Protective action of Tagetes minuta (Asteraceae) essential oil in the control of Rhipicephalus microplus (Canestrini, 1887) (Acari: Ixodidae) in a cattle pen trial

Antibacterial activity of plant extracts against Streptococcus equi subsp. zooepidemicus isolates from guinea pigs with lymphadenitis in Ecuador

Lymphadenitis is a commonly occurring and contagious disease in guinea pigs caused by different pathogens, including Streptococcus sp., Staphylococcus sp., and Corynebacterium sp. This study aimed to characterize the bacteria isolated from pus extracted from abscessed mandibular lymph nodes of diseased guinea pigs in Ecuador in 2019 and evaluate the in vitro antibacterial activity of the total extracts of three plant species. Isolates were recovered from three diseased guinea pigs with Lymphadenitis on a farm in Imbabura, Ecuador province. The bacteria were characterized through microbiological, biochemical, and molecular tests as Streptococcus equi subsp. zooepidemicus. Furthermore, the susceptibility of S. equi subsp. zooepidemicus to three plant extracts belonging to the Asteraceae family, Acmella ciliata, Bidens andicola, and Gazania splendens collected in Ecuador, were assessed in vitro by the microdilution method. Our data indicate that all the evaluated extracts showed activity, with a Minimum Inhibitory Concentration (MIC) of 22.50 mg/mL for Acmella ciliata, 11.25 mg/mL for Bidens andicola, and 5.60 mg/mL for Gazania splendens. Bidens andicola extract showed the highest efficacy with a % inhibition of 63.90 at the highest tested concentration (45 mg/mL). This is the first report on the bioactivity of these plant species against S. equi subsp. zooepidemicus.

Effect of Tagetes minuta essential oil on the central nervous system of unfed Rhipicephalus sanguineus sensu lato 'tropical lineage' ticks

Rhipicephalus sanguineus sensu lato 'tropical lineage' (Acari: Ixodidae) is considered a sanitary concern due to its role as a disease vector. Tick strains resistant to synthetic acaricides have caused difficulties in their control, besides synthetic acaricides are harmful to the environment and to the health of non-target animals. The research of plants with acaricidal and repellent properties has proved to be an efficient alternative in tick control. The genus Tagetes spp. excels for its use as traditional pest control in households and plantations and also for its potential as an acaricide against R. sanguineus under laboratory conditions. The first aim of the present study was to evaluate the effect of different doses of Tagetes minuta essential oil (TMEO) on the central nervous system (synganglion) in unfed R. sanguineus adults. The histological analysis of synganglion exposed to the different concentrations of TMEO and amitraz 12.5% (50% of the recommended dose in the package insert) showed a significant effect with signs of cell damage including volume increase, loss of shape, and vacuolization, in addition to chromatin alterations such as condensation, margination, and fragmentation. TMEO were analyzed by gas chromatography coupled with mass spectrometry showing the presence of 21 compounds that according to their chemical structure are classified as terpenoids. Among them (Z)-β-ocimene, ocimene, (Z)-tagetone, and verbenone were found in major quantities.

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.

Acaricidal assessment of the fungal extract of Pleurotus ostreatus against Rhipicephalus microplus: Role of in vitro and in silico analysis

The Pleurotus ostreatus mushroom, commonly referred to as the oyster mushroom, is a widely consumed edible mushroom that grows in clusters on dead or dying trees. In addition to its culinary uses, research has found that the mushroom may also have potential medicinal properties. The current study investigated the potential use of a fungal extract from P. ostreatus as a natural acaricide against Rhipicephalus microplus, a major vector of economically significant infections and one of the most significant bovine ectoparasites. The study used the adult immersion test (AIT) and the larvae packet test (LPT) to evaluate the effectiveness of the extract against ticks. To evaluate the reproductive effect of the fungal extract on the reproduction of R. microplus engorged females, the eggs were tested for weight and egg-laying index. The results of the study showed that P. ostreatus extract had a significant acaricidal effect, with a 40 mg/mL concentration causing 89 ± 2.64% mortality in R. microplus larvae compared to the 91.00 ± 3.60% mortality by the positive control at 48 h interval. Whereas in the AIT, the extract inhibited 39.86 ± 4.13% of oviposition. The study also used in silico approach to further examine the binding mechanisms of the compounds in the fungal extract to the target protein R. microplus Triosephosphate isomerase RmTIM, using molecular docking in AutoDock Vina software. Docking scores of -8.3, -7.7 and -6.9 kcal/mol, respectively, showed that rutin, naringin and myricitin had significant interactions with the active site residues of the target protein. Our results suggest that P. ostreatus extract may be a potential alternative to traditional acaricides for controlling R. microplus in livestock.

Acaricidal Efficacy of Plants from Ecuador, Ambrosia peruviana (Asteraceae) and Lepechinia mutica (Lamiaceae) against Larvae and Engorged Adult Females of the Common Cattle Tick, Rhipicephalus microplus

Control measures against common cattle tick Rhipicephalus microplus are of the upmost importance because of considerable, deleterious impact on a farm’s economy. Due to resistance phenomena to synthetic acaricides being a constraint in affected farms, the search for plant derivatives as acaricides has increased dramatically in recent years. In this work, essential oils obtained from two Ecuadorian plants, Ambrosia peruviana and Lepechinia mutica (EO_Ap, EO_Lm), traditionally used as insecticides in indigenous communities, were studied on larvae and engorged females at the parasitic stages of R. microplus. Larvae and females were treated with five (0.0625, 0.125, 0.25, 0.50 and 1%) and six concentrations (0.125, 0.25, 0.50, 1, 2 and 4%), respectively, of each EOs_Ap/Lm. A 98–99% larval mortality was achieved with 0.5% of both EOs_Ap/Lm. EO_Ap inhibited oviposition and egg hatching up to 82% and 80%, respectively, and had an overall efficacy of 93.12%. Efficacy of EO_Lm was 72.84%, due to the low influence of EO_Lm on reproductive parameters. By steam distillation and GC-MS analysis, γ-Curcumene was identified as the main constituent (52.02%) in the EO_Ap and Shyobunol (10.80%) in EO_Lm. The results suggest that major components of both essential oils should be further studied as promissory acaricides against R. microplus.

Acaricidal and Repellent Effects of Essential Oils against Ticks: A Review

Tick control is a priority in order to prevent the transmission of vector-borne diseases. Industrial chemical acaricides and repellents have been the most efficient tools against hard ticks for a long time. However, the appearance of resistances has meant the declining effectiveness of the chemicals available on the market. The trend today is to develop alternative control methods using natural products to replace nonefficient pesticides and to preserve the efficient ones, hoping to delay resistance development. Traditional in vitro evaluation of acaricidal activity or resistance to synthetic pesticides have been reviewed and they mainly focus on just one species, the one host tick (Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)). Recent reports have called for the standardization of natural product components, extraction techniques, and experimental design to fully discover their acaricidal potential. This study reviews the main variables used in the bibliography about the efficiency of natural products against ticks, and it proposes a unification of variables relating to ticks, practical development of bioassays, and estimation of ixodicidal activity.

Antineoplastic potential and chemical evaluation of essential oils from leaves and flowers of Tagetes ostenii Hicken

Breast and cervical cancer represent a major problem of women's global public health. Here, we investigated the chemical composition of essential oils from leaves and flowers of T. ostenii and the antineoplastic potential in a cervical cancer and breast cancer cell line, SiHa and MCF-7; and non-tumoral cells, HaCat. The chemical analysis revealed a predominance of oxygenated monoterpenes in both essential oils. The IC50 after 24 h of treatment was 72 ng/mL for EO 1 and 83 ng/mL for EO 2 in SiHa cells. For MCF-7 the IC50 was 174.3 ng/mL for EO 1. For HaCat cells it was 54.45 ng/mL for EO 1 and 20.83 ng/mL for EO 2. A synergistic effect with both essential oils and cisplatin was also verified. SiHa cells had their wound healing capacity reduced after 48 h of treatment with EO 2 and both essential oils were able to significantly inhibit the adhesion process and clonogenic ability after 24 h of treatment. Our results suggest a long-lasting inhibitory activity in SiHa cells because of the low recovery capacity of cells after treatment withdrawal. Flow cytometer with annexin V/propidium iodide demonstrated a majority cell death through late apoptosis after 24, 48 and 72 hours of treatment.

