Shelters often make euthanasia or adoption decisions based on the results of FeLV-FIV point-of-care tests but given the low estimated prevalence of these diseases and imperfect test performance, this might not be a good practice because of diagnostic error. The objectives of this study were to determine the true prevalence of FeLV and FIV in apparently healthy and sick shelter cats in Mississippi, estimate predictive value of the Zoetis Witness FeLV-FIV Rapid ImmunoMigration test results at the estimated true prevalences through Bayesian latent class modeling, and formulate testing recommendations for shelters. One chapter will review the literature on FeLV and FIV. The bulk of this thesis will focus on determining the true prevalence of retroviral infection in Mississippi shelter cat populations. The last chapter will use Bayesian modeling to estimate test performance and predictive value of test results in healthy and sick shelter cat populations.

To increase capacity for monitoring and surveillance of tick-borne diseases, publicly available tick distribution and climate change datasets are required to create accurate predictive distribution models. It is difficult, however, to assess model accuracy and utility when using incomplete datasets.  The more recent development of comprehensive tick databases for Europe and availability of climate change scenarios from multiple IPCC Assessment Reports allows for improved modeling efforts. Multiple tick datasets were combined and three climate change projections were compared by predicting current and future distributions of Ixodes ricinus ticks in Europe using the MaxEnt species distribution model. Overall, much of Europe contains suitable habitat for the Ixodes ricinus tick, both now and under future climate change projections.  Contraction of habitable areas is predicted to occur at lower latitudes and altitudes, while expansion is predicted to occur at higher altitudes in mountainous regions and the higher latitudes, primarily in northern Scandinavia.

Human body lice, Pediculus humanus humanus, and head lice, Pediculus humanus capitis, have been hematophagous ectoparasites of humans for thousands of years. Despite being ecotypes, only body lice are known to transmit bacterial diseases to humans, and it appears that lower humoral and cellular immune responses allow body lice to possess a higher vector competence. We previously observed that the transcription level of the defensin 1 gene was up-regulated only in head lice following oral challenge of Bartonella quintana, a causative agent of trench fever, and also that body lice excreted more viable B. quintana in their feces. In this study, we first investigated this differential immune response by performing RNAi to knockdown defensin 1 by dsRNA injection. B. quintana was orally infected 72 h after injection and proliferation was compared at 2 hours (day 0) and day 4 post-infection. At day 0, bacterial cell numbers increased 1.5-fold in defensin 1 (Def1(-)) knocked down head lice compared with non-knocked down, pQE30-dsRNA injected, head lice control. At day 4, Def1(-) knocked down head lice had 2.55-fold more bacterial cells than control head lice and 1.65-fold greater than body lice, indicating that defensin 1 was active in reducing B. quintana cell number in non-knocked down head lice. Second, the levels of cytotoxic reactive oxygen species (ROS) generated by the epithelial cells of the alimentary tract were measured using two general indictors of ROS in both body and head lice at day 1 and day 4 following B. quintana challenge. Challenged body lice showed a 42% and 34% increase in ROS, whereas head lice showed a 70% and 22% increase at day 1 using CM-H2DCFDA and HPF as general indicators, respectively. On day 4, all challenged lice showed similar ROS levels except for body lice which maintained their ROS levels (40% increase using CM-H2DCFDA). Head lice are likely to have multiple immune and/or non-immune factors that suppress B. quintana proliferation, and the production of sustained ROS levels and/or the single knockdown of Defensin 1 is not enough to increase B. quintana proliferation in head lice to that seen in body lice.