Local spread of classical swine fever upon virus introduction into The Netherlands: Mapping of areas at high risk

Background

In the recent past, the introduction of Classical Swine Fever Virus (CSFV) followed by between-herd spread has given rise to a number of large epidemics in The Netherlands and Belgium. Both these countries are pork-exporting countries. Particularly important in these epidemics has been the occurrence of substantial "neighborhood transmission" from herd to herd in the presence of base-line control measures prescribed by EU legislation. Here we propose a calculation procedure to map out "high-risk areas" for local between-herd spread of CSFV as a tool to support decision making on prevention and control of CSFV outbreaks. In this procedure the identification of such areas is based on an estimated inter-herd distance dependent probability of neighborhood transmission or "local transmission". Using this distance-dependent probability, we derive a threshold value for the local density of herds. In areas with local herd density above threshold, local transmission alone can already lead to epidemic spread, whereas in below-threshold areas this is not the case. The first type of area is termed 'high-risk' for spread of CSFV, while the latter type is termed 'low-risk'.

Results

As we show for the case of The Netherlands, once the distance-dependent probability of local transmission has been estimated from CSFV outbreak data, it is possible to produce a map of the country in which areas of high-risk herds and of low-risk herds are identified. We made these maps even more informative by estimating border zones between the two types of areas. In these border zones the risk of local transmission of infection to a nearby high-risk area exceeds a certain level.

Conclusion

The risk maps provide an easily understandable visualization of the spatial heterogeneities in transmission risk. They serve as a tool for area-specific designs of control strategies, and possibly also for spatial planning of areas where livestock farming is allowed. Similar risk maps can in principle be constructed for other highly-transmissible livestock infections that spread via neighborhood transmission.

     

Effects of fixation on routine,special and immunohistochemical stains: introduction to a symposium for the Biological Stain Commission

Orcein was first proposed as an elastic fiber stain by Taenzer in 1890, and has proved very useful for the purpose. It is an important constituent of the author's “Quad” stain. Unfortunately not all orcein samples have proved equally satisfactory, whether they are derived from the lichens from which the dye was originally prepared or have been manufactured by a synthetic process. At the present time several brands are available, and two of the brands of the synthetic product investigated have not proved to be the same thing; one of the latter proves only fair as an elastin stain, the other is one of the best samples the author has ever tried.     

Self-consistent band theoretic models of DNA

Previously investigated models are further elaborated here, with particular application to DNA. Accepting the premise that DNA may be characterized as an intrinsic semiconductor with a band gap energy of approximately 2 eV, a self-consistent method reveals term energies of reasonable magnitude. The treatment also determines that the mobilities are of the order of 10 to 10² cm²/V sec, indicating delocalization of the electrons with respect to the base pairs.     

Modulation of the Acetylcholine System in the Superior Cervical Ganglion of Rat: Effects of GABA and Hypoglossal Nerve Implantation After In Vivo GABA Treatment

gamma-Aminobutyric acid (GