salicylates and Tick-Infestations

The responses of adult Amblyomma variegatum ticks released from various distances to different doses of the synthetic attraction-aggregation-attachment pheromone (AAAP) (made up of orthonitrophenol, methyl salicylate and nonanoic acid in paraffin oil), dispensed from the center of circular field plots, were studied in the presence or absence of elevated levels of CO2. Up to 90% of the ticks released were attracted to the pheromone source in the presence of CO2 within 3h. CO2 alone was unattractive, similar to previous findings in Zimbabwe, but unlike results from a Caribbean A. variegatum population, which was significantly attracted to this signal. In the absence of CO2, smaller but significant proportions of the released ticks were attracted to the pheromone, albeit more slowly, suggesting another variation in the responses of this bont tick to inter- and intra-specific signals. Our results are interpreted in the light of a study undertaken elsewhere demonstrating relatively high heterozygosity among tick populations. Possible directions of further research to explore the use of the pheromone in off-host control of the tick are also highlighted.

Topics: Animals; Carbon Dioxide; Female; Ixodidae; Kenya; Male; Nitrophenols; Pheromones; Salicylates; Tick Infestations

Three low molecular weight compounds were found in hexane:diethyl ether extracts of fed males of the African ticks, Amblyomma variegatum (tropical bont tick) and A. hebraeum (bont tick), namely, o-nitrophenol, methyl salicylate and 2,6-dichlorophenol. These same compounds were also fond in a rinse of fed A. variegatum males, but were absent or present in only trace amounts in a rinse of fed A. hebraeum males, o-Nitrophenol and methyl salicylate were present in much higher concentrations (i.e., amounts/tick) in A. variegatum than in A. hebraeum. 2,6-Dichlorophenol was also more abundant in A. variegatum than in A. hebraeum, but the differences were not as great as with the former two compounds. Extraction in hexane over a 3-week period revealed four additional compounds, benzaldehyde, benzyl alcohol, benzothiazole and nonanoic acid. The first three compounds were found in males of both species; nonanoic acid was found only in A. hebraeum males. Published reports consistently show strong attraction by o-nitrophenol and methyl salicylate for both sexes of the two bont tick species; 2,6-dichlorophenol and benzaldehyde have been reported to be attractive to both sexes of A. hebraeum. The possible roles of these compounds, as well as others occasionally reported from A. hebraeum and A. variegatum, as components of the aggregation/attachment pheromone or other pheromones is discussed.

Topics: Animals; Arachnid Vectors; Benzaldehydes; Benzothiazoles; Benzyl Alcohol; Benzyl Alcohols; Chlorophenols; Chromatography, Gas; Fatty Acids; Feeding Behavior; Female; Gas Chromatography-Mass Spectrometry; Heartwater Disease; Male; Nitrophenols; Salicylates; Sex Attractants; Sexual Behavior, Animal; Thiazoles; Tick Infestations; Ticks