Repellent and acaricidal activity of essential oils and their components against Rhipicephalus ticks in cattle

Ticks, particularly the Rhipicephalus which are the most prevalent and invasive affect 80 % of the cattle population worldwide. Through transmission of pathogens, tick worry and physical damage to the hides, ticks cause economic loss of billions of dollars each year with 1 billion US dollars loss per annum reported only in Latin-America. These losses can be minimized only by successful management of Rhipicephalus ticks. Various strategies like chemical control, vaccination and biological control are aimed at control of Rhipicephalus ticks. There are some serious limitations associated with them like tick resistance, drug toxicity, antigenic variations etc. In contrast to these issues related with chemical tick control, the botanicals particularly the essential oils obtained from aromatic plants of medicinal importance are eco-friendly and non-toxic to most host. In recent years, essential oils-based control of cattle ticks has gained considerable attraction of scientists all over the world as depicted from this review. A comprehensive effort has been made to critically analyze the role of essential oils in controlling Rhipicephalus ticks with particular emphasis on the mode of action of bioactive compounds both as repellents and acaricides. Furthermore, we have pointed out the most important challenges which need to be addressed for development and commercialization of an essential oil based anti-tick product.

Insecticidal activity of marigold Tagetes patula plants and foliar extracts against the hemipteran pests, Lygus hesperus and Bemisia tabaci

The western tarnished plant bug, Lygus hesperus Knight (Hemiptera: Miridae) and the whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) are key hemipteran pests of numerous crop plants throughout the western United States and Mexico. Management in the U.S. currently relies on only a few insecticides and is threatened by the evolution of resistance. New chemistries or alternative management strategies are needed to reduce selection pressure on current insecticides and enhance control. Here, we investigated the bio-insecticidal toxicity of the French marigold, Tagetes patula Linnaeus (Asterales: Asteraceae), against both L. hesperus and B. tabaci. Assays indicated significantly reduced survival of both pest species on T. patula plants, and in diet incorporation assays containing aqueous and methanolic marigold foliar extracts. Mortality was concentration-dependent, indicating the presence of one or more extractable toxicants. These data suggest that T. patula plants have insecticidal constituents that might be identified and developed as novel alternatives to conventional chemical treatments.

Acaricidal effect of Schinus molle (Anacardiaceae) essential oil on unengorged larvae and engorged adult females of Rhipicephalus sanguineus (Acari: Ixodidae)

The current concern about resistance to acaricides and the impact of toxic waste on the environment has led to the search of vegetal alternatives in the control of the brown tick of the dog Rhipicephalus sanguineus. Schinus molle L. (Anacardiaceae) derivatives have been associated with insecticidal, antimicrobial and antiprotozoal activities and essential oil showed to be lethal to R. microplus larvae. This study aimed at evaluating the acaricidal effect of essential oil of S. molle (EO_Sm) on engorged adult females and larval stages of R. sanguineus. One-hundred engorged females were obtained from the ears, interdigital spaces, neck, groin and base of the tail of two cross-bred dogs. The larvae package test was accomplished with 21-day-old larvae and five concentrations (v/v) of EO_Sm (0.125, 0.25, 0.50, 1 and 2%) in an anionic detergent, a synthetic acaricide (cypermethrin) and detergent and deionized water as controls. The immersion adult test was carried out with nine concentrations (0.125, 0.25, 0.50, 1, 2, 4, 8, 16, 20%) of the EO_Sm. At the concentration of 2%, EO_Sm caused 99.3% of larval mortality. In adults, inhibition of oviposition, egg hatching (EH) and reproductive efficiency (RE) values were dose-dependent from 4 to 20% EO_Sm; the lowest values of EH (29.62) and RE (22.61) were achieved with 20% EO_Sm. Strong and negative correlations were found between concentration of EO_Sm and EH (r = - 0.948) and between concentration of EO_Sm and RE (r = - 0.985). This study demonstrated for the first time the acaricidal effect of EO_Sm on larvae and reproductive parameters of engorged adult females of R. sanguineus.

