In vitro assays for repellents and deterrents for ticks: differing effects of products when tested with attractant or arrestment stimuli

Abstract

Abstract. Most in vivo and in vitro tests with repellents or deterrents against ticks have not considered which sensory channel is being targeted. We have recorded the responses of two hard tick species (Acari: Ixodidae) in vitro to determine if such products can disrupt the perception of an attractant in a repellent assay or the perception of an arrestment stimulus in a deterrent assay. Ethyl butylacetylaminopropionate (EBAAP), N,N-diethyl-methyl-benzamide (deet), permethrin and indalone were chosen to test their capacity to inhibit the attraction of Amblyomma variegatum Fabricius to its aggregation-attachment pheromone. Vapours of each test product plus those from a synthetic blend of the pheromone were delivered to the walking tick in an air stream on a locomotion compensator. Neither EBAAP, deet, permethrin nor indalone could inhibit attraction of A. variegatum even when each of the test products was delivered at 10 6 times the pheromone. Indalone did decrease the attraction of A. variegatum to the pheromone and induced repulsion of A. variegatum when presented on its own in the air stream. The effect of permethrin, a sodium channel blocker, was also tested in a deterrent assay measuring the arrestment of Ixodes ricinus (L.) adults on its own faeces and faecal constituents. Permethrin deterred arrestment at doses of 670 fg/cm 2 to 67 ng/cm 2 , i.e. at levels five times lower than the dose of chemostimuli present in the arrestment stimulus. This sensitivity to permethrin suggests that it acts via the contact chemoreception channel.

Repellent activity of DEET against Amblyomma cajennense (Acari: Ixodidae) nymphs submitted to different laboratory bioassays

“…Salafsky et al (2000) observed only partial repellency of A. americanum adults using commercial 20% DEET formulations and no protection against Dermacentor variabilis Say. The compound did not repel Amblyomma variegatum Fabricius adults when released with an attractant stimulus (MCMAHON et al, 2003). Based on the results of the present study and on the literature it is clear that A. cajennense is more sensitive to DEET than other tick species so far evaluated.…”

Identification of non-host semiochemicals for the brown dog tick, Rhipicephalus sanguineus sensu lato (Acari: Ixodidae), from tick-resistant beagles, Canis lupus familiaris

“…The results observed in the Petri-dish assays may have been due to deterrence, but were also possibly due to the repellent properties of the compounds tested (Ferreira et al, 2001;McMahon et al, 2003). On the other hand, in the olfactometer, arthropods are guided by anaemotactic stimuli, directly influenced by the presence of chemicals in the vapour phase (Ferreira et al, 2001;McMahon et al, 2003;Vilela and Lucia, 2001), thus confirming the repellent property of the compounds.…”

“…On the other hand, in the olfactometer, arthropods are guided by anaemotactic stimuli, directly influenced by the presence of chemicals in the vapour phase (Ferreira et al, 2001;McMahon et al, 2003;Vilela and Lucia, 2001), thus confirming the repellent property of the compounds. It is noteworthy that the percentage of repellency observed in the Y-tube olfactometer using the 2-hexanone:benzaldehyde mixture was similar to that observed by Louly et al (2010) when testing crude beagle extracts.…”

Olfaction in vector-host interactions

“…Similarly Dautel et al (1999) reported that I. ricinus nymphs would not contact DEET-treated filter paper. McMahon et al (2003) reported that indalone in an airstream caused A. variegatum to walk downwind, however airborne DEET did not repel ticks attracted to the AAA pheromone. Permethrin, while a toxicant, also repels a range of tick species and is used for treatment of military uniforms (Mehlhorn et al 2003, McCain and Leach 2007, Schreck et al 1995.…”