Abstracts Category : Other

Off-host biology and ecology of immature Gulf Coast ticks (<i>Amblyomma maculatum</i> Koch) in Mississippi

by III Jos Portugal

Little is understood about off-host behavior and ecology of immature <i>Amblyomma maculatum</i> Koch (Gulf Coast tick). A more complete understanding of this tick is essential to protect human and animal health. My research focused on seasonality and distribution of immatures in Mississippi, potential suitability of some insect and human hosts to larvae, and aspects of nymphal questing behavior. A single larva was collected (third off-host collection reported) when sampling <i>A. maculatum</i> habitat using a novel device. Collection of this larva in November expands the stages known seasonality and confirmed a prediction concerning seasonality of larval <i>A. maculatum</i>. Low frequency of immatures (8.3%) confirmed that theyre incredibly difficult to collect off-host. Nymphal collections peaked in March, and known seasonality was extended for both nymphs and adults. I examined known records, elucidating seasonality and distribution of <i>A. maculatum</i> in Mississippi. Either multiple generations per year or diapause are responsible for observed bi-modal distribution of immature collections. Additionally, Icompiled the most extensive host record of immature <i>A. maculatum</i> in Mississippi and investigated seasonality patterns using USDA plant hardiness zones. I compiled the most complete record of ticks found on arthropods. <i>Amblyomma americanum</i> and <i>A. maculatum</i> were both confirmed to crawl onto arthropods, giving support to occasional, unintentional dispersal by phoresy. There was no conclusive evidence that larval <i>A. maculatum</i> feed on arthropods, however data supported feeding by larval <i>A. americanum</i>. These results have interesting implications regarding evolution of pathogens/endosymbionts. I provided the first evidence that larval <i>A. maculatum</i> can attach to humans. <i>Rickettsia parkeri</i>, a human pathogen transmitted by this species has recently been shown to be capable of transovarial transmission. Therefore, larval <i>A. maculatum</i> may provide another avenue of transmission. I have demonstrated that <i>A. maculatum</i> are difficult to collect off-host in part because they prefer to quest low to the ground. In choice studies, 5-cm-tall stems were most likely to be occupied by nymphs released into an array of stems. Low vapor pressure deficit encouraged questing, while higher VPD and warmer temperature increased questing height. These results may have implications in understanding host-seeking behavior in other tick species as well. Advisors/Committee Members: Jerome Goddard, Ph.D. (chair), Andrea S. Varela-Stokes, D.V.M, Ph.D. (committee member), Gerald T. Baker, Ph.D. (committee member), Jeffrey W. Harris, Ph.D. (committee member), John C. Schneider, Ph.D. (committee member).