Influence of essential oil fractionation by vacuum distillation on acaricidal activity against the cattle tick

The aim of this work was to study the influence of essential oil fractionation on acaricidal activity against the cattle tick Rhipicephalus (Boophilus) microplus. The citronella (Cymbopogon winterianus J.) and pepper tree (Schinus molle L.) essential oils were fractionated by vacuum distillation yielding fractions that were analyzed by the GC/MS. Laboratory tests were carried out to determine the effect of the total essential oil and fractions on larvae of the cattle tick R. (B.) microplus. The fractions 04 and 05 of the C. winterianus essential oil were the most active showing LC50 values of 1.20 and 1.34 μL/mL, respectively. The LC50 of the total oil was 3.30 μL/mL while the effect of the fractions 01, 02 and 03 was less pronounced, with LC50 values of 4.37, 4.24 and 3.49 μL/mL, respectively. The fraction 03 of the S. molle essential oil was the most active showing LC50 value of 8.80 μL/mL while the fractions 01 and 02 did not show toxic effects on the larvae.

Effect of Calea serrata Less. n-hexane extract on acetylcholinesterase of larvae ticks and brain Wistar rats.

Acetylcholinesterase (AChE), an enzyme that hydrolyses acetylcholine (ACh) at cholinergic synapses, is a target for pesticides and its inhibition by organophosphates leads to paralysis and death of arthropods. It has been demonstrated that the n-hexane extract of Calea serrata had acaricidal activity against larvae of Rhipicephalus (Boophilus) microplus and Rhipicephalus sanguineus. The aim of the present study was to understand the mechanism of the acaricidal action of C. serrata n-hexane extract are specifically to investigate the in vitro anticholinesterase activity on larvae of R. microplus and in brain structures of male Wistar rats. The n-hexane extract significantly inhibited in vitro acetylcholinesterase activity in R. microplus larvae and rat brain structures. The results confirm that inhibition of acetylcholinesterase is a possible mechanism of action of hexane extract at C. serrata.

Acaricidal properties of the essential oil and precocene II obtained from Calea serrata (Asteraceae) on the cattle tick Rhipicephalus (Boophilus) microplus (Acari: Ixodidae).

Calea serrata Less. (Asteraceae), an endemic species of south Brazil known as "quebra-tudo", is used in Afro-Brazilian religious rituals and in folk medicine for treating liver disorders. Phytochemical studies of the n-hexane extract of this plant demonstrated the presence of precocene II, a benzopyran derivative known for its insecticidal activity. The aim of this work was to isolate this benzopyran and determine the chemical composition of the essential oil of C. serrata and further to evaluate the acaricidal activity of the essential oil and precocene II against the larvae of Rhipicephalus (Boophilus) microplus. The LC(99.9) and LC(50) values obtained with the oil, which presents precocene II and sesquiterpenes, were 3.94 µL/mL and 0.28 µL/mL, respectively. For precocene II this values were 4.25mg/mL and 1.78 mg/mL, respectively. The results indicate a synergistic interaction between the components of the oil and precocene II.

Acaricidal properties of the essential oil from Hesperozygis ringens (Lamiaceae) on the cattle tick Riphicephalus (Boophilus) microplus.

Hesperozygis ringens (Benth.) Epling (Lamiaceae) is a strongly aromatic plant employed popularly for its antiparasitic properties. The leaves afforded 4% of essential oil constituted mainly by pulegone (86%). Laboratory tests were carried out to determine the toxicity of the essential oil species on engorged females and larvae of the cattle tick Riphicephalus (Boophilus) microplus using the adult immersion test (AIT) and the larval immersion test (LIT). It was observed that the essential oil at the concentration of 50 microL/mL and 25 microL/mL inhibited the egg laying significatively in relation to the controls and the eggs from these treated females were affected by the oil; the hatching was inhibited in 95% and 30%, respectively. In the LIT it was verified that the LC(99.9), LC(50) and LC(1) was 0.541 microL/mL, 0.260 microL/mL and 0.015 microL/mL, respectively. Pulegone, isolated from the oil, showed similar effect on the females and on the larvae, indicating that it is responsible for the oil activity.

Chemical composition and toxicity of the essential oils from Cunila species (Lamiaceae) on the cattle tick Rhipicephalus (Boophilus) microplus.

The essential oils obtained from the aerial parts of five species of Cunila (Lamiaceae) native to Southern Brazil were analyzed by GC and GC/MS. The oil of Cunila angustifolia was characterized by sabinene; Cunila incana is rich in alpha-pinene and beta-pinene, Cunila spicata and Cunila microcephala presented menthofuran as the main component, and in the essential oil of Cunila incisa, the major component was 1,8-cineole. Laboratory tests were carried out to determine the effect of the essential oils of the above cited plants on larvae of the cattle tick Riphicephalus (Boophilus) microplus. C. angustifolia, C. incana, and C. spicata were the most active samples killing almost the totality of the larvae. C. incisa and C. microcephala showed low acaricidal effect.

Acaricidal activity of limonene, limonene oxide and beta-amino alcohol derivatives on Rhipicephalus (Boophilus) microplus.

Limonene, limonene oxide and eight beta-amino alcohol derivatives obtained by synthesis were investigated for the effect on egg hatchability and mortality rates of newly hatched larvae of the cattle tick Rhipicephalus (Boophilus) microplus. At the doses between 10 microg/ml and 2.5 microg/ml all the compounds were highly lethal to the larvae and some of them showed activity at lower concentrations. The effect on the eggs hatchability was observed in all the treatments.

Acaricidal activity of the hyacinthacine analogues derived from pyrrolizidine alkaloids on Rhipicephalus (Boophilus) microplus.

This study reports the effect of six hyacinthacine analogues derived from pyrrolizidine alkaloids on egg hatchability and mortality rates of newly hatched larvae of the cattle tick Rhipicephalus (Boophilus) microplus. All the compounds were toxic to the larvae of the ticks and inhibited the eggs hatchability in the higher concentration tested (5 microg/ml). Even in the lowest concentration (0.625 microg/ml), some effect in the eggs hatchability was observed.

Acaricidal activity of Calea serrata (Asteraceae) on Boophilus microplus and Rhipicephalus sanguineus.

Calea serrata (Asteraceae) is an endemic Southern Brazilian plant species used for religious and medicinal purposes. Previous study revealed the presence of chromenes, a class of natural compounds that possess insecticidal properties. This study reports the effect of the hexane extract from the aerial parts of this plant on egg hatchability, egg production and mortality rates of newly hatched larvae of the cattle tick Boophilus microplus. Larvae of Rhipicephalus sanguineus, the brown dog tick, received the same treatment. The extract was toxic to the eggs of B. microplus and to the larvae of both B. microplus and R. sanguineus.

Chemical composition and larvicidal properties of the essential oils from Drimys brasiliensis Miers (Winteraceae) on the cattle tick Rhipicephalus (Boophilus) microplus and the brown dog tick Rhipicephalus sanguineus.

The essential oil obtained from leaves and stem barks of the Southern Brazilian native Drimys brasiliensis Miers, a tree with medicinal properties, was analyzed by gas chromatography (GC) and GC/mass spectrometry (MS). The oil was characterized by sesquiterpenoids (66%), cyclocolorenone being the most abundant (30.4%), followed by bicyclogermacrene (11.8%) and alpha-gurjunene (6.0%). Laboratory tests were carried out to determine the toxicity of the essential oil on larvae of the cattle tick Rhipicephalus (Boophilus) microplus and the brown dog tick Rhipicephalus sanguineus by the larval immersion test. It was observed that the oil was lethal, killing 100% of the larvae of both ticks at the doses of 25, 12.5, and 6.25 microl/ml. The lowest dose tested, 3.125 microl/ml, was also toxic, killing 95-98% of the larvae.

Acaricidal properties of extracts from the aerial parts of Hypericum polyanthemum on the cattle tick Boophilus microplus.

Laboratory tests were carried out on larvae and adults of the cattle tick Boophilus microplus to determine the toxicity of n-hexane and crude methanolic extracts of Hypericum polyanthemum (Guttiferae) using the larval immersion test (LIT) and adult immersion test (AIT). In the AIT, the effectiveness of treatment against engorged females was assessed by measuring egg production: the n-hexane extract was found to have a small effect on the egg laying at the highest concentration (19.2% of egg-laying inhibition) whilst the crude methanolic extract did not affect the egg production. For the LIT the n-hexane extracts were highly toxic to the larvae at all the concentrations (100% of mortality). The crude methanolic extract was also toxic to the larvae at higher concentrations killing 100, 96.7, 84.7 and 52.7% at the concentrations of 50, 25, 12.5, and 6.25 mg/ml, respectively, 48 h after the immersion of the acarus.

Effects of solvents and surfactant agents on the female and larvae of cattle tick Boophilus microplus.

Many natural compounds have low water solubility and need to be dissolved in organic solvents, or surfactant agents must be used before addition into experimental systems. Therefore, it is necessary to determine their toxicity. Experiments were performed aiming to select solvents to be used in the bioassays, searching new acaricide agents from plants. Laboratory tests were carried out on larvae and adults of the cattle tick Boophilus microplus to determine the sensibility of B. microplus female and larvae to different solvents (acetone, methanol, ethanol and 1% dimethyl sulfoxide) and surfactant agents (1% Tween 80 and 5% Triton X-100) using the larval immersion test (LIT) and adult immersion test (AIT). In the AIT, the effect of the treatments on engorged females was assessed by measuring egg production and hatching rate. Acetone was toxic to the adults promoting mortality of 100%. Methanol and ethanol caused 45.3 and 14.2% of mortality, respectively. The other tested substances were not toxic to the engorged females of B. microplus. In the LIT, it was observed that the larvae were more resistant; after 48 h, about 100% of the larvae were alive in all the treatments except with acetone that caused a mortality of 10%.

Espécies e prevalência das infestações por carrapatos em cães de rua da cidade de Porto Alegre, RS, Brasil / Species and prevalence of ticks infestations on stray dogs in Porto Alegre city, RS, Brazil

O objetivo deste trabalho foi identificar as espécies de carrapatos que parasitam os cães da área urbana de Porto Alegre e conhecer suas prevalências nesta população. Para isso, foram examinados 450 cães de rua de Porto Alegre, colhidos os carrapatos nos animais infestados e estes identificados ao estereomicroscópio por espécie e por estágio. Dentre os animais examinados, 52,44 por cento albergavam carrapatos e destes, 93,22 por cento estavam parasitados por Rhipicephalus sanguineus, 2,97 por cento por Amblyomma aureolatum e 3,81 por cento pelas duas espécies simultaneamente. Do total de carrapatos colhidos, a espécie mais abundante nos animais foi R. sanguineus representando 99,43 por cento desse total; foram encontrados ínstares de todos os estágios parasitários de R. sanguineus e só do estágio adulto de A.aureolatum.

The purpose of this study was to identify and to know the prevalence of ticks recovered from dogs of urban area of Porto Alegre, RS. Four hundred and fifty stray dogs were examined and the ticks found were identified according to the species and parasitic stage. A percentage of 52.44 percent of those dogs were infested with ticks, among these, 93.22 percent were parasitized by Rhipicephalus sanguineus, 2.97 percent by Amblyomma aureolatum and 3.81 percent by both species. R. sanguineus was the more prevalent species among infested animals representing 99.43 percent of the total number of ticks sampled. All parasitic stages of R. sanguineus were present on the stray dogs but only the adult stage of A. aureolatum was found.