Robotic Control of Tick Populations

Tick-borne diseases are becoming increasingly common in the United States, including Lyme, Rocky Mountain spotted fever, ehrlichiosis, and babesiosis. Their increase in infection rates closely tracks a rise in the geographic area of infected ticks, prompting interest in new methods of tick population control. The most common existing method involves spraying the environment with permethrin, which, although highly effective, also poisons fish, fowl, bees, and other wildlife. This paper describes a novel robotic method designed to reduce tick populations without the associated environmental toxicity of chemical spraying. It employs a robot that follows a wire emitting a magnetic signal beacon around the perimeter of a property while dispensing a chemoattractant. The magnetic signal is generated by a small battery-run constant-current frequency generator. The robot's steering is controlled by proportional-integral controllers that compare the magnetic signal detected by left and right side resonant inductors mounted on the robot, and its forward speed is controlled by a second proportional integral controller calibrated to move the robot at the speed of a slow walk. A chemoattractant, such as CO
₂
, is released by the robot, which, with the vibration associated with the robot's movement, establishes the biomimicry necessary to cause the tick to latch onto the robot's fabric-covered drag mat and wings. The fabric is infused with permethrin, killing the ticks in seconds while leaving virtually no trace of the chemical in the environment. An early prototype of the robot showed it acutely reduced tick populations by 88% ± 10% after 5 passes, but 48 hours after treatment the population returned to approximately pre-treatment levels. This was hypothesized to occur because only a percentage of ticks emerge from stasis on any given day to feed, but the early prototype robot proved unreliable and difficult to use for repeated-day operation needed to test this theory. The robot described in this paper incorporates a number of changes to allow multi-day testing including improved steering algorithms, water-resistant electronics, a manual mode to allow the user to remotely pilot the vehicle back on track should it lose tracking in a tight turn, and multiple indicators to assist debugging in the field. This will enable time-longitudinal studies of the robot's effects on tick population reduction planned by researchers in the summer of 2020 and may ultimately lead to a new method for tick population control.