Thesis

Central Pacific coast hard tick (Acari:Ixodidae): distribution, abundance, and Toxoplasma gondii prevalence

Toxoplasma gondii is a ubiquitous zoonotic protozoan parasite, whose infective and environmentally resistant oocyst stages can be transported into fresh and marine waters via freshwater runoff, stormwater discharge and sewer systems. The ingestion of these oocysts, either through direct consumption or through the consumption of filter-feeding marine bivalves, can have a detrimental impact on humans and a variety of marine mammals including the threatened southern sea otter (Enhydra lutris nereis). Terrestrial vertebrates are also susceptible to T. gondii infection since this parasite has a facultative heteroxenous life cycle that potentially includes all terrestrial vertebrates. Ticks (Acari) are known to serve as vectors for organisms that are pathogenic to humans and other animals, and it is suspected that ticks may serve as vectors for T. gondii and could facilitate transmission to terrestrial vertebrate hosts. This study evaluated the prevalence of T.gondii in populations of Pacific coast hard ticks (Dermacentor spp. and Ixodes spp.) and investigated the distribution and abundance of tick species in coastal terrestrial habitats. All ticks (n = 110) within the greater Morro Bay area, California tested negative for T. gondii. A significant difference was found between the number of flagged ticks at different sites and in different seasons. This study was the first to use DNA based analysis to attempt to detect T. gondii in Pacific coast hard ticks.

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