Efficacy of spinosad against acaricide-resistant and -susceptible Rhipicephalus (Boophilus) microplus and acaricide-susceptible Amblyomma americanum and Dermacentor variabilis

Effect of the combination of DEET and flupyradifurone on the tick Ixodes ricinus: Repellency bioassay and pharmacological characterization using microtransplantation of synganglion membranes

Ticks are vectors of many human and animal pathogens, and represent a major threat to public health. In recent years, an increase in tick-borne diseases has been observed, and new strategies are therefore needed in order to control tick numbers and reduce human tick bites. In the present study, we adapted the previous tick repellency bioassay based on the exploration behavior of the tick, using the ToxTrac software and video-tracking, to compare the repellent effect of two compounds on the tick Ixodes ricinus: N,N-diethyl-methyl-m-toluamide (DEET), and butenolide, flupyradifurone (FLU). We found that when applied alone, 10% DEET or FLU have no/or low repellency effect. But, the combination of both 10% DEET and FLU demonstrated a significant repellency effect against I. ricinus, similar to the repellency of 20% DEET. Using membrane microtransplantation, we evaluated the effect of DEET and FLU on native acetylcholine receptors expressed on the tick synganglion. We found that DEET has no effect on acetylcholine-evoked currents, but significantly reduced nicotine-induced current amplitudes. FLU induced an ionic current but was not able to reduce acetylcholine or nicotine evoked currents. The combination of both DEET and FLU strongly reduced nicotine-evoked currents. Finally, we demonstrated that our recording device for repellency, as well as the use of membrane microtransplantation, could be used as methods to study the mode of action of active compounds on ticks.

Interaction between anti-tick vaccine and a macrocyclic lactone improves acaricidal efficacy against Rhipicephalus (Boophilus) microplus (Canestrini) (Acari: Ixodidae) in experimentally infested cattle

The southern cattle fever tick (SCFT) Rhipicephalus (Boophilus) microplus, is considered the most important ectoparasite of livestock in the world because of high financial losses associated with direct feeding and transmission of the hemoparasites Babesia bovis, B. bigemina, and Anaplasma marginale. Unfortunately, SCFT in many parts of the world have evolved resistance to all market-available pesticides thus driving development of new control technologies. Vaccination against ticks using the tick gut protein Bm86 has been shown to be effective against acaricide-resistant ticks. This technique has been successfully implemented in Puerto Rico for the control of acaricide-resistant R. microplus on dairy and beef cattle. Observations from Puerto Rico indicate a potentially positive interaction between anti-tick vaccination when used in conjunction with systemic acaricide treatment. In this project, controlled animal studies were completed directly comparing efficacy of anti-tick vaccination with and without systemic acaricide. Results show that the Bm86 anti-tick vaccine in combination with the macrocyclic lactone, Moxidectin, expressed a synergistic interaction, providing greater and longer efficacy than either treatment alone.

Control of Tick Infestations in Oryctolagus cuniculus (Lagomorpha: Leporidae) With Spinosad Under Laboratory and Field Conditions

Because of great economic loss in the world's livestock industry, and the serious risks to human health, the control of ticks and tick-borne diseases is one of the most important health management issues today. Current methodology involves integrated tick control for preventing the development of resistance. Rabbits are hosts for immature stages of the three-host tick Hyalomma lusitanicum Koch; so, we focus on this host as a strategy to interrupt the tick life cycle. Spinosad is an insecticide-acaricide, produced by the fermentation of metabolites of the actinomycete bacterium Saccharopolyspora spinosa. We administered spinosad orally by force-feeding naturally and artificially infested rabbits, and under field conditions by administering treated food via a hopper during the period of peak infestation and reinfestation risk for rabbits. No living larvae were recovered from treated laboratory rabbits. In naturally infested rabbits, the number of live ticks collected from treated rabbits (mean = 0.62 ticks per ear) was significantly lower than those recovered from untreated rabbits (mean = 7.27; P < 0.001), whereas the number of dead ticks collected from untreated rabbits (mean = 6.53) was significantly lower than those recovered from treated rabbits (mean = 18.62; P < 0.001). In addition, free and continually reinfested rabbits freely ingested low doses of spinosad, reducing the tick burden from 48.00 (Day 0) to 26.09 ticks per ear in treated rabbits (Day 16), whereas controls maintained the infection (46.64). This strategy could be useful as an alternative or supplement to traditional acaricides in tick control programs.