ABSTRACT
The cattle tick, Rhipicephalus microplus (Canestrini, 1888) (Ixodida: Ixodidae), is the most important ectoparasite in cattle-breeding areas and is responsible for severe economic losses. Synthetic acaricides have been used to control this parasite. However, the need for safer products has stimulated the search for new acaricides, such as those to be obtained from medicinal plants. The essential oil of Syzygium aromaticum (clove) has many biological properties and shows great potential for use in veterinary applications. In the context of the need for new agents, this study investigated the in vitro properties of the hydrolate, essential oil and the main constituent of S. aromaticum, eugenol, in formulated and free applications against larvae and females of R. microplus. Eugenol and the essential oil caused 100% mortality in larvae at starting applications of 2.5 mg/mL and 5.0 mg/mL, respectively. The hydrolate showed no activity. Both eugenol and essential oil had good efficacy in adult immersion tests at 50 mg/mL and achieved 100% efficacy at a concentration of 100 mg/mL. The results of these tests reaffirm the important potential of clove essential oil and eugenol.
Subject(s)
Acaricides , Clove Oil , Eugenol , Rhipicephalus , Syzygium/chemistry , Tick Control , Animals , Female , Larva/growth & development , Rhipicephalus/growth & developmentABSTRACT
The effects of combinations of the monoterpenes thymol and carvacrol and the phenylpropanoid eugenol in larvae of Rhipicephalus microplus (Canestrini, 1888) (Acari: Ixodidae) and Rhipicephalus sanguineus sensu lato (s.l.) (Acari: Ixodidae) were assessed by the larval packet test. The CompuSyn program was used to make qualitative assessments of the effects (synergistic, additive and antagonistic) of the associations. The effects of all combinations tested against R. microplus larvae were synergistic, with combination indices (CIs) <0.70. When tested against R. sanguineus, eight of the mixtures showed a synergistic effect (CI < 0.70); only the carvacrol + thymol mixture at LC50 presented a moderate synergistic effect, with CIs between 0.70-0.90. This study is the first to determine the effects of the interactions of these substances in the control of these two tick species. The combinations of carvacrol + thymol, carvacrol + eugenol and thymol + eugenol have synergistic effects in R. microplus and R. sanguineus s.l. larvae.
Subject(s)
Acaricides , Eugenol , Monoterpenes , Rhipicephalus , Thymol , Animals , Cymenes , Drug Synergism , Larva/growth & development , Rhipicephalus/growth & development , Rhipicephalus sanguineus/growth & developmentABSTRACT
This work evaluated the in vitro effects of Steinernema glaseri on the biology of engorged Amblyomma cajennense nymphs. The ticks were exposed to infective juveniles (IJs) of S. glaseri at different concentrations. Each treatment was composed by 10 experimental units (EU = repetitions) in Petri dishes maintained at 27 ± 1º C and relative humidity (RH) > 80 ± 10% for 72 hours. Then the nymphs were transferred to Petri dishes free of nematodes for observation of the following parameters: pre-ecdysis period (PEP), ecdysis period (EP), molting period (MP), ecdysis percentage (%Ec) and mortality percentage (%Mt). The groups treated with 5,000 and 10,000 IJs/EU showed significant alterations in the PEP when compared to the control, while for the EP only the treatment with 10,000 IJs/EU produced any significant changes compared to the control. The MP did not differ significantly from the control in any of the treated groups. For the %Ec only the group treated with 10,000 IJs/EU differed significantly from the control. The greatest efficiency was obtained at the concentration of 10,000 IJs/EU, in which the mortality percentage was 13%. This demonstrates that the nematode utilized was not able to cause high mortality in engorged A. cajennense nymphs and agrees with other reports indicating that immature ticks are not highly susceptible to entomopathogenic nematodes.
Esse trabalho avaliou os efeitos in vitro de Steinernema glaseri sobre a biologia de ninfas ingurgitadas de Amblyomma cajennense. Os carrapatos foram expostos a juvenis infectantes (JI) de S. glaseri sob diferentes concentrações. Cada tratamento foi composto de 10 unidades experimentais (EU = repetições) em placas de Petri mantidas sob 27 ± 1º C e UR > 80 ± 10% por 72 horas. Em seguida, as ninfas foram transferidas para placas de Petri isentas de nematoides para observação dos seguintes parâmetros: período de pré-ecdise (PPE), período de ecdise (PE), período de muda (PM), porcentagem de ecdise (%Ec) e porcentagem de mortalidade (%Mt). Os grupos tratados com 5.000 e 10.000 JI/UE mostraram alterações significativas no PPE quando comparados com o controle, enquanto para o PE somente o tratamento com 10.000 JI/UE produziu mudanças significativas quando comparado com o controle. Não houve diferença significativa do PM em relação ao grupo controle em nenhum dos tratamentos e, para a %Ec, somente o grupo tratado com 10.000 JI/UE diferiu significativamente do controle. A maior eficiência foi obtida com a concentração de 10.000 JI/EU na qual a mortalidade foi de 13%. Isso demonstra que o nematoide utilizado não foi capaz de causar alta mortalidade em ninfas ingurgitadas de A. cajennese e concorda com outros relatos indicando que carrapatos imaturos não são altamente susceptíveis a nematoides entomopatogênicos.
