Direct correlation between potentiometric and impedance biosensing of antibody-antigen interactions using an integrated system

A fully integrated system that combines extended gate field-effect transistor (EGFET)-based potentiometric biosensors and electrochemical impedance spectroscopy (EIS)-based biosensors has been demonstrated. This integrated configuration enables the sequential measurement of the same immunological binding event on the same sensing surface and consequently sheds light on the fundamental origins of sensing signals produced by FET and EIS biosensors, as well as the correlation between the two. Detection of both the bovine serum albumin (BSA)/anti-BSA model system in buffer solution and bovine parainfluenza antibodies in complex blood plasma samples was demonstrated using the integrated biosensors. Comparison of the EGFET and EIS sensor responses reveals similar dynamic ranges, while equivalent circuit modeling of the EIS response shows that the commonly reported total impedance change (DZtotal) is dominated by the change in charge transfer resistance (Rct) rather than surface capacitance (Csurface). Using electrochemical kinetics and the Butler-Volmer equation, we unveil that the surface potential and charge transfer resistance, measured by potentiometric and impedance biosensors, respectively, are, in fact, intrinsically linked. This observation suggests that there is no significant gain in using the FET/EIS integrated system and leads to the demonstration that low-cost EGFET biosensors are sufficient as a detection tool to resolve the charge information of biomolecules for practical sensing applications

Liver fluke in Irish sheep: prevalence and associations with management practices and co-infection with rumen fluke

peer-reviewedBackground: The present study aimed to identify the national prevalence of Fasciola hepatica in Irish sheep and to conduct a risk analysis assessment based on management and treatment practices in participating focks. Also, co-infection with rumen fuke was quantifed and its association with liver fuke and management practices was assessed. Methods: A total of 305 sheep focks were selected ensuring even national representation of the sheep population. Participating farms were asked to complete a survey questionnaire on farm management practices and submit faecal samples during the winter of 2014–2015. Pooled faecal samples were analysed for the presence of F. hepatica and coinfection with rumen fuke. Apparent and true prevalence were calculated, additionally, the rate of co-infection with rumen fuke was also obtained. Correlation and regression analyses were used for assessing associations between management practices, liver fuke infection and co-infection with rumen fuke. Results: The national true prevalence of F. hepatica was 50.4% (n=305). Regional prevalence varied from 41% in the east to 52% in the south. Co-infection with rumen fuke was observed in 40% of the studied population and corre‑ lated with increased F. hepatica egg counts (OR=2.9; P≤0.001). Predominant breeds were Sufolk, Texel and Horned Mountain breeds. Beef cattle were the most frequent type of other livestock present on farms and mixed species grazing was frequently reported (73%). More than half of the focks reported a mid-to-late lambing period (MarchApril). Use of mountain land for grazing was of 32%. Flukicides were most commonly used twice over the autumnwinter period. Regression analyses highlighted signifcant association of F. hepatica status, with the presence of other livestock on farm, frequency of fukicides used during the winter and clinical presentation of liver fuke. A signifcant increase in eggs per gram of faeces was observed in Charollais sheep in comparison with all other breeds. Co-infec‑ tion with F. hepatica and Calicophoron daubneyi was also signifcantly associated with the presence of other livestock on the farm, type of fukicide used and clinical fasciolosis. Conclusions: The present study provides up-to-date information on the prevalence of F. hepatica in Irish sheep and adds insight to the epidemiology of the disease. These fndings will be useful for designing new holistic control meas‑ ures for F. hepatica infection

Biosecurity, bovine viral diarrhoea virus (BVDv), and bovine herpesvirus-1 (BoHV-1): epidemiological investigations in Irish dairy herds

The fundamental basis of herd health planning and disease control is a science-based risk analysis. A disease risk analysis involves examining the probability of a disease occurring and the impact of that disease should it occur. Epidemiological investigations are required to provide the necessary data on biosecurity, disease prevalence, vaccination, and production losses associated with a particular infectious agent for the purposes of a comprehensive risk analysis. BVDv and BoHV-1 are highly contagious cattle viruses, exhibit a worldwide distribution and are listed as notifiable diseases by the OIE (Office International des Epizooties). A national eradication scheme is currently underway in Ireland for BVDv but no co-ordinated programme exists for the control or eradication of BoHV-1. Relatively little published data are available on the prevalence or production losses associated with BVDv and BoHV-1 infection in Ireland. Neither are data available relating to current biosecurity and vaccination practices on Irish dairy farms. The research programme outlined in this thesis aimed to provide relevant Irish stakeholders, such as AHI (Animal Health Ireland) and DAFM (Department of Agriculture, Food and the Marine), the necessary data to conduct an informed risk analysis on BVDv and BoHV-1. Results show that biosecurity practices, in general, were poorly implemented on dairy farms with lack of information cited as the primary cause. The concept of biosecurity was not well understood, a 20% discrepancy highlighted between self-declared and truly ‘closed’ herds. Additionally, inconsistencies in biosecurity practices and opinions across veterinarians, dairy advisors, and farmers were highlighted emphasising the need for improved communication amongst these stakeholders. Poor implementation of biosecurity is reflected in the prevalence of exposure to BVDv and BoHV-1 recorded in the current study. From a geographically representative population of 312 dairy herds, an apparent prevalence of 88% and 80% was recorded for BVDv and BoHV-1, respectively. Additionally, approximately one third of participating herds were spot test (youngstock screen used to indicate recent viral circulation) positive for BVDv antibodies indicating extensive BVDv circulation in 2009. Over 60% of study herds vaccinated against BVDv and 12% against BoHV-1. Such extensive use of BVDv vaccine necessitated examination of the impact of vaccine administration on BVDv bulk milk testing as bulk milk analysis is likely to be an important tool in on-going national BVD surveillance. One commercially available inactivated BVD vaccine was shown not to interfere with BVD p80 bulk milk antibody interpretation making it a useful tool in BVD control during eradication. BVDv and BoHV-1 antibody positive herds were found to record inferior production performance than antibody negative herds. Herds with evidence of recent BVDv circulation and herds bulk milk antibody positive for BoHV-1 recorded the most significant production losses. These losses will act as important motivators in engaging farmers in national eradication and control programmes for both BVDv and BoHV-1. The baseline data documented in this thesis will form the basis for more detailed sociological, economic, and epidemiological research to facilitate targeting of future training of, and risk communication with, the dairy farming community in Ireland

Focus on recognition Trade union trends survey 00/1 on union recognition

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