ALOMONES FOR CONTROL OF IXODID TICKS

Resumen

Recently; the presence of the allomones; 2-hexanone and benzaldehyde; was observed in the odours of dogs resistant to the tick Rhipicephalus sanguineus sensu lato (s.l.). These compounds were added in slow release formulations on dogs’ collars and they decreased in up to 50% the tick load of dogs exposed to walls artificially infested with R. sanguineus. To improve the efficacy of R. sanguineus s.l. control; we are evaluating the push-pull strategy using an arrestment pheromone associated with the fungus Metarhizium anisopliae; for application on the environment; and the repellent collars for use on infested dogs. Behavioural bioassays conducted in Petri plates demonstrated the presence of arrestment pheromone on extracts of exuviae and excreta from R. sanguineus s.l. Tests with compounds isolated in arrestment pheromones of ixodid ticks; such as guanine; xanthine and uric acid; alone or combined; are been conducted and so far; arrestment to 1% xanthine and 0.01% guanine were observed. The repellents are been tested on dogs naturally infested with R. sanguineus s.l. Two groups (control and treated) with 30 dogs each; were performed: - fifteen dogs in each group were evaluated so far; and the adult’s burden was decreased in the treated group for up to one month. Based on the knowledge that resistant dogs produce allomones; the presence of repellents has been evaluated in the sebum of donkeys; which is a species naturally resistant to the tick Amblyomma sculptum. When comparing the compounds present in the sebum of equines – a species susceptible to A. sculptum - with the sebum of donkeys; we identified a donkey-exclusive compound; (E)-2-decenal; which was repellent to A. sculptum nymphs in an olfactometer. Tests performed to develop a formulation based on this repellent for use in humans are demonstrating its efficacy.