Essential oils and isolated compounds for tick control: advances beyond the laboratory.

BACKGROUND: Tick control is a worldwide challenge due to its resistance to acaricides. Essential oils (EOs) and isolated compounds (EOCs) are potential alternatives for tick control technologies. METHODS: A review with EOs and EOCs, under field and semi-field conditions, was performed based on Scopus, Web of Science and PubMed databases. Thirty-one studies published between 1991 and 2022 were selected. The search was performed using the following keywords: "essential oil" combined with "tick," "Ixodes," "Argas," "Rhipicephalus," "Amblyomma," "Hyalomma," "Dermacentor," "Haemaphysalis" and "Ornithodoros." The words "essential oil" and "tick" were searched in the singular and plural. RESULTS: The number of studies increased over the years. Brazil stands out with the largest number (51.6%) of publications. The most studied tick species were Rhipicephalus microplus (48.4%), Ixodes scapularis (19.4%), Amblyomma americanum and R. sanguineus sensu lato (9.7% each). Cattle (70%) and dogs (13%) were the main target animal species. Regarding the application of EOs/EOCs formulations, 74% of the studies were conducted with topical application (spray, pour-on, foam, drop) and 26% with environmental treatment (spray). Efficacy results are difficult to evaluate because of the lack of information on the methodology and standardization. The nanotechnology and combination with synthetic acaricides were reported as an alternative to enhance the efficacy of EOs/EOCs. No adverse reactions were observed in 86.6% of the studies evaluating EOs/EOCs clinical safety. Studies regarding toxicity in non-target species and residues are scarce. CONCLUSIONS: This article provides a comprehensive review on the use of EOs and EOCs to reduce tick infestations, in both the hosts and the environment. As future directions, we recommend the chemical characterization of EOs, methodology standardization, combination of EOs/EOCs with potential synergists, nanotechnology for new formulations and safety studies for target and non-target organisms, also considering the environmental friendliness.

Thymol and eugenol against Rhipicephalus sanguineus sensu lato engorged females: Biological, histopathological and bioinformatic analysis.

The aim of this study was to evaluate the reproductive biology and histopathology of the ovaries of engorged females of Rhipicephalus sanguineus sensu lato exposed to combinations of thymol and eugenol, as well as to evaluate in silico the possible interactions of thymol and eugenol in tick cell membranes. To evaluate the tick reproductive biology, the adult immersion test (AIT) was performed, in which the engorged females were immersed in solutions of thymol and eugenol, combined or alone, at concentrations of 2.5 and 5.0 mg/mL. Two control groups (water and 3% DMSO) were also performed. The ticks were kept in a controlled chamber (B.O.D - 27 ± 1 °C and 80% ± 5% RH) to evaluate egg production and viability. To perform the ovaries histopathological evaluation, females were immersed in combination of thymol and eugenol (each at 2.5 and 5.0 mg/mL) and control (water and 3% DMSO) solutions. After immersion, the females were kept in B.O.D (27 ± 1 °C and RH of 80% ± 5%) for four days, they were dissected and the ovaries processed for histological analysis. In addition, an in silico analysis was performed using PASS online® software to predict probability activity (PA) of thymol and eugenol in cell membranes. The treatment with the combination of thymol and eugenol (each at 5.0 mg/mL) caused a reduction (p < 0.01) in oviposition, while the treatments with thymol (5.0 mg/mL) and combination of thymol and eugenol (5.0 mg/mL) reduced (p < 0.05) the egg viability. The treatment with combination of thymol and eugenol (5.0 mg/mL) resulted in a control percentage of 99.9%, while in the other treatments, control percentages below 56% were observed. Oocytes from the females exposed to the combinations of thymol and eugenol (each compound at 2.5 mg/mL) showed histopathological changes, except on oocyte V, while those treated with these compounds alone at 2.5 mg/mL, did not reveal any change. Changes in the shape of the oocyte, presence of vacuoles in the cytoplasm and germinal vesicle, reduction and fusion of yolk granules and rupture of some oocytes were observed. In silico analysis, showed that these compounds can act as membrane permeability inhibitors, membrane permeability agonists, membrane integrity antagonists and apoptosis agonists. We conclude that the combination of thymol and eugenol causes changes in the reproductive biology and morphophysiology of engorged females oocytes. The in silico analysis using thymol and eugenol revealed the possibility of disorganization in the cell membranes, a fact that may explain the histopathological alterations observed.

