Cloning and expression of Rift Valley fever virus nucleocapsid (N) protein and evaluation of a N-protein based indirect ELISA for the detection of specific IgG and IgM antibodies in domestic ruminants

Serodiagnosis of Rift Valley fever (RVF) currently relies on the use of live or inactivated whole virus as antigens. The recombinant nucleocapsid (N) protein of RVF virus was tested for diagnostic applicability in an indirect enzyme-linked immunosorbent assay (I-ELISA), using sera from experimentally infected sheep (n=128), vaccinated sheep (n=240), and field-collected sera from sheep (n=251), goats (n=362) and cattle (n=100). The N-protein based I-ELISA performed at least as good as VN and HI tests. In goat the diagnostic sensitivity (D-Sn) and specificity (D-Sp) of the I-ELISA was 100% when using the anti-species IgG conjugate. Using protein G as a detection system, the D-Sn and D-Sp in goats were 99.4% and 99.5%, in sheep field sera both 100%, in cattle 100% and 98.3%, respectively. The I-ELISA based on recombinant N-protein has the potential to complement the traditional assays for serodiagnosis of RVF. Advantages of the N-protein are its safety, stability and cost-effectiveness in use and production.     

Agreement between computed tomography, magnetic resonance imaging, and surgical findings in dogs with degenerative lumbosacral stenosis

OBJECTIVE: To assess the extent of agreement between computed tomography (CT), magnetic resonance imaging (MRI), and surgical findings in dogs with degenerative lumbosacral stenosis. DESIGN: Observational study. ANIMALS: 35 dogs with degenerative lumbosacral stenosis. PROCEDURES: Results of preoperative CT and MRI were compared with surgical findings with respect to degree and location of disk protrusion, position of the dural sac, amount of epidural fat, and swelling of spinal nerve roots. RESULTS: A lumbosacral step was seen on radiographic images from 22 of 32 (69%) dogs, on CT images from 23 of 35 (66%) dogs, and on MR images from 21 of 35 (60%) dogs. Most dogs had slight or moderate disk protrusion that was centrally located. There was substantial or near perfect agreement between CT and MRI findings in regard to degree of disk protrusion (kappa, 0.88), location of disk protrusion (0.63), position of the dural sac (0.89), amount of epidural fat (0.72), and swelling of spinal nerve roots (0.60). The degree of agreement between CT and surgical findings and between MRI and surgical findings was moderate in regard to degree and location of disk protrusion (kappa, 0.44 to 0.56) and swelling of spinal nerve roots (0.40 and 0.50). CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that there is a high degree of agreement between CT and MRI findings in dogs with degenerative lumbosacral stenosis but that the degree of agreement between diagnostic imaging findings and surgical findings is lower.     

Model for Simulation of Particle Flow on a Centrifugal Fertiliser Spreader

An analysis of the motion of a particle on a rotating flat disc is conducted and a basic equation of motion derived for a single particle. The analysis is directly applied to the flow of particles on a centrifugal fertiliser spreader. Equations of motion are derived for flat disc/radial vanes type of spreaders and further generalised for the more common conical disc/pitched vanes type. The derived equations of motion form part of the basis of a simulation model for centrifugal (or spinning disc) fertiliser spreaders with the equations of motion through the air completing the model. In the simulation, the collective flow of particles is treated as a superposition of single-particle trajectories with different initial conditions. The spreader model is applicable for the development of spreader control systems for site-specific fertiliser application as well as for the design and optimisation of spreaders.     

Comparison of linear and nonlinear regression for modeling the first-order degradation of pest-control substances in soil

First-order kinetic models are often used to profile the degradation of pest-control compounds in soil. This approach is based on enzyme theory and is often favored due to its simplicity and its requirement by regulatory agencies. Here, linear and nonlinear regression approaches to modeling first-order decay are compared. Composite residual plots of many soil degradation data sets are presented on a normalized scale. These plots illustrate the general error structure for the data and are useful for detecting common mis-specifications of the models. Results indicate that a nonlinear regression approach to modeling first-order decay of compounds in soil more accurately describes most data sets when compared with a linear approach. Specifically, the observed error structure does not support the broad use of a logarithmic transformation to stabilize the variance. In addition, models generated using the linear approach generally exhibit more dramatic systematic deviations from the observations as compared with models generated using the nonlinear approach. The analysis methods described here may be useful for comparing alternative models in this and other research areas.     

Diffuse idiopathic skeletal hyperostosis (DISH) and spondylosis deformans in purebred dogs: a retrospective radiographic study

A retrospective radiographic study was performed to investigate the prevalence of diffuse idiopathic skeletal hyperostosis (DISH) and spondylosis deformans (spondylosis) in 2041 purebred dogs and to determine association with age, gender and breed. Four cases of DISH provided information on the appearance of canine DISH. The prevalence of DISH and spondylosis was 3.8% (78/2041) and 18.0% (367/2041), respectively. Of dogs with DISH, 67.9% (53/78) also had spondylosis, whereas 14.0% (53/367) of dogs with spondylosis also had DISH. Dogs with DISH and/or spondylosis were significantly older than those without spinal exostosis. The prevalence of DISH and spondylosis was 40.6% (28/69) and 55.1% (38/69), respectively, in Boxer dogs. Nineteen smaller breeds were not affected by DISH, but showed signs of spondylosis; only standard Poodles appeared not to be affected by either disorder. Radiography, computed tomography (CT), magnetic resonance imaging (MRI), and/or histopathology were used to investigate four DISH cases. It was concluded that spondylosis and DISH can co-occur in dogs. DISH has probably been previously under-diagnosed and mistaken for severe spondylosis. The diagnosis can be made using radiography, CT or MRI. On histology, DISH can be distinguished from spondylosis by the location (ventral longitudinal ligament) and extent of new bone formation.     

Life history data of the rosy apple aphid<Emphasis Type="Italic"> Dysaphis plantaginea</Emphasis> (Pass.) (Homopt., Aphididae) on plantain and as migrant to apple

The rosy apple aphid Dysaphis plantaginea (Passerini) is a key pest in western European apple orchards; the economic damage threshold is so low that outbreaks cannot be forecasted. A mass rearing of the species on plantain (Plantago lanceolata L.) was initiated, with the aim to infest apple trees with either the autumn migrants, gynoparae and males, or the egg-laying females (oviparae). Here, data are presented about the propagation of the species on plantain, on the production of autumn migrants under laboratory conditions, and on the duration of juvenile development and reproductive capacities of both gynoparae and oviparae. Under long-day conditions (18 h light/day) on plantain, the thermal constant for the duration of juvenile development was 166 dd (day-degrees) above the lower development threshold of 5.1 °C, and daily larviposition amounted to 1.87 times the temperature (°C)minus 0.8, above a lower threshold of 4.3 °C. Between 32 and 36 larvae were produced by the young female before the first larvae become adult and their reproduction started to overshadow their mothers. A plant freshly infested with 12 reproducing females and transferred to short-day conditions (12 h light/day) yielded up to 5,000 autumn migrants, with males in the majority. The first gynoparae appeared after about 25 days at both 16 and 20 °C, and males appeared after 40 and 33 days, respectively. Young adult gynoparae produced most of their about ten offspring right after landing on apples, unless temperature was well below 15 °C. The duration of juvenile development of these oviparae appeared to be rather variable and their egg-laying so protracted that each of these females needs to survive several weeks to produce a handful of winter eggs. With reproductive capacities of up to 14 progeny/female for gynoparae and 7.4 for oviparae, release of one gynopara in the field could theoretically lead to the deposition of 100 winter eggs.