Amblyomma sculptum: identificação de alomônio em hospedeiro resistente (equus asinus) e olfatometria para candidatos à semioquímicos
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2017-12-21
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Universidade Federal de Goiás
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Amblyomma sculptum is a tick that has medical-veterinary importance and parasites a variety of hosts like capybaras, horses and humans. The tick control is a challenge due the disadvantages caused by conventional control so an alternative is desirable. Semiochemicals are potencial tools to be used once they modulate tick behavior and the use of pheromones, kairomones as well as the use of non-host species (allomones) to control ticks has already been demonstrated. Some semiochemicals have already been described in the literature that could act in A. sculptum behavior. It is also known that donkeys (Equus asinus) are more resistant to the parasitism of this tick specie than horses (Equus caballus). For this, four concentrations (10, 5, 2.5 and 1.25%) of 15 semiochemical candidates (CO2 only at 5%, benzaldehyde, benzoic acid, nonanoic acid, nonanal, salicylic acid, 2.6 diclorophenol, R-limonene, S-limonene, methyl salicylate, 1-octen-3-ol, acetone, ammonium hydroxide, isobutyric acid and lactic acid) were tested in non fed A. sculptum nymphs and adults using a Y-tube olfactometer. And here we investigated if donkeys could produce compounds that can act as repellent to A. sculptum. The CO2 was attractive to all stages tested. Nymphs were repelled by benzaldehyde and R-limonene both at 10% and isobutyric acid at 10 and 5%. Were attracted by methyl salicylate, benzoic acid and salicylic acid all at 1.25% and ammonium hydroxide at 2.5%. Males were attracted by benzoic acid at 2.5%. Females were repelled by benzaldehyde at 5%. Mixtures with the attractive compounds were done but no attraction was observed. The compounds that caused attractiveness in the olfactometer assay (CO2, methyl salicylate, benzoic acid, salicylic acid and ammonium hydroxide) were taken to the field and traps with these compounds were placed in a pasture naturally infested with A. sculptum ticks. The dry ice (CO2) is still the best substance to attract ticks in the field (p>0.05). To verify if non hosts produce repellents volatiles, odors from donkeys and horses were extracted from the dry sebum extract. So the compounds were identified by gas chromatography (GC) and coupled GC-mass spectrometry. Five main compounds were identified in both species being two predominant on horses: ethyl decanoate and ethyl octanoate, three predominant on donkeys hexanal, heptanal and trans-2-decenal. One compound trans-2-octenal occurring almost exclusively on donkeys was also identified and donkeys produced an average of 12,398 μg.mg-1. In olfactometer tests only the trans-2-octenal was repellent at different concentrations (10, 5, 2.5 and 1.25M). When an attractive substance (ammonium hydroxide) was added, the compound still repellent. The results indicated that benzoic acid should be further investigated since their results as attractant in laboratory and field. The isobutyric acid and R-limonene should be better exploited because of the repellent role presented in the behavioral test. And that the semiochemical identified here could be used to interfere in tick behavior and is therefore a potential compound to be transformed in a new technology to control A. sculptum.
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FERREIRA, Lorena Lopes. Amblyomma sculptum: identificação de alomônio em hospedeiro resistente (equus asinus) e olfatometria para candidatos à semioquímicos. 2017. 94 f. Tese (Doutorado em Ciência Animal) - Universidade Federal de Goiás, Goiânia, 2017.