Interaction of Gulf Coast tick, Amblyomma maculatum Koch, nymphs on cattle
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Concern over the vector potential of the Gulf Coast tick, Amblyomma maculatum Koch, with the pathogen Ehrlichia ruminantium Dumler, causative agent of the disease heartwater, has increased the need for fundamental knowledge of tick ecology and behavior, specifically immature tick biology. Texas strain A. maculatum adult male ticks, known to emit attraction-aggregation-attachment pheromone (AAAP), were used to artificially simulate immature tick interaction with adults, in forced environments, on cattle. Artificial areas were grouped by treatment level, which were 1) aggregating, attached adult males, 2) aggregating attached adult females or 3) an empty area with no adults, as a control. Immature ticks were noted to be 6 times more likely to be aggregating in the AAAP treatment area when adult males were present. In the presences of either adult female ticks or no ticks at all, immature ticks were found to be attaching at random within the given area were they where permitted to feed. A second correlation of mortality was noted among immature ticks in the presence of AAAP emitting adult male ticks. In the permitted area where immature ticks could attach and feed, immature ticks were twice as likely to have survived to engorgement if adult male ticks were present in the area as well (53%). There was no difference in the survival rate among immature ticks if adult females were present or no adults at all, 26% and 21%, respectively. The study demonstrated that a significant attraction existed between immature ticks and attached adult males emitting AAAP.