Effects of acaricidal essential oils from Lippia sidoides and Lippia gracilis and their main components on vitellogenesis in Rhipicephalus microplus (Canestrini, 1888) (Acari: Ixodidae).

Rhipicephalus microplus is an important cattle tick, and resistant strains to synthetic compounds have been widespread. The combined effects of different essential oil compounds enhance biological activity and reduce selection for the development of target organism resistance. Essential oils of two different genotypes of each of Lippia sidoides and Lippia gracilis and their main components, the isomers thymol and carvacrol, have acted as acaricides against R. microplus. Little is known about the effects of the essential oils of L. sidoides and L. gracilis and thymol and carvacrol on the morphophysiology of R. microplus ovaries. This study aimed to identify the morphological changes in the ovaries of R. microplus females treated with essential oils from two different genotypes of each of L. sidoides (102 and 103) and L. gracilis (106 and 201) and the terpenes thymol and carvacrol through histological techniques. The LC50 and LC75 of essential oils and thymol and carvacrol were used for Adult Immersion Test (AIT) with groups of five fully engorged females of R. microplus. A negative control (DMSO 3% solution) was performed. Seven days after the AIT, the ticks were dissected to collect ovaries and their histologic analysis. Only the group treated with the essential oil of L. gracilis genotype 106 at the LC50 had no change compared with the control. The other groups showed the following changes in oocytes I to V: vacuolation, chorion deformation, disorganization of yolk granules, and irregularities at the cell periphery, causing incomplete process of vitellogenesis. Thus, the essential oils tested in this study may be potent products for the control of cattle ticks and thereby preventing further life cycles.

Assessment of different Lippia sidoides genotypes regarding their acaricidal activity against Rhipicephalus (Boophilus) microplus.

The aim of this study was to select different genotypes of Lippia sidoides with the highest activity against larvae and engorged females of the tick Rhipicephalus (Boophilus) microplus. The germplasms studied were LSID006, LSID102, LSID103 and LSID104. The LSID104 genotype, that presented carvacrol as a major constituent, was the germplasm with the worst larvicide effect (LC50 2.99 mg/mL). The LSID006 genotype was the least effective against engorged females (LC50 12.46 mg/mL), and it was chemically similar to the LSID102 genotype, which presented the highest acaricide activity (LC50 2.81 mg/mL). We conclude that chemical similarity of the germplasms was not correlated with acaricide activity against R. (B.) microplus. The essential oil of L. sidoides is a potent natural agent. However, the findings of this work provide a better understanding for product development based on this natural product, which must consider synergic effects or the action of minor compounds.

Assessment of different Lippia sidoides genotypes regarding their acaricidal activity against Rhipicephalus (Boophilus) microplus / Avaliação da atividade carrapaticida do óleo essencial de diferentes genótipos de Lippia sidoides sobre Rhipicephalus (Boophilus) microplus

Abstract The aim of this study was to select different genotypes of Lippia sidoides with the highest activity against larvae and engorged females of the tick Rhipicephalus (Boophilus) microplus. The germplasms studied were LSID006, LSID102, LSID103 and LSID104. The LSID104 genotype, that presented carvacrol as a major constituent, was the germplasm with the worst larvicide effect (LC50 2.99 mg/mL). The LSID006 genotype was the least effective against engorged females (LC50 12.46 mg/mL), and it was chemically similar to the LSID102 genotype, which presented the highest acaricide activity (LC50 2.81 mg/mL). We conclude that chemical similarity of the germplasms was not correlated with acaricide activity against R. (B.) microplus. The essential oil of L. sidoides is a potent natural agent. However, the findings of this work provide a better understanding for product development based on this natural product, which must consider synergic effects or the action of minor compounds.

Resumo O objetivo deste trabalho foi selecionar genótipos de Lippia sidoides que apresentem maiores atividades em larvas e fêmeas ingurgitadas do carrapato Rhipicephalus (Boophilus) microplus. Os genótipos estudados foram LSID006, LSID102, LSID103 e LSID104. O genótipo LSID104, o único a conter o monoterpeno carvacrol como um dos principais constituintes, foi o que apresentou o menor efeito larvicida (CL50 2,99 mg/mL). O genótipo LSID006 apresentou menor efeito sobre fêmeas ingurgitadas (CL50 12,46 mg/mL), entretanto foi quimicamente similar ao genótipo LSID102, que apresentou a maior atividade carrapaticida (CL50 2,81 mg/mL). Conclui-se que a semelhança química dos genótipos não se correlaciona com a atividade carrapaticida contra R. (B.) microplus. O óleo essencial de L. sidoides é um agente natural potente e os resultados deste trabalho proporcionam um melhor entendimento para o desenvolvimento de produtos com base neste produto natural, devendo ser considerado os efeitos sinérgicos ou a ação de compostos presentes em menores concentrações.

[Ectoparasites of small wild mammals from the adjacent areas of Itapecuru River and Environmental Preservation Area of Inhamum, state of Maranhão, Brazil]. / Ectoparasitos de pequenos mamíferos silvestres de áreas adjacentes ao Rio Itapecuru e Área de Preservação Ambiental do inhamum, estado do Maranhão, Brasil.

During fauna studies, thirty-six wild mammals were collected in adjacent areas of Itapecuru River and Environmental Preservation area of Inhamum, state of Maranhão, Brazil. They were sampled for ectoparasites. The following specimens of the order Rodentia and its respective ectoparasites were identified: Akodon sp. (Androlaelaps sp. and Laelaps sp.), Oecomys sp. (Androlaelaps sp. and Amblyomma cajennense), Oligoryzomys sp. (Androlaelaps sp. Laelaps sp. and Amblyomma sp.) e Oryzomys megacephalus (A. cajennense). In Calomys callosus no ectoparasite was found. It was observed infestation in the order Didelphimorphia as follows: Didelphis marsupialis (Androlaelaps sp., Laelaps sp. and larvae of Diptera Cyclorrhapha); Gracilinanus sp. (Laelaps sp. and larvae of Diptera Cyclorrhapha), Monodelphis domestica (Poplygenis (Polygenis)), Cummingsia sp., Amblyomma sp. and Androlaelaps sp.). Marmosa sp. e Thylamis sp. had no ectoparasites. From the captured hosts 56% were infested, 82% and 44% rodents and marsupials, respectively. Mites from the family Laelapidae presented the great diversity of hosts and genus.