Tagetones A and B, new cytotoxic monocyclic diterpenoids from flowers of Tagetes minuta

Tagetones A (1) and B (2), two new monocyclic diterpenoids were isolated from the n-hexane fraction of fresh flowers of Tagetes minuta L. (Asteraceae). Their structures were established by multiple spectroscopic methods (IR, HR-ESI-MS, and 1D-, and 2D-NMR), in addition to comparison with literature data. Compound 1 showed cytotoxic activity towards MCF7 and A549 cancer cells with IC₅₀ values being 4.68 and 4.24 µmol·L^-1, respectively, compared to doxorubicin (IC₅₀ 0.13 and 1.12 µmol·L^-1, respectively). Compound 2 also exhibited significant activity against HCT116 cancer cells (IC₅₀, 6.30 µmol·L^-1).

Plant products and secondary metabolites with acaricide activity against ticks

The present review documents the results of studies evaluating the acaricidal activity of different plant products and secondary metabolites against ticks that are resistant and susceptible to conventional acaricides. Studies published from 1998 to 2016 were included. The acaricidal activity of plant extracts, essential oils and secondary compounds from plants have been evaluated using bioassays with ticks in the larval and adult stages. There is variable effectiveness according to the species of plant and the concentrations used, with observed mortalities ranging from 5 to 100% against the Rhipicephalus (Boophilus), Amblyomma, Dermacentor, Hyalomma, and Argas genera. A number of plants have been reported to cause high mortalities and/or affect the reproductive capacity of ticks in the adult phase. In the majority of these trials, the main species of plants evaluated correspond to the families Lamiaceae, Fabaceae, Asteraceae, Piperaceae, Verbenaceae, and Poaceae. Different secondary metabolites such as thymol, carvacrol, 1,8-cineol and n-hexanal, have been found to be primarily responsible for the acaricidal activity of different essential oils against different species of ticks, while nicotine, dibenzyldisulfide and dibenzyltrisulfide have been evaluated for plant extracts. Only thymol, carvacrol and 1,8-cineol have been evaluated for acaricidal activity under in vivo conditions. The information in the present review allows the conclusion that the secondary metabolites contained in plant products could be used as an alternative for the control of ticks that are susceptible or resistant to commercial acaricides.

Efficacy of Tagetes minuta (Asteraceae) essential oil against Rhipicephalus sanguineus (Acari: Ixodidae) on infested dogs and in vitro

Ticks from Rhipicephalus sanguineus complex are widely distributed in the world and one species from this complex is the most common tick on dogs in Brazil, notably in urban areas. This tick is a vector of several diseases. Among others it transmits the agent of canine Ehrlichiosis, a major dog infectious disease and the agent of Rocky Mountain spotted fever. This tick can spread rapidly and develop intolerable infestations within no time. Currently tick control is done with acaricides and demand for such drugs has grown fast. However, R. sanguineus has already developed resistance to the main active compounds and the development of new acaricides is necessary. Many essential oils of plants have acaricidal effect and may be an important source of molecules for the synthesis of new acaricide products. In this study, we evaluated the effectiveness of a new herbal phytotherapic, consisting of the essential oil of Tagetes minuta L., against R. sanguineus in vitro and on dogs undergoing experimental infestations. The product displayed 100% efficacy against larvae, nymphs and adults of the tick on all tested conditions.