Comparison of the efficacy of different methods to apply acaricides for control of Rhipicephalus (Boophilus) microplus.

The present study compared the efficacy of different methods to apply an acaricide formulation to control Rhipicephalus (Boophilus) microplus. To compare the methods, an acaricide blend containing three active ingredients (a pyrethroid and two organophosphates) was used. In experiment 1 (farm 1: Goiânia, GO, Brazil), three methods were tested: a backpack sprayer (BS), power sprayer (PS) and spray race (SR). In experiment 2 (farm 2: São José do Rio Pardo, SP, Brazil), two methods were tested: BS and PS. In both experiments, 10 cattle with similar tick burdens were used. On day 0 in both experiments, the animals were treated with the acaricide. On day +1 (only in experiment 1), +3, +7, +14, +21, +28 and +35 (only in experiment 2), tick counts were performed to determine the control efficacy. The time application, pressure (KPa), volume applied (L) and ergonomic aspects of each spraying system were also evaluated. The adult immersion test (AIT) using three different acaricide blends (combinations of pyrethroid + organophosphate) was performed to compare the susceptibility of strains of each farm. In experiment 1, all treatments significantly reduced (p < 0.05) the number of ticks on the animals, and PS resulted in the greatest acaricide efficacy since day +1. In experiment 2, both treatments (PS and BS) reduced (p < 0.05) the tick burden, and as observed in experiment 1, PS resulted in the best reduction. The application times were 4.5, 150 and 330 s, while pressures were 306.8, 4,826.3 and 220.6 KPa for SR, PS and BS, respectively. In the AIT, the efficacy values were between 99.8 and 100% for the tick strain form farm 1 (Goiânia), while for tick strain from farm 2 (São José do Rio Pardo), the efficacy was between 67.2 and 80.9%. We conclude that the sprayer methods chosen influences the efficacy of the acaricide. All sprayer methods were efficient for acaricide application; the best efficacy was obtained using the PS, while the SR resulted in good efficacy and lower application time. The strain from farm 2 was less susceptible to all acaricides tested.

Combination of synthetic acaricides with (E)-cinnamaldehyde to control Rhipicephalus microplus.

This work had the objectives to (1) evaluate the susceptibility of various Rhipicephalus microplus populations to commercial acaricides, and (2) select commercial acaricides (50-80% effective) and evaluate the effects of binary combinations of the phenylpropanoid (E)-cinnamaldehyde with selected commercial acaricides to control R. microplus under laboratory and field conditions. Using adult immersion tests with 116 populations and 14 commercial acaricides, products showing 50-80% effectiveness (percent control) with the lowest number of active ingredients were selected. Acaricides containing amitraz or chlorfenvinphos were tested in combination with (E)-cinnamaldehyde on a field population (strain CM). We found that (E)-cinnamaldehyde enhanced the activity of both commercial acaricides against R. microplus larvae; however, the enhancement was more accentuated when using amitraz. Experiments combining (E)-cinnamaldehyde + amitraz on unfed larvae and engorged females from another population (strain Gyn) were performed, verifying (E)-cinnamaldehyde enhanced the activity of amitraz. In the field experiment, the application of (E)-cinnamaldehyde appeared toxic to the tick hosts (cattle). We concluded that (E)-cinnamaldehyde enhanced the activity of amitraz against unfed larvae and engorged females of R. microplus; however, in the field test this phenylpropanoid caused intoxication in the cattle. Studies searching for new combinations of compounds from essential oils with amitraz deserve attention, as well as studies to develop formulations using amitraz + (E)-cinnamaldehyde that will be efficient and will not have toxic effects in cattle.

Acaricidal activity of carvacrol and thymol on acaricide-resistant Rhipicephalus microplus (Acari: Ixodidae) populations and combination with cypermethrin: Is there cross-resistance and synergism?

