Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Ticks, Tortoises and Tick-Borne Relapsing Fever in Mojave Desert Tortoise Habitat

Auteur : Bechtel, Molly June

Université de soutenance : Northern Arizona University

Grade : Doctor of Philosophy in Biology 2022

Résumé partiel
Argasid ticks, Ornithodoros parkeri and O. turicata occur throughout the Mojave Desert and are frequently observed on Mojave desert tortoises (Gopherus agassizii ; hereafter referred to as desert tortoise). These ticks harbor and transmit tick-borne relapsing fever (TBRF) group Borrelia, resulting in TBRF in people. Tick-borne relapsing fever group Borrelia is endemic in the western U.S. ; however, it is typically associated with the bite of an infected O. hermsi tick found in habitats at high elevations (above 1500 feet). This dissertation examines the relationship between O. parkeri and O. turicata, the TBRF group Borrelia species they carry, and their common host, the desert tortoise in Mojave desert tortoise habitat.

Chapter two of this dissertation described the first documented cases of TBRF in people associated with Ornithodoros ticks in the Mojave Desert. This case report described TBRF contracted by two tortoise biologists exposed to Ornithodoros ticks when excavating desert tortoise burrows in Clark County, Nevada. A blood sample from one of the cases was able to be sequenced to Borrelia turicatae, a TBRF group Borrelia carried by the tick O. turicata. This chapter emphasized the risk of TBRF for individuals, such as biologists working in Mojave desert tortoise habitat, desert tortoise pet owners, or anyone that interacts with desert tortoises and their burrows where Ornithodoros ticks are commonly encountered.

Despite the risk of contracting TBRF group Borrelia in Mojave desert tortoise habitat, limited research exists examining the relationships between O. parkeri and O. turicata and the desert tortoise. Chapter 3 of this dissertation examined this relationship using data collected from desert tortoise health assessments. As a threatened species, desert tortoise populations are monitored per U.S. Fish and Wildlife Services regulations and the health of individual tortoises is routinely assessed. Presence and abundance of ticks as well as clinical signs of disease and other morphometrics are collected for these health assessments. This chapter analyzed tick presence on desert tortoise health assessments as a function of season, location, sex, foraging behavior and evidence of clinical signs of disease. Ticks were more likely to be present on adult tortoises than juveniles and on captive tortoises versus wild tortoises. Ticks were also more likely to be observed on tortoises with observed clinical signs of disease and on tortoises without evidence of foraging. This analysis provided insight into the biology of ticks in relation to desert tortoises that may be useful for management of threatened tortoise populations where large tick infestations are detected and emphasized the risk of encountering ticks in tortoise burrows

Présentation et version intégrale (ProQuest)