Quantification of brown dog tick repellents, 2-hexanone and benzaldehyde, and release from tick-resistant beagles, Canis lupus familiaris

Abstract

We have recently shown that repellency of the tick Rhipicephalus sanguineus sensu lato by the tick resistant dog breed, the beagle, is mediated by volatile organic compounds (VOCs) 2-hexanone and benzaldehyde present in beagle odour. Ectoparasite location of animal hosts is affected by variation in these odour components and their ratios. The aim of this study was to quantify the release rate, and the ratio, of 2-hexanone and benzaldehyde from beagles. The odour of three beagles was collected, for four days, over one week (day 0, day 1, day 4 and day 7). The compounds were identified using coupled high-resolution gas chromatography-mass spectrometry (GC-MS), and authentic standards of compounds were used to generate external calibration curves for quantification. Both compounds were found in all dogs on all days. The amount of benzaldehyde was always higher than that of 2-hexanone and so their ratio varied from unity, on average (over time) being 3.128±0.365, 1.902±0.390, 1.670±0.671ngmL(-1) for beagle 1, 2 and 3, respectively. There was no significant (p<0.05, F-test) effect of time. The overall mean was 2.233±0.387ngmL(-1). These results further previous findings by documenting the presence of 2-hexanone and benzaldehyde in beagle odour samples covering a 7-day period. This knowledge enables development of repellents to protect dogs from R. sanguineus s. l. infestation.

Towards a new phenotype for tick resistance in beef and dairy cattle: a review

“…comm.). Similar results have been reported for differential attractiveness of different dog breeds to ticks (Borges et al 2015;de Oliveira Filho et al 2016, with the same hypothesis of differential volatile signalling testing true, albeit the repellents that were identified were different from those in cattle.…”

Brown dog tick, Rhipicephalus sanguineus sensu lato, infestation of susceptible dog hosts is reduced by slow release of semiochemicals from a less susceptible host

“…Our subsequent work identified two volatile small lipophilic molecules(SLMs), 2-hexanone and benzaldehyde,which are produced in greater amounts in beagles,and which act as natural 4 4 repellents against R. sanguineuss. l. (Borges et al, 2015), and demonstrated constitutive release of these two SLMs in the odor of beagles (Oliveira Filho et al, 2016).…”

“…The oven temperature was maintained at 30 o C for 0.1 min, then programmed at 10 o C min −1 to 250 o C and held for 30 min. The quantity of compound captured per sample was expressed in µg/day using the analytical method described by Oliveira-Filho et al (2016). For 15 days, the release rates were 30.44 ± 1.12 µg/day for benzaldehyde and 14.38 ± 1.26 µg/day for 2-hexanone, decreasing sharply to 11.18 µg/day and 1.29 µg/day, respectively, after the 7 th day.…”

Cattle Tick Rhipicephalus microplus-Host Interface: A Review of Resistant and Susceptible Host Responses

“…Although a few studies have demonstrated that host VOCs play a role in attracting Rhipicephalus spp. ticks (Louly et al, 2010 ; Borges et al, 2015 ; de Oliveira Filho et al, 2016 ; Franzin et al, 2017 ), research is still needed to investigate the interrelationship of host microbiota with VOC production related with tick attraction or repulsion. This may potentially reveal yet other factors contributing to tick susceptibility thereby presenting new opportunities to develop control methods for the livestock ectoparasite, R. microplus .…”