Chemosensory and Behavioural Responses of Ixodes scapularis to Natural Products: Role of Chemosensory Organs in Volatile Detection

Abstract

Blacklegged ticks, Ixodes scapularis, represent a significant public health concern due to their vectoring of tick-borne disease. Despite their medical importance, there is still limited knowledge of the chemosensory system of this species, and thus a poor understanding of host-seeking behaviour and chemical ecology. We investigated the electrophysiological sensitivity of adult female blacklegged ticks to attractants and plant-derived compounds via an electrode inserted into the scutum. The response of female ticks to binary mixtures with a constant concentration of a selected attractant (butyric acid) and increasing concentration of volatile organic compounds (VOCs) (geraniol, phenethyl alcohol, β-citronellol, and citral) was recorded. A strict relationship between increasing volatile concentration and a decreasing response was observed for each VOC. Y-tube bioassays confirmed that tick attraction towards butyric acid decreased with the presence of a VOC, which exerted a deterrent effect. To determine the specific role of sensory appendages involved in the detection of attractant chemical stimuli, we tested tick electrophysiological response after removing appendages that house chemosensory sensilla (foretarsi, pedipalps, or both). The chemosensory response was related to the molecular structure of attractant odorant, and the lack of pedipalps significantly reduced olfactory responses, suggesting they play an important role in detecting attractants. This study provides new insight into the neurophysiological mechanisms underlying tick olfaction and the potential for interactions between attractant and deterrent chemical detection.

Spatial repellents transfluthrin and metofluthrin affect the behavior of Dermacentor variabilis, Amblyomma americanum, and Ixodes scapularis in an in vitro vertical climb assay

“…It is comprised of two major structures: an anterior pit that detects humidity and a capsule fitted with host-cue sensing, physiologically diverse olfactosensilla. The response to repellents, including DEET, has been shown to diminish with the occlusion or surgical removal of the Haller’s Organ, suggesting that the Haller’s Organ plays a role in the repellent response [ 60 , 63 ]. Conversely, ticks have shown equal response to other repellents including phenethyl alcohol (PEA) with the Haller’s Organ removed–alluding to other structures playing important roles in repellent chemoreception [ 63 ].…”

Synthesis and Characterization of β-Cyclodextrin-Essential Oil Inclusion Complexes for Tick Repellent Development

“…Among the selected EOs, GE was the most effective, repelling up to 90% of tested ticks. The ability of ticks to detect the main component of GE essential oil (i.e., β-citronellol) was previously reported [ 39 ] which has excellent tick repellent properties [ 14 ], and the encapsulation in the cyclodextrin cavity may have improved efficacy and longevity of this effective active ingredient. Interestingly, the GE complex prepared using method 2 was highly effective, while the GE complex from method 1 repelled only 70% of tested ticks.…”

“…Recent studies have focused on testing repellents against mosquitos, but not much attention has been devoted on testing polymer based-products against ticks [ 44 , 45 , 47 , 48 ], which present a different chemosensory system that may be impacted differently by the encapsulation of active ingredients. [ 39 ]. In this study, the production of EO ICs has been performed on a laboratory scale.…”

A new paradigm for personal protection against ticks: efficacy of spatial repellents to reduce host seeking activities in three major tick species of medical importance

“…It is also used in personal protection as a clothing treatment for long-lasting tick protection through acaricidal action, with little signs of repellency [12]. The lack of a standardized method for evaluating non-lethal, behavior modifications in ticks stems from an incomplete understanding of tick olfaction at the molecular level and lack of defined actions in the host-seeking and feeding process [13]. Ticks are relatively slow moving, do not fly, and may spend days attached to a host, making repellency efforts difficult to quantify.…”