This study evaluated the acaricidal activity of thymol and carvacrol on Rhipicephalus microplus populations with different resistance profiles and investigated the synergistic effect of combinations of these monoterpenes with cypermethrin. The adult immersion test (AIT) was used to characterize the susceptibility of tick populations (45 field populations) to synthetic acaricides: deltamethrin, amitraz and chlorfenvinphos. The larval packet test (LPT) was used to determine the LC50 values for thymol (25 tick populations) and carvacrol (20 tick populations). The susceptible strain Porto Alegre (POA) was used as a reference for calculating the resistance ratio (RR). Subsequently, larval immersion tests (LIT) were performed with combinations of cypermethrin with thymol or carvacrol to assess a synergistic effect. In the AIT, deltamethrin showed efficacy > 90% in one (2.2%) population tested (mean: 12.1 and 11.1 for populations 1-25 and 26-40, respectively), whereas amitraz and chlorfenvinphos showed efficacy > 90% for two (4.4%) populations (mean: 61.3 and 47.3 for populations 1-25 and 26-40, respectively) and eight (17.7%) populations (mean: 69.7 and 59.7 for populations 1-25 and 26-40, respectively). In the LPT, the LC50 values for thymol and carvacrol varied from 0.67 to 2.12 mg/mL and 0.55-3.21 mg/mL, with an average LC50 for populations of 1.49 and 1.75 mg/mL, respectively. For thymol, no resistance was observed in any of the populations, values of RR50 > 1.5. There was no correlation between the LC50 values for thymol and the efficacy of the chemical acaricides tested. Regarding carvacrol, for only one tick population had the value of RR50 > 1.5, indicating an incipient resistance. No correlation was observed between the LC50 values for carvacrol and the efficacy of tested acaricides. The combination of thymol and carvacrol with cypermethrin showed a synergistic effect in the resistant population (Jaguar - thymol 4.19 and carvacrol 3.67), and no synergistic interaction were showed in the susceptible population. Answering the questions we conclude that: 1 - The comparison between the LC50 values for thymol and carvacrol in field populations and the susceptible strain POA suggests the absence of cross-resistance (ticks and terpenes), and the differences between the LC50 values for thymol and carvacrol in the different R. microplus populations are inherent to the characteristics of each population tested; 2 - the combination of thymol or carvacrol with cypermethrin showed a synergistic effect with different activity according to the population of ticks.

Interleukin 17 A, hepatosplenic mansonic schistosomiasis and atherosclerosis / Interleucina 17 A, esquistossomose mansônica forma hepatoesplênica e aterosclerose

Objective: To evaluate serum concentrations of interleukin 17A (IL17A) in mansonic schistosomiasis patients, while the secondary objectives were to detect atherosclerotic disease, and to evaluate serum concentrations of interleukin 22 (IL22). Methods: This study included 30 patients with an established diagnosis of hepatosplenic mansonic schistosomiasis and 10 healthy volunteers. Comparative analyses of IL17A and IL22 concentrations were performed on the sera of patients and controls. Atherosclerosis was evaluated through carotid artery intima-media thickness measurement of the first 15 patients enrolled. Results: There were no differences in IL17 A concentrations (15.63±0.00pg/mL vs. 15.63±0.00pg/mL; p=1) and in IL22 concentrations (7.81±0.00pg/mL vs. 7.81±0.00pg/ mL, p=1) between patients and controls. The overall mean of intima-media thickness was 0.7±0.2mm. Conclusions: Serum concentrations of IL17A and IL22 were equal between patients and controls (undetectable or low concentrations). No patients had atheroma.

Objetivo: Avaliar as concentrações séricas de interleucina 17A (IL17A) em pacientes com esquistossomose mansônica, enquanto os objetivos secundários foram detectar a doença aterosclerótica e avaliar as concentrações séricas de interleucina 22 (IL22). Métodos: Este estudo incluiu 30 pacientes com diagnóstico estabelecido de esquistossomose mansônica em sua forma hepatoesplênica e 10 voluntários saudáveis. Análises comparativas de concentrações de IL17A e IL22 foram realizadas em soros de pacientes e controles. A aterosclerose foi avaliada pela medida do complexo íntima-média dos primeiros 15 pacientes recrutados. Resultados: Não houve diferença nas concentrações de IL17A (15,63±0,00pg/mL vs. 15,63±0,00pg/mL; p=1) e nas concentrações IL 2 (7,81±0,00pg/mL vs. 7,81±0,00pg/mL; p=1) entre os pacientes e controles. A média geral da espessura da camada média da íntima foi de 0,7±0,2mm. Conclusões: As concentrações séricas de IL17A e IL22 foram iguais entre pacientes e controles (concentrações indetectáveis ou baixa). Nenhum dos pacientes apresentou ateroma.

