Geotropic, hydrokinetic and random walking differ between sympatric tick species: the deer tick Ixodes scapularis and the lone star tick Ambylomma americanum

Spatial and temporal activity patterns of Amblyomma americanum

BACKGROUND

Estimates of tick abundance and distribution are used to determine the risk of tick-host contact. Tick surveys provide estimates of distributions and relative abundance for species that remain stationary and wait for passing hosts (i.e. questing), but measures of tick populations may be less reliable for species that actively move in search of a host, such as Amblyomma americanum, the lone star tick (LST). Risk estimates for contact with adult LST require knowledge of the tick's spatial and temporal activity. Understanding the movement and the temporal patterns of host-seeking behavior will enhance risk assessment for LST.

METHODS

Using CO2-baited traps over a 2-year period, we collected wild adult LST in Oklahoma. We used mark-recapture techniques to determine the distance ticks will travel, the proportion of the tick population that is detectable over time, and the relationship between tick abundance and the number of ticks detected in the field. Using video tracking software, we measured the distance traveled and activity time in the laboratory.

RESULTS

In 24 h, LST travel up to 9 (mean = 3.2, SD = 3.6) m in the field and 36 (mean = 70.4, SD = 81.0) m in the laboratory. Marked LST were detectable in the environment for up to 14 days after release. We found that the number of recaptured ticks significantly increased with the relative abundance of ticks released, and at a minimum abundance (N = 1 tick released) LST were detectable 33.3% of the time. Across all experiments, fewer than half of marked ticks were recovered and at most 28.4% of ticks were detected with CO2-baited traps at any given time.

CONCLUSIONS

Our results show that LST actively move through the environment and pose a risk for host contact at distances of tens of meters. Ticks are detectable for several weeks, but only a fraction of them are detectable at any time. Larger numbers of ticks are detected as their population size increases, but even at very low numbers, LST are recovered with CO2 baiting. These spatial and temporal aspects of LST behavior should be considered when building predictive risk models of LST-host contact.

Behavior of Nymphs and Adults of the Black-Legged Tick Ixodes scapularis and the Lone Star Tick Ambylomma americanum in Response to Thermal Stimuli

Ticks use chemical and thermal signals emitted by humans and other vertebrates to locate suitable hosts for a blood meal. Here, we study the behavior of black-legged Ixodes scapularis and the lone star ticks Amblyomma americanum exposed to heat sources held at temperatures near those of vertebrate hosts (32 °C). First, we used a locomotion compensator to test behavioral responses of ticks to an infrared light emitting diode (LED). The servosphere allowed us to measure parameters such as velocity, acceleration, linearity, and orientation. Then a heating element (Peltier) located in one of the extremes of a double-choice vertical rod (flying T), was employed to observe upward movement of the ticks toward such a heat source. While both species oriented toward the LED, only lone star ticks were attracted to the Peltier element while climbing upward. In conclusion, we showed that heat attracted ticks from short distances up to several centimeters on a the servosphere, and those responses differed between the two species of ticks on the flying T. We discuss our results in the context of the ecology of both tick species and their potential in tick survey and management.