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Previously, 4-methylguaiacol, a major constituent of cattle anal odour, was found to have a high repellence on Rhipicephalus appendiculatus. In the present study, 10 structural analogues of the phenol were tested for repellence against R. appendiculatus in order to assess the effects of (i) absence or presence of the 4-alkyl group of varying length, (ii) inclusion of a double bond in the 4-alkyl chain, (iii) linking the two phenolic oxygen in a methylenedioxy bridge, (iv) replacement of the OCH 3 with CH 3 and inclusion of another CH 3 at position 6, and (v) presence of an additional OCH 3 group at position 6. The analogues comprised of 2-methoxyphenol (guaiacol), 4-ethyl-2methoxyphenol, 4-propyl-2-methoxyphenol, 4-allyl-2-methoxyphenol (eugenol), 3,4-methylenedioxytoluene, 2,4dimethylphenol, 4-ethyl-2-methylphenol, 2,4,6-trimethylphenol, 4-propyl-2,6-dimethoxy-phenol and 4-allyl-2,6dimethoxyphenol, which were compared at different doses in a two-choice climbing assay set up. Each analogue showed either increased or reduced repellence compared with 4-methylguaiacol. The structural feature that was associated with the highest repellence was 4-propyl moiety in the guaiacol unit (RD 75 = 0.031 for 4-propyl-2methoxyphenol; that of 4-methylguaiacol = 0.564). Effects of blending selected analogues with high repellence were also compared. However, none of the blends showed incremental increase in repellence compared with that of 4propyl-2-methoxyphenol. We are currently evaluating the effects of controlled release of the compound at different sites on cattle on the behavior and success of R. appendiculatus to locate their predilection feeding site.

Previously, 4-methylguaiacol, a major constituent of cattle anal odour, was found to have a high repellence onRhipicephalus appendiculatus. In the present study, 10 structural analogues of the phenol were tested for repellence against R. appendiculatus in order to assess the effects of (i) absence or presence of the 4-alkyl group of varying length, (ii) inclusion of a double bond in the 4-alkyl chain, (iii) linking the two phenolic oxygen in a methylenedioxy bridge, (iv) replacement of the OCH 3 with CH 3 and inclusion of another CH 3 at position 6, and (v) presence of an additional OCH 3 group at position 6. The analogues comprised of 2-methoxyphenol (guaiacol), 4-ethyl-2methoxyphenol, 4-propyl-2-methoxyphenol, 4-allyl-2-methoxyphenol (eugenol), 3,4-methylenedioxytoluene, 2,4dimethylphenol, 4-ethyl-2-methylphenol, 2,4,6-trimethylphenol, 4-propyl-2,6-dimethoxy-phenol and 4-allyl-2,6dimethoxyphenol, which were compared at different doses in a two-choice climbing assay set up. Each analogue showed either increased or reduced repellence compared with 4-methylguaiacol. The structural feature that was associated with the highest repellence was 4-propyl moiety in the guaiacol unit (RD 75 = 0.031 for 4-propyl-2methoxyphenol; that of 4-methylguaiacol = 0.564). Effects of blending selected analogues with high repellence were also compared. However, none of the blends showed incremental increase in repellence compared with that of 4propyl-2-methoxyphenol. We are currently evaluating the effects of controlled release of the compound at different sites on cattle on the behavior and success of R. appendiculatus to locate their predilection feeding site.

We previously identified 4-propylguaiacol to be a highly potent repellent against Rhipicephalus appendiculatus, which transmits East Coast Fever in cattle. So far, the major method that has been employed for tick control is the use of acaricides, which so far has posed a number of challenges. Encapsulation technology may offer a long-term solution to the existing problems by dispensing the repellent at a controlled rate. 4-Propylguaiacol was encapsulated in various nanoparticles, which included β-cyclodextrin, ethyl cellulose, and polyvinylpyrrolidone. The inclusion of 4-propyl guaiacol in the resulting complexes was confirmed by FT-IR, XRD, and SEM analysis. All the sharp peaks belonging to each of the encapsulating polymers were observed. However, some of the characteristic peaks of 4-propylguaiacol disappeared in the complex formed. The rates and duration of release of 4-propylguaiacol from 0.2 g of each inclusion complex were then compared at 38–40°C every 3 hours for 24 hrs. The observed rates of release for 4-propylguaiacol were 0.396 mg/hr., 0.632 mg/hr., and 0.648 mg/hr. Rate from β-cyclodextrin, ethyl cellulose, and PVP inclusion complexes, respectively. The release rate of 4-propylguaiacol in the β-cyclodextrin complex was more controlled than it was in ethyl cellulose and PVP complexes. This controlled release rate exhibited by the β-cyclodextrin complex in small doses for a relatively long time provides a potential tool for dispensing repellents on cattle to protect them from tick bites.