D3006: Tick terrains: Unraveling how geography shapes the questing strategies of western black-legged ticks

Vector-borne zoonotic diseases are emerging, partly due to increased human-vector interactions. Human encounters with infected blood meal-seeking vectors can result in pathogen transmission. This interaction has resulted in highly reported cases of diseases such as Lyme disease (LD) (a disease caused by the bacteria, Borrelia burgdorferi). Host-seeking behavior is a critical component of human risk of encountering and being bitten by a tick but the factors that shape tick behavior are not well resolved. Infection with a pathogen can lead to behavioral alterations of the vector and has been documented in other vector species, resulting in increased biting rates, longer biting times, more time spent host-seeking, and increased movement. These behavioral modifications may promote pathogen transmission, however, the impact of B. burgdorferi on tick questing behavior is unknown but could have important implications for pathogen transmission cycles. In addition, the role of geographic and environmental factors on host-seeking behavior in ticks is also understudied. Here, we examined the influence of both B. burgdorferi infection and geographic origin on I. pacificus questing behavior. We collected nymphal ticks from three distinct geographical locations in California that span a large latitudinal range and measured tick questing behavior (e.g. climbing and mobility). Our results show evidence of geographical structuring on I. pacificus activity and behavior, suggesting that ticks from southern California exhibit higher questing activity compared to northern populations. These results advance the understanding of the determinants of I. pacificus nymphal questing behavior and help explain the spatial distribution in Lyme disease cases.