Saturday, 17 February 2018

First report of the effect of Ocotea elegans essential oil on Rhipicephalus (Boophilus) microplus

Veterinary Parasitology Available online 7 February 2018 In Press, Accepted ManuscriptWhat are Accepted Manuscript articles? Veterinary Parasitology Author links open overlay panelAmandaFigueiredoaLeonor M.NascimentobLouyse G.LopescRodrigoGigliotiaRicardo D.D.G.AlbuquerquebMarcelo G.SantosdDeborah Q.FalcãoeJeane A.P.NogueirabLeandroRochabeAna Carolina S.Chagasf a Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP), Jaboticabal, São Paulo, Brazil b Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Rio de Janeiro, Brazil c Centro Universitário Central Paulista (UNICEP), São Carlos, São Paulo, Brazil d Universidade do Estado do Rio de Janeiro (UERJ), São Gonçalo, Rio de Janeiro, Brazil e Universidade Federal Fluminense (UFF), Niterói, Rio de Janeiro, Brazil f Embrapa Pecuária Sudeste (CPPSE), São Carlos, São Paulo, Brazil Received 6 December 2017, Revised 5 February 2018, Accepted 6 February 2018, Available online 7 February 2018. Get rights and content Highlights • Tick resistance to synthetic acaricides is a major concern, justifying the search for new bioactive compounds. • The acaricidal and repellent effect of the Ocotea elegans essential oil on R. (B.) microplus were evaluated. • The chemical analysis of the essential oil from leaves revealed 92.2% sesquirosefuran. • Larval repellency and acaricidal effects higher than 90% were obtained at low concentrations. ABSTRACT Rhipicephalus (Boophilus) microplus is responsible for reducing animal welfare, causing a drop in productive performance and transmitting hemoparasites. The main strategy of tick control is application of synthetic acaricides. However, parasite resistance to these compounds is a major concern. Therefore, the acaricidal and repellent in vitro effect of the Ocotea elegans essential oil on larvae and adult females of R. (B.) microplus were evaluated. The larval packet test (LPT), larval repellency test (RT) and adult immersion test (AIT) were performed. The essential oil was analyzed by gas chromatography (GC/FID) and the structure of the oil’s major constituent (92.2% sesquirosefuran) was elucidated by nuclear magnetic resonance. In the AIT, efficacy higher than 90% was detected from the concentration 25 mg/mL upward. In both LPTs performed after 48 h, only the 100 mg/mL concentration resulted in mortalities above 70%. On the other hand, the essential oil caused an average of 95.8% repellency from 0.78 to 100 mg/mL. The LC50 in the two LPT (48 h) tests were 59.68 and 25.59 mg/mL, respectively. The LC50 and LC90 in the AIT were 4.96 and 17.37 mg/mL, and in the RT they were 0.04 and 1.24 mg/mL respectively. We conclude that the essential oil of O. elegans leaves has a significant acaricidal effect on engorged females and on larval repellency of R. (B.) microplus ticks, and can be a promising alternative for the control of this ectoparasite. Graphical abstract Download high-res image (169KB)Download full-size image Keywords cattle tick resistance alternative control repellency sesquirosefuran