Repellent activity of essential oils to the Lone Star tick, Amblyomma americanum.

BACKGROUND: The Lone Star tick, Amblyomma americanum is important to human health because of a variety of pathogenic organisms transmitted to humans during feeding events, which underscores the need to identify novel approaches to prevent tick bites. Thus, the goal of this study was to test natural and synthetic molecules for repellent activity against ticks in spatial, contact and human fingertip bioassays. METHODS: The efficacy of essential oils and naturally derived compounds as repellents to Am. americanum nymphs was compared in three different bioassays: contact, spatial and fingertip repellent bioassays. RESULTS: Concentration response curves after contact exposure to 1R-trans-chrysanthemic acid (TCA) indicated a 5.6 µg/cm2 concentration required to repel 50% of ticks (RC50), which was five- and sevenfold more active than DEET and nootkatone, respectively. For contact repellency, the rank order of repellency at 50 µg/cm2 for natural oils was clove > geranium > oregano > cedarwood > thyme > amyris > patchouli > citronella > juniper berry > peppermint > cassia. For spatial bioassays, TCA was approximately twofold more active than DEET and nootkatone at 50 µg/cm2 but was not significantly different at 10 µg/cm2. In spatial assays, thyme and cassia were the most active compounds tested with 100% and 80% ticks repelled within 15 min of exposure respectively and was approximately twofold more effective than DEET at the same concentration. To translate these non-host assays to efficacy when used on the human host, we quantified repellency using a finger-climbing assay. TCA, nootkatone and DEET were equally effective in the fingertip assay, and patchouli oil was the only natural oil that significantly repelled ticks. CONCLUSIONS: The differences in repellent potency based on the assay type suggests that the ability to discover active tick repellents suitable for development may be more complicated than with other arthropod species; furthermore, the field delivery mechanism must be considered early in development to ensure translation to field efficacy. TCA, which is naturally derived, is a promising candidate for a tick repellent that has comparable repellency to commercialized tick repellents.

Effectiveness of lotilaner against ticks of the genus Amblyomma spp. in three naturally infested cane toads (Rhinella horribilis).

The efficacy of lotilaner was evaluated in three tick-infested cane toads. A single oral administration of lotilaner eliminated all ticks from all three toads from Day (D)1. Environmental samples collected from toad enclosures were negative for ticks until D30.

L'efficacité du lotilaner a été évaluée chez trois crapauds buffle infestés de tiques. Une seule administration orale de lotilaner a éliminé toutes les tiques des trois crapauds à partir du jour (J)1. Les échantillons environnementaux prélevés dans les enclos des crapauds étaient négatifs pour les tiques jusqu'à J30.

Se evaluó la eficacia de lotilaner en tres sapos de caña infestados por garrapatas. Una sola administración oral de lotilaner eliminó todas las garrapatas de los tres sapos desde el día (D) 1. Las muestras ambientales recolectadas de los recintos de sapos fueron negativas para garrapatas hasta el D30.

A eficácia do lotialaner foi avaliada em três sapos-boi infestados por carrapatos. Uma única administração de lotialaner eliminou todos os carrapatos de todos os sapos no Dia (D) 1. Amostras ambientais coletadas dos terrários dos sapos foram todas negativas para carrapatos até o D30.

Early onset of pre-lethal effects of lotilaner (Credelio®) on Amblyomma americanum ticks on experimentally infested dogs.

BACKGROUND: The speed with which acaricides paralyze and kill ticks is relevant to impeding pathogen transmission. The objective of this study was to assess early-onset lotilaner effects on the motility and weights of Amblyomma americanum ticks collected from treated dogs. METHODS: Twelve healthy dogs were randomized between two groups to receive either lotilaner (Credelio®) on Day 0 or to be sham treated. On Day 7, 25 male and 25 female A. americanum were placed under bandages, two on each flank of each dog. After 30 or 45 min, all unattached ticks were removed and T = 0 was set. At T = 2, 4, 8 and 24 h post attachment, 5 attached ticks removed from each bandage on each dog were weighed, assessed by blinded observers for righting ability and movement recorded. RESULTS: After the infestation period significantly fewer treated than control dogs had 20 ticks attached (50.0% versus 91.7%, P = 0.0015). At 24 h post attachment, mean weights of ticks from treated dogs (males 1.69 mg; females 2.72) were significantly less than ticks from controls (males 2.66 mg; females 4.67) (Pmale = 0.0002; Pfemale < 0.0001). Mean tick weights from the treated group were significantly lower at 24 h than at earlier time points (Pmale < 0.0307; Pfemale = 0.0021). At 4 and 8 h, significantly fewer ticks from treated (14.3%, 0.0%, respectively) than from control dogs could right (73.3%, 70.0%) (P4h < 0.0001; P8h = 0.0024) (at 24 h, all ticks from treated dogs were dead), and distance moved was significantly less at all time points (P2h = 0.0413; P4h, P8h < 0.0001). Mean and maximum velocity of ticks from treated dogs were significantly lower, relative to controls, at 4 and 8 h (P ≤ 0.0001). Within the treated group, collected ticks had significantly lower mean and maximum velocities at 4 and 8 h compared to 2 h (Pmean < 0.0042; Pmax < 0.0194). CONCLUSION: The observed changes indicate that lotilaner may disrupt tick attachment. In ticks that attached, a progressive impairment of neuromuscular processes began within 2 h. Those irreversible changes could substantially reduce the risk of pathogen transmission from tick to host.