Portal Doppler ultrasound evaluation in myelitis by Schistosoma mansoni.

UNLABELLED: The mechanism for development of schistosomal myelitis has not yet been completely understood. Few publications have tried to establish a link between the general clinical presentation of the illness and its neurological manifestations. OBJECTIVE: To evaluated the portal blood flow in patients with schistosomal myelitis and controls. METHOD: Forty-three individuals were evaluated using portal Doppler ultrasound. Group I consisted of 13 patients with the spinal form of schistosomiasis. Group II included 10 patients with intestinal and hepatointestinal forms of schistosomiasis, but no neurological symptoms; while group III involved 20 healthy controls. RESULTS: Portal venous speed and portal venous flow were significantly elevated in group I (p<0.001) compared with the others. CONCLUSION: Doppler ultrasound demonstrated a situation of high flow within the portal venous system of patients with schistosomal myelitis.

Portal Doppler ultrasound evaluation in myelitis by Schistosoma mansoni / Avaliação pela ultrassonografia com Doppler portal na mielite pelo Schistosoma mansoni

The mechanism for development of schistosomal myelitis has not yet been completely understood. Few publications have tried to establish a link between the general clinical presentation of the illness and its neurological manifestations. Objective: To evaluated the portal blood flow in patients with schistosomal myelitis and controls. Method: Forty-three individuals were evaluated using portal Doppler ultrasound. Group I consisted of 13 patients with the spinal form of schistosomiasis. Group II included 10 patients with intestinal and hepatointestinal forms of schistosomiasis, but no neurological symptoms; while group III involved 20 healthy controls. Results: Portal venous speed and portal venous flow were significantly elevated in group I (p<0.001) compared with the others. Conclusion: Doppler ultrasound demonstrated a situation of high flow within the portal venous system of patients with schistosomal myelitis.

A fisiopatogênese da mielopatia esquistossomótica não é completamente entendida, sendo escassas as publicações que tentam inferir a relação entre a forma clínica da esquistossomose e suas manifestações neurológicas. Objetivo: Avaliar o fluxo sanguíneo do sistema porta em pacientes com mielite esquistossomótica, contribuindo no entendimento dos mecanismos que favorecem a chegada dos parasitas e/ou seus derivados ao sistema nervoso. Método: Foram avaliados 43 indivíduos pela Dopplerfluxometria portal. O grupo I constou de 13 pacientes com esquistossomose medular, sendo o grupo II composto por 10 portadores de formas intestinal e hepatointestinal (sem doença neurológica), e o grupo III, por 20 controles sadios. Resultados: A velocidade venosa portal e o fluxo venoso portal foram significativamente elevados (p-valor<0,001) no grupo I. Conclusão: A Dopplerfluxometria demonstrou a presença de estados hiperdinâmicos do leito vascular porta em pacientes com mielite pelo Schistosoma mansoni.

Índice de resitência arterial ovariano em pacientes com esquistossomose mansônica hepatoesplênica / Ovarian aterial resistance index in hepatosplenic mansoni schistosomiasis patients

A fim de avaliar a repercussão da hipertensão porta no índice de resistência (IR) arterial ovariano, vinte e duas mulheres portadoras de esquistossomose mansônica na forma hepatoesplênica com idades variando de 18 a 46 anos (média de idade 32,4±7,64) foram estudadas. Foram realizados exames com Doppler colorido transvaginal pelo mesmo observador, usando o equipamento Veluson 730 (GE), equipado com transdutor volumétrico multifrequencial de 6-9 MHz. Todas as pacientes foram examinadas no 22º dia do ciclo (fase luteal média) e o índice de resistência de Pourcelot foi usado como referencia (RI=S-D/S). O ciclo menstrual foi ovulatório em 17 (77) das mulheres. Foi observada diminuição significante na média das medidas do IR no ovário onde o corpo lúteo estava presente (0,430±0,026 versus 0,559±0,059) no ovário direito (p<0.00010), e (0,470±0,059 versus 0,561±0,075) no ovário esquerdo (p=0.0037). Os dados indicam que a hipertensão porta em portadoras de esquistossomose mansônica na forma hepatoesplênica não interfere no fenômeno natural de aumento de irrigação do ovário quando da ovulação.