OO).…”

“…(B.) microplus can be diagnosed using the larval stage in in vitro bioassays: a) larval packet test (LPT), originally described by Stone and Haydock (1962), standardized by FAO (1971) and then modified by Miller et al (2002), with the aim of specifically diagnosing amitraz resistance; b) larval immersion test (LIT), originally described by Shaw (1966), then adapted for microcentrifuge tubes by Sabatini et al (2001) and used successfully for diagnosing resistance to ivermectin (KLAFKE et al 2006(KLAFKE et al , 2012 and fipronil (CASTRO-JANER et al, 2010); and c) syringe immersion test (SIT), described by Souza et al (2008) although not yet standardized for routine use as an acaricide resistance diagnostic tool. Recently, Mendes et al (2013) described the use of LIT for diagnosing amitraz resistance in R.…”

Proposta para teste carrapaticida por imersão de larvas de Rhipicephalus (Boophilus) microplus: avaliação em cipermetrina e amitraz

“…Em função disso, os pesquisadores têm se preocupado em aprimorar as técni-cas de diagnóstico da resistência. Exemplos destas novas metodologias é a modificação da técnica do pacote de larvas (LPT), publicada por Miller et al (2002) A realização do presente trabalho teve como objetivo desenvolver uma técnica de avaliação de carrapaticidas por imersão de larvas.…”

Molecular Modeling, Structural Analysis and Evaluation of 1-Deoxy-D-Xylulose-5-Phosphate Reductoisomerase (DXR) as a Putative Drug Target For Theileria Parva

“…In general, the ECF therapy is based on controlling strategies that utilize acaricides for tick vector (4) immunization via the live attenuated cell-line vaccine (5) and the medical consensus that combines drugs such as parvaquone and buparvaquone (6,7) for Theileria parva. On the other hand, the factors limiting the wide use of this treatment are the high costs of the acaricides that are utilized for tick control (8) and the rapid resistance development against a wide variety of these (9,10), as well as the absence of an efficient vaccine against T. parva that is proven to be safe (4). Moreover, in 2010, resistance to buparvaquone has been observed as well (11); this was followed by a new report in the year 2012 caused by point mutation mitochondrial cytochrome b gene in the parasite (12,13).…”