Application of PCR to a clinical and environmental investigation of a case of equine botulism

PCR for the detection of botulinum neurotoxin gene types A to E was used in the investigation of a case of equine botulism. Samples from a foal diagnosed with toxicoinfectious botulism in 1985 were reanalyzed by PCR and the mouse bioassay in conjunction with an environmental survey. Neurotoxin B was detected by mouse bioassay in culture enrichments of serum, spleen, feces, and intestinal contents. PCR results compared well with mouse bioassay results, detecting type B neurotoxin genes in these samples and also in a liver sample. Other neurotoxin types were not detected by either test. Clostridium botulinum type B was shown to be prevalent in soils collected from the area in which the foal was raised. Four methods were used to test for the presence of botulinum neurotoxin-producing organisms in 66 soil samples taken within a 5-km radius: PCR and agarose gel electrophoresis (types A to E), PCR and an enzyme-linked assay (type B), hybridization of crude alkaline cell lysates with a type B-specific probe, and the mouse bioassay (all types). Fewer soil samples were positive for C. botulinum type B by the mouse bioassay (15%) than by any of the DNA-based detection systems. Hybridization of a type B-specific probe to DNA dot blots (26% of the samples were positive) and PCR-enzyme-linked assay (77% of the samples were positive) were used for the rapid analysis of large numbers of samples, with sensitivity limits of 3 x 10(6) and 3,000 cells, respectively. Conventional detection of PCR products by gel electrophoresis was the most sensitive method (300-cell limit), and in the present environmental survey, neurotoxin B genes only were detected in 94% of the samples

Studies on equine herpesviruses - II. Development of a complement fixation test antigen of cell culture origin for equine Herpes-1 (Rhinopneumonitis) virus and use in a microtitre system

A complement fixation (CF) antigen for equine herpes-1 (rhinopneumonitis) virus (EHV 1) of cell culture origin was studied, and an optimum method of preparation in a minimum volume of serum-free overlay fluid developed. Many chemical and physical treatments including fluorocarbon extraction, tweenether treatment, Carbowax concentration or ultracentrifugation (25,000 g) did not further improve the quality of this antigen. Inactivation (56°C for 30 minutes) of equine serum did not affect the CF antibody titre, but removed low levels of anti-complementary activity. The use of a diluent of low ionic strength (0.1 m) did not increase titres in the EHV 1-equine antibody CF system. This EHV 1 CF antigen of cell culture origin was used in a microtitre system and detected the development of antibodies in all of six young horses in Queensland following natural EHV 1 respiratory infection. Maximum serum titres (1/128) were reached 1-2 weeks after the onset of acute respiratory disease, then CF titres declined steadily but were still detectable after 12 months. Serum titres of 1/16-1/32 or higher indicated EHV 1 infection to have occurred within the previous 3-6 months

Cognitive Learning Styles and Digital Equity: Searching for the Middle Way

This research is driven by a desire to understand the lifelong learner in the context of styles of learning and the emerging implications of technology enhanced learning for digital equity. Recognizing cognitive learning styles is the first step educators need to take in order to be most effective in working with students of diversity and bridging across formal and informal settings. Learning environments as a characterising feature of learning styles have undergone unprecedented change over the past decade with learning environments now blending physical and virtual space. To support the increasing diversity of learners pedagogy has to be fair, culturally responsive, equitable and relevant to the ‘virtual generation’. This in turn will inform our understanding of the ‘middle way’ in recognising cognitive learning styles , associated cultural context, and the implications to digital pedagogy equity