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Prevalence and genetic diversity of Theileria and Anaplasma species infecting cattle in Paraguay
No full textBovine theileriosis and anaplasmosis are major tick-borne diseases affecting cattle health and productivity worldwide. Although cattle farming significantly contributes to Paraguay's economy, limited epidemiological data on the causative agents hinder the formulation of disease control measures. To address this challenge, the present study investigated the prevalence, risk factors, and genetic diversity of Theileria annulata, Theileria orientalis, and Anaplasma marginale among cattle populations in Paraguay. Blood DNA samples from 326 cattle in nine departments of Paraguay were screened with the pathogen-specific PCR assays. All three pathogens were detected with A. marginale (18.0 %) being the most prevalent, followed by T. orientalis (2.4 %) and T. annulata (1.5 %). In addition, further screening of A. marginale-negative samples using two PCR assays targeting the 16S rRNA and groEL genes of Anaplasma spp., followed by sequencing, detected an infection with Candidatus Anaplasma cinensis. We observed significantly higher A. marginale-positive rates in the Eastern region, males, and extensively managed cattle, as compared to those in the Western region, females, and semi-intensively managed cattle, respectively. Phylogenetic analyses revealed that T. annulata tams1 gene sequences were diverse and occurred in multiple clades, while T. orientalis mpsp gene sequences clustered into the genotypes 1, 2, and 3. In contrast, A. marginale msp5 gene sequences occurred within a single clade, suggesting a low genetic diversity. In conclusion, the detection of T. annulata, T. orientalis genotype 2, and A. marginale indicates that cattle populations in Paraguay are at risk of clinical theileriosis and anaplasmosis, highlighting the need to develop disease management strategies. © 2025 Elsevier B.V
An epidemiological survey of equine piroplasmosis in donkeys and horses in Malawi
No full textEquine piroplasmosis (EP) is a tick-borne disease caused by Theileria equi, Theileria haneyi, and Babesia caballi in equids, such as horses, donkeys, mules, and zebras. A comprehensive understanding of the epidemiology of T. equi and B. caballi is vital for EP management. The present study surveyed T. equi and B. caballi infections in donkeys and horses in Malawi. Blood samples were collected from 185 equines, including 178 donkeys in Lilongwe (n = 136) and Dedza (n = 42) districts, and seven horses in Lilongwe district. The blood samples were used to measure hematocrit values and prepare thin smears and blood spots on FTA cards. Microscopic examination of the blood smears detected T. equi in 91 equines (49.2 %), including 88 donkeys (49.4 %) and three horses (42.9 %), while B. caballi was not detected. Screening of DNA samples extracted from FTA cards with species-specific PCR assays detected T. equi in 156 (84.3 %) equines, including 152 (85.4 %) donkeys and four (57.1 %) horses, whereas all animals were negative for B. caballi. We found that the mean hematocrit value of infected donkeys (28.1 %) was significantly lower (P value = 0.0004) than that of uninfected donkeys (31.9 %). Additional analysis of T. equi-positive DNAs with the genotype-specific PCR assays detected all five genotypes (A, B, C, D, and E) in donkeys and four genotypes (A, B, C, and D) in horses. In summary, the present study, the first to report the T. equi infection in Malawi, suggests the need for EP control due to its potential clinical significance. © 2025 Elsevier B.V
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Behavioral and socio-economic study on BMP adoption and antibiotic use avoidance in shrimp aquaculture in Sri Lanka
Get PDF帯広畜産大学博士（農学）Doctor of Agriculture2025application/pdfThe rapid growth of shrimp farming in many developing countries, including Sri Lanka, has raised serious concerns about environmental sustainability, public health, and regulatory compliance. The frequent occurrence of disease and the resulting economic losses suggest that farmers may be using antibiotics that are prohibited. Such practices not only undermine long-term sustainability but also pose serious risks to food safety, with the issue of antimicro-bial resistance (AMR) gaining increasing attention in recent years.
To mitigate these risks, Best Management Practices (BMPs) are being increasingly adopted worldwide. In Sri Lanka, organizations such as the National Aquaculture Development Au-thority (NAQDA) and the Sri Lanka Aquaculture Development Association (SLADA) are promoting the adoption of BMPs. Under BMPs, the use of any type of antibiotic is prohibited. In tropical aquaculture, disease management remains a major challenge, particularly regard-ing compliance with existing regulations and guidelines among aquaculture farmers.
