Evaluation of three serum i-ELISA's using monoclonal antibodies and protein G as peroxidase conjugate for the diagnosis of bovine brucellosis

Three i-ELISAs using LPS, the immunodominant component of Brucella abortus, were developed with three different conjugates: monoclonal antibodies 1C8 (anti-bovine IgG(1)) and 3H3 (mainly specific for bovine IgG(2) but also reacting with IgG(1)) and protein G (reacts with both bovine IgG subclasses). Using a cut-off value of 2.5U/ml, the i-ELISA with 3H3 as conjugate had a specificity (95% CI: 98.32-99.63%) that was significantly higher than the same assay with 1C8 (95% CI: 96.08-98.26%) or PG (95% CI: 95.83-98.09%). In areas where false positive serological reactions (FPSR) were common, the specificity of the i-ELISAs decreased significantly. The specificity of the i-ELISAs increased with the age of the animals tested, irrespective of the conjugate. The specificity of the i-ELISAs and traditional tests was also examined using sera from animals infected per os with bacteria bearing LPS similar to the Brucella LPS. It appeared that Yersinia enterocolitica O:9, Xanthomonas maltophilia and Salmonella urbana infections induced FPSR both in the i-ELISAs and in the traditional tests, but the 3H3 assay was significantly less prone to produce false positive reactions than the 1C8 and PG assays. The i-ELISAs were more sensitive, allowed earlier detection, and were more persistent than the traditional serological tests both in experimentally and naturally Brucella-infected animals. Weekly i-ELISA monitoring of experimentally infected pregnant heifers (previously vaccinated or not) allowed a prediction of abortion. Furthermore, the 1C8 assay showed significantly higher titres irrespective of day post-infection and vaccination status. The accuracy of the assay could be improved by making use of additional information (e.g. animal age or conjugate) and by selecting appropriate cut-off points on the basis of the prevailing epidemiological situation. The i-ELISAs appear an appropriate choice in order to maintain an official brucellosis-free status because of their sensitivity, early detection and long persistence and, for the same reasons, seem especially valuable for the detection of latent carriers (i.e. animals classified negative by classical serological tests) among importe

Human Brucellosis in Northwest Ecuador: Typifying Brucella spp., Seroprevalence, and Associated Risk Factors

Human brucellosis in Ecuador is underreported and based only on passive surveillance. Since 2008, brucellosis was removed from the list of communicable diseases in the country. Until now, the true human brucellosis picture has not yet been determined. The aim of this study was to determine the seroprevalence of the disease, identify risk factors associated with brucellosis seropositivity in humans, and isolate circulating strains of Brucella spp. in the northwestern part of Ecuador. Between 2006 and 2008, a large transect survey was conducted, based on blood sampling of people from the northwestern part of Ecuador (n=3733) together with an epidemiological inquiry. On the basis of three diagnostic tests used in parallel, the overall seroprevalence was estimated as 1.88% (95% confidence interval [CI] 1.48-2.38). Based on a multivariable random effects logistic regression analysis, the main risk factors associated with human brucellosis seropositivity were contact with livestock (odds ratio [OR]=3.0; CI 1.25-7.08), consumption of fetus and placenta (OR=2.5; CI 1.18-5.22), and involvement in activities at risk for brucellosis infection (OR=1.8; CI 1.00-3.35). Noticeable variation in brucellosis seropositivity among humans within cantons was observed. The circulating strain was Brucella abortus biotype 4. This study emphasized that contact with livestock, consumption of fetus and placenta, and occupational hazard group were all significant risk factors for the transmission of brucellosis among individuals in the northwestern part of Ecuador. Alongside encouraging the launching of educational campaigns against brucellosis, especially in rural areas where 36% of the population lives, controlling this zoonotic disease in animals will directly benefit its prevention in humans, especially because there is no safe and efficacious vaccine against brucellosis in humans

Advantages of concurrent use of multiple software frameworks in water quality modelling using a database approach

Water quality modelling deals with multidisciplinary questions ranging from fundamental to applied. Addressing this broad range of questions requires multiple analysis techniques and therefore multiple frameworks. Through the recently developed database approach to modelling (DATM), it has become possible to run a model in multiple software frameworks without much overhead. Here we apply DATM to the ecosystem model for ditches. PCDitch and its twin model for shallow lakes PCLake. Using DATM, we run these models in six frameworks (ACSL, DELWAQ, DUFLOW, GRIND for MATLAB, OSIRIS and R), and report on the possible model analyses with tools provided by each framework. We conclude that the dynamic link between frameworks and models resulting from DATM has the following main advantages: it allows one to use the framework one is familiar with for most model analyses and eases switching between frameworks for complementary model analyses, including the switch between a 0-D and 1-D to 3-D setting. Moreover, the strength of each framework – including runtime performance – can now be easily exploited. We envision that a community-based further development of the concept can contribute to the future development of water quality modelling, not only by addressing multidisciplinary questions but also by facilitating the exchange of models and process formulations within the community of water quality modellers

Serving many at once: How a database approach can create unity in dynamical ecosystem modelling

Simulation modelling in ecology is a field that is becoming increasingly compartmentalized. Here we propose a Database Approach To Modelling (DATM) to create unity in dynamical ecosystem modelling with differential equations. In this approach the storage of ecological knowledge is independent of the language and platform in which the model will be run. To create an instance of the model, the information in the database is translated and augmented with the language and platform specifics. This process is automated so that a new instance can be created each time the database is updated. We describe the approach using the simple Lotka–Volterra model and the complex ecosystem model for shallow lakes PCLake, which we automatically implement in the frameworks OSIRIS, GRIND for MATLAB, ACSL, R, DUFLOW and DELWAQ. A clear advantage of working in a database is the overview it provides. The simplicity of the approach only adds to its elegance.

Serving many at once: How a database approach can create unity in dynamical ecosystem modelling

Simulation modelling in ecology is a field that is becoming increasingly compartmentalized. Here we propose a Database Approach To Modelling (DATM) to create unity in dynamical ecosystem modelling with differential equations. In this approach the storage of ecological knowledge is independent of the language and platform in which the model will be run. To create an instance of the model, the information in the database is translated and augmented with the language and platform specifics. This process is automated so that a new instance can be created each time the database is updated. We describe the approach using the simple LotkaeVolterra model and the complex ecosystem model for shallow lakes PCLake, which we automatically implement in the frameworks OSIRIS, GRIND for MATLAB, ACSL, R, DUFLOW and DELWAQ. A clear advantage of working in a database is the overview it provides. The simplicity of the approach only adds to its elegance