How do ticks move when seeking a meal?

A new study examines the question: How do ticks move when seeking a host? It’s well-known that ticks will sit-and-wait atop vegetation as they quest for their next meal, sitting with their front legs extended and grabbing onto a host passing by. “It is also known that ticks are willing to migrate horizontally (or actively search), when stimulated by the presence of host cues,” and that host-seeking behavior differs among life stages, writes Curtis and colleagues in the journal Medical and Veterinary Entomology. [1]

Understanding how ticks move is important in developing ways to minimize our risk of tick bites and infection. As the authors point out, “less is known about the distances adult ticks are willing and able to travel in the short term and when a host is in close proximity.”

The study looked at how adult ticks move on public trails that had “increasing levels of terrain complexity with a potential host nearby,” writes Curtis. The goal was to:

  1. Examine the extent to which adult ticks may actively search (vs. sit-and-wait) for a nearby host;
  2. Determine whether or not ticks could locate the position of the host in natural conditions;
  3. Determine the role of terrain complexity on the distance ticks traveled in a short period of time (30 min).

Observation Methods

Ticks were collected, marked with a painted dot, and returned to the observational area, which included 4 quadrants. The complexity of terrain increased for each quadrant. The observer (or potential host) was placed in 1 quadrant approximately 50 cm (1.5 feet) away from the tick.

The tick’s movement and questing behavior was observed every minute for half an hour. Questing was defined as “forelegs outstretched and waving.” The host was allowed to back away if the tick came within 10 cm.

Study Findings

“Overall, ticks were more often observed moving (72% of observations) than stationary (28% of observations).”

Two-thirds of ticks moved to the quadrant which contained the observer (host). In fact, “31 ticks (69%) were able to successfully move in the direction of the host in natural conditions.” The authors added, “it can thus be concluded that ticks spent a greater proportion of time in quadrant 1 (containing the host).”

Adult deer ticks will actively search for their next meal, rather than taking a sit-and-wait approach. Click To Tweet

Seven ticks (15.5%) reached the observer (host) within 30 minutes. The furthest distance the adult tick traveled towards the host was 110.5 cm (over 3 feet).

“Although ticks may indeed utilize a sit-and-wait strategy when no host is detected, this study suggests that adult I. scapularis ticks utilize an active-search strategy when a potential host is detected nearby,” Curtis writes.

Take Adult Ticks Seriously

The authors remind readers that:

  • Adult ticks are nearly twice as infected as nymphal ticks;
  • Adult ticks are seeking a host in the spring and fall compared to the summer for nymphal ticks;
  • Adult ticks can actively seek hosts as demonstrated in this study.

The host-seeking behavior was seen as a virtue by the authors. “Thus, patience is not always a virtue for host-seeking ticks – the transition to more of an active-search approach would likely increase the foraging success of ticks near host animals that have stopped to rest/sleep or feed.”

The authors granted that weather may have played a role. The study was conducted in dry conditions. Apparently, ticks prefer not to actively search when it’s raining or in wet vegetation.

“Ticks may be less likely to actively search when it is raining or vegetation has standing water as ticks avoid liquid water,” the authors write.

Public Awareness Important

Answering the question, “How do adult ticks move within various terrains?” is particularly important in adapting strategies to minimize the risk of tick bites and tick-borne infections.

For instance, “humans effectively reduce the complexity of terrain (by walking on, manicuring, trimming, landscaping, etc.), thereby promoting the horizontal movement of ticks and the likelihood of tick exposure in a short period of time.”

And individuals who engage in stationary outdoor activities, such as picnicking, napping, reading, are also at risk and should be aware that ticks may be present, actively moving and searching for a host.

“In addition, humans effectively reduce the complexity of terrain (by walking on, manicuring, trimming, landscaping, etc.), thereby promoting the horizontal movement of ticks and the likelihood of tick exposure in a short period of time.”

Note: The authors did not include nymphal ticks in their study. Researchers have assumed nymphal ticks take a wait and see approach and are susceptible to desiccation. Moreover, nymphal ticks are too small to observe using their study design.

References:
  1. Curtis TR, Shi M, Qiao X. Patience is not always a virtue: effects of terrain complexity on the host-seeking behaviour of adult blacklegged ticks, Ixodes scapularis, in the presence of a stationary host. Med Vet Entomol. 2020.
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