In such circumstances, it is important to understand the influence of farmers' knowledge, atti-tudes, and practices (KAP), as well as behavioural biases such as resistance to change and risk aversion. These factors impact farmers' decision-making regarding compliance with BMPs and the potential use of antibiotics. The main objective of this paper is to elucidate the behav-ioural factors behind the adoption of BMPs and the avoidance of antibiotic use in sustainable shrimp farming in Sri Lanka, and to propose evidence-based sustainable fisheries policies. This study consists of the following three research findings (Chapters 3, 4, and 5) conducted in Putthalam District, the production center of shrimp farming in Sri Lanka.
Chapter 3 scientifically evaluated shrimp farmers' knowledge and adoption levels of BMPs and identified behavioural determinants related to BMP adoption. Data were collected from 131 farmers using a questionnaire. According to the analysis results, 37% of respondents had a high level of knowledge about BMPs, while another 37% had a moderate level of knowledge. However, the adoption status of BMPs varied, with only 9% reporting a high lev-el of adoption. The results of the ordinal logistic regression (with BMP knowledge and adop-tion levels as the dependent variables) showed that experience in BMP training, educational level, and labour force size significantly influenced BMP knowledge, while age, farming ex-perience, the proportion of income from shrimp, and risk preference significantly influenced BMP adoption. The analysis results indicate that while expanding BMP training is beneficial, it must be implemented with consideration for the underlying social factors.
Chapter 4 focuses on antibiotic residues in shrimp and examines the socioeconomic and be-havioural factors involved. Shrimp samples were randomly collected from 91 aquaculture farms in the Puttalam district, and residue tests for oxytetracycline (OTC), erythromycin (ERY), and chloramphenicol (CAP) were conducted using the ELISA method. The results showed that 77% of the samples contained OTC residues, 62% contained CAP residues, and 48% contained ERY residues. Probit regression analysis and Tobit regression analysis re-vealed a significant reduction in OTC residues among farmers who participated in BMP train-ing. ERY residues were positively correlated with the income ratio and risk preference of shrimp farmers. These results revealed the existence of a principal-agent problem, in which the behaviour of farmers (agents) with economic incentives and disease risks is inconsistent with the health and safety goals set by regulatory authorities (principals).
In Chapter 5, we evaluated the effectiveness of existing training programs and peer learning videos, in which farmers learn from each other, with the aim of improving knowledge and adoption of BMPs. Ninety aquaculture farmers were divided into three groups: a control group (no intervention), an existing training group, and a peer learning group. Behavioral changes three months after the intervention were confirmed through questionnaires. Both in-tervention groups showed statistically significant improvements in BMP knowledge com-pared to the control group. Peer learning videos were particularly effective in raising aware-ness of the need to avoid antibiotic use.
BMP compliance items were categorized into “pond hygiene management,” “shrimp health management,” and “input management” for analysis. The results showed that peer learning videos and farmer characteristics (education, age, etc.) had a significant impact on BMP adoption scores. These findings indicate that peer learning videos, which are currently not implemented in Sri Lanka, can enhance BMP knowledge and compliance levels and effective-ly promote antibiotic avoidance behaviour.
This paper revealed that there is a gap between knowledge and adoption of BMPs in shrimp farming in Sri Lanka due to socioeconomic, behavioural, and institutional challenges. The detection of antibiotic residues indicates the need for stricter monitoring of antibiotic regula-tions and BMP compliance. While improvements in knowledge are evident, there is a need to address financial and behavioural barriers to long-term change.
This study found that behavioural economics and principal-agent theory are effective in im-plementing sustainable fisheries policies and provided new insights into the existing body of research on aquaculture.
An integrated approach incorporating the One Health perspective, antibiotic avoidance, and BMP implementation is important from the perspectives of environmental sustainability, im-proved shrimp farming productivity, public health, and long-term food safety in Sri Lanka.博士学位論文大学院畜産学研究科 畜産科学専攻Doctoral Program of Animal Science and Agriculturedoctoral thesi
Molecular epidemiological investigation of tick-borne haemopathogens in ticks and livestock in Turkey
Get PDF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
Evaluation of long-term roadkill monitoring as a population index : Case study of raccoon dogs (Nyctereutes procyonoides)
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国内ホルスタイン種の暑熱ストレス耐性改良のための代謝関連形質データ応用に関する研究
Get PDF帯広畜産大学博士（農学）Doctor of Agriculture2024application/pdf博士学位論文大学院畜産学研究科 畜産科学専攻Doctoral Program of Animal Science and Agriculturedoctoral thesi