帯広畜産大学博士（獣医学）Doctor of Veterinary Medicine2025application/pdfTick-borne haemopathogens (TBHPs) constitute a major threat to livestock health and productivity in Turkey, where the combination of diverse ecological landscapes and favorable climatic conditions supports the proliferation of tick populations and the transmission of multiple pathogens. Despite their importance, current knowledge regarding the molecular diversity and geographic distribution of TBHPs, particularly within tick vectors, remains limited and fragmented. Moreover, to date, no nationwide study has systematically investigated the prevalence of a broad spectrum of TBHPs in cattle, which represent the most economically important livestock species in the country. Bridging this knowledge gap is critical for the development of effective, evidence-based strategies for the surveillance, diagnosis, and control of tick-borne diseases in the country. Therefore, this doctoral dissertation presents a series of molecular epidemiological studies conducted across multiple regions of Turkey, aiming to enhance the understanding of TBHP circulation in both tick populations and their bovine hosts. In Chapter 1, a total of 1,281 adult ticks were collected from small ruminants across four districts in Konya Province, Turkey. The specimens were categorized into 357 pools according to tick species, sex, host animal, and collection site, and subsequently screened for haemoprotozoan infections using molecular assays. The infection rates were calculated by using a maximum likelihood estimate (MLE) with 95% confidence intervals (CI). The identified tick species included H. detritum, H. excavatum, Rh. bursa, Rh. sanguineus, and Rh.turanicus. Among the five tick species identified here, Rh. turanicus exhibited the highest infestation rate in both goats and sheep. The overall MLE of infection rates for B. ovis and T.ovis was 2.49% (CI 1.72–3.46) and 1.46% (CI 0.87–2.23), respectively. The MLE of B. ovis and T. ovis infection rates in Rh. bursa was 10.80% (CI 7.43–14.90) and 0.33% (CI 0.02–1.42), respectively, while that in Rh. turanicus was 0.12% (CI 0.01–0.51) and 2.08% (CI 1.25–3.22).This study further confirms that Rh. turanicus and Rh. sanguineus can act as vectors for B. ovis.In Chapter 2, a total of 277 adult ticks were collected from cattle in five provinces of Turkey and grouped into 90 DNA pools according to tick species, individual host, and sampling location. These pools were subjected to molecular screening for the presence of Babesia,Theileria, Anaplasma, Ehrlichia, Rickettsia, and Coxiella species. Four tick species were identified: H. excavatum, H. anatolicum, Rh. turanicus, and Rh. bursa. Among the detected pathogens, B. bovis was the most prevalent, with a minimum detection rate of 7.9%, followed by Ehrlichia spp. (7.2%), T. annulata (5.8%), Coxiella spp. (3.3%), A. marginale (2.5%),Rickettsia spp. (2.5%), and B. occultans (0.7%). The Rickettsia species identified included Candidatus Rickettsia barbariae, R. aeschlimannii, and Rickettsia sp. Chad. Notably, this study reports the first molecular detection of Rickettsia sp. Chad, a variant of Astrakhan fever Rickettsia, in Turkey. Moreover, H. excavatum was the only tick species in which all seven haemopathogens were detected. In Chapter 3, a total of 210 cattle blood samples collected from sixteen provinces in Turkey were examined using molecular methods. Of these, 133 cattle (63.3%) tested positive for at least one haemoprotozoan or haemobacterial pathogen. The overall prevalence rates were as follows: B. bovis (0.5%), B. bigemina (0.5%), B. occultans (1.4%), T. annulata (41.0%), T.orientalis (1.4%), A. marginale (10.5%), A. phagocytophilum (13.8%), A. bovis (0.5%),uncultured Anaplasma sp. (2.9%), E. minasensis (0.5%), uncultured Ehrlichia sp. (0.5%), and Mycoplasma sp. (23.3%). Single infections accounted for the majority of cases (63.9%), while double (24.8%), triple (7.5%), quadruple (2.3%), and quintuple (1.5%) co-infections were also observed. Notably, several pathogens rarely reported in Turkey, including B. occultans, T.orientalis, A. bovis, M. wenyonii, and Candidatus Mycoplasma haemobos, were identified.Sequencing and phylogenetic analyses further confirmed the first molecular detection of uncultured Ehrlichia sp. and E. minasensis in Turkish cattle, each showing 100% nucleotide identity with known sequences. T. annulata was the most frequently detected pathogen,underscoring its dominant role in bovine haemoparasitism.In conclusion, the three chapters of this dissertation provide a comprehensive characterization of the diversity and geographic distribution of TBHPs in both ticks and cattle across Turkey. The molecular evidence generated includes novel data from provinces where no previous information was available, thereby extending the known distributional range of these pathogens within the country. Moreover, the detection of zoonotic TBHPs in ticks feeding on cattle highlights the hidden public health dimension of tick-borne infections in the studied regions. The findings also confirm that cattle in Turkey are persistently exposed to a wide array of TBHPs, suggesting a substantial risk of subclinical and co-infections. These results highlight the urgent need to enhance national surveillance frameworks through the application of high-resolution molecular diagnostic tools. Furthermore, they support the adoption of integrated “One Health” strategies aimed at controlling and preventing TBDs that impact both animal and human populations. Collectively, the outcomes of this research offer critical baseline data to inform evidence-based policy and the implementation of targeted tick and TBD surveillance, prevention, and control programs within Turkey’s livestock sector.博士学位論文大学院畜産学研究科 獣医学専攻Doctoral Program of Veterinary Sciencedoctoral thesi