Synthetic Pyrethroid, Natural Product, and Entomopathogenic Fungal Acaricide Product Formulations for Sustained Early Season Suppression of Host-Seeking Ixodes scapularis (Acari: Ixodidae) and Amblyomma americanum Nymphs.

We compared the ability of product formulations representing a synthetic pyrethroid acaricide (Talstar P Professional Insecticide), a natural product-based acaricide (Essentria IC3), and an entomopathogenic fungal acaricide (Met52 EC Bioinsecticide) to suppress Ixodes scapularis Say and Amblyomma americanum (L.) nymphs when applied following USEPA approved manufacturers' label recommendations for tick control using hand-pumped knapsack sprayers before the beginning of their seasonal activity period in the spring. We applied Met52 EC Bioinsecticide (11% Metarhizium anisopliae Strain F52) to five 100 m2 plots (10.6 ml AI/plot) in mid-April 2020. Two weeks later at the end of April 2020, we treated an additional five 100 m2 plots each with either Talstar P Professional Insecticide (7.9% bifenthrin @ 2.5 ml AI/plot) or Essentria IC3 (10% rosemary oil, 5% geraniol, and 2% peppermint oil @ 86.6 ml AI/plot). Weekly sampling of all plots through the end of June 2020 showed that both Met52 EC Bioinsecticide and Essentria IC3 failed to maintain a 90% suppression threshold for I. scapularis, compared to control plots, and required two additional applications over the course of the trial. In contrast, Talstar P Professional Insecticide suppressed 100% of I. scapularis nymphs and ≥96 and 100% of A. americanum nymphs and adults, respectively. Such pre-season applications of synthetic pyrethroids significantly reduce the early season acarological risk for exposure to host-seeking ticks as well as the frequency of acaricide applications.

Resistance of ticks on cattle to amitraz in Zimbabwe.

Resistance of one host and three host ticks on cattle to amitraz was studied using samples from five diptanks in the Domboshawa Communal Land Area of Zimbabwe. A random tick profile and a questionnaire survey on the tick control practices of the area were also carried out. Engorged Rhipicephalus (Boophilus) decoloratus, Rhipicephalus appendiculatus and Amblyomma hebraeum females were randomly collected from cattle presented for dipping at the 5 diptanks and were allowed to oviposit separately at T: 28 °C and RH: 85-95%. Larvae obtained were tested for resistance against various amitraz concentrations (1-0.0078125%) using the Larval Packet Test (LPT) and were compared with susceptible reference strains of R. (B.) decoloratus (Makuti strain, 2017), R. appendiculatus (Lake Chivero strain, 2015) and A. hebraeum (Lake Mutirikwi strain, 2017). The most abundant tick species were R. (B.) decoloratus (27.2%), Hyalomma rufipes (20.0%), H. truncatum (16.0%), R. appendiculatus (12.0%) and R. evertsi evertsi (11.9%). Amblyomma hebraeum (8.6%) and A. variegatum (1.8%) were the least common in the collection; this suggests that they were not well established in Domboshawa. Low amitraz resistance (RL = I) was detected only in R. (B.) decoloratus at 2 of the 5 diptanks. In the future, decentralised tick control due to inadequate and inconsistent supply of acaricides could introduce a number of factors which could contribute towards resistance development.

Chemical identification of Tagetes minuta Linnaeus (Asteraceae) essential oil and its acaricidal effect on ticks / Caracterização química e efeito acaricida do óleo essencial de Tagetes minuta Linnaeus (Asteraceae) em carrapatos

The control of tick species that affect animal production is vital for the economic welfare of the cattle industry. This study focused on testing the acaricidal activity of the essential oil from the leaves and stems of Tagetes minuta against several Brazilian tick species, including Rhipicephalus (Boophilus) microplus, Rhipicephalus sanguineus, Amblyomma cajennense and Argas miniatus. The chemical composition of the essential oil was determined by chromatography and spectroscopy analyses, which revealed the presence of monoterpenes. The adult immersion test (AIT) and the larval packet test (LPT) were used to evaluate the efficacy of T. minuta essential oil in tick management at concentrations of 2.5, 5, 10, 20 and 40%. The results demonstrated that the T. minuta essential oil had over 95% efficacy against four species of ticks at a concentration of 20%. These results suggest that the essential oil of T. minuta could be used as an environmentally friendly acaricide.(AU)

O controle de carrapatos que causa impacto na produção de bovinos possui importância econômica para a cadeia produtiva. Neste trabalho objetivou-se testar a atividade acaricida do óleo essencial das folhas e caules de Tagetes minuta contra várias espécies de carrapatos brasileiros, incluindo Rhipicephalus (Boophilus) microplus, Rhipicephalus sanguineus, Amblyomma cajennense e Argas miniatus. A composição química do óleo foi determinada por GC-MS e análises de espectroscopia de RMN, que revelaram a presença de monoterpenos. Na avaliação destas substâncias no controle do carrapato foram empregados os testes de imersão de adulto (TIA) e o de pacote de larvas (TPL) para o extrato de óleo de T. minuta nas concentrações de 2,5%; 5%; 10%; 20% e 40%. Os resultados do TPL e TIA demonstraram que o óleo essencial na concentração de 20% de T. minuta apresenta eficácia superior a 95% nas quatro espécies de carrapato. Estes resultados sugerem que o óleo essencial de T. minuta pode ser usado como um acaricida eficaz e com baixo impacto ambiental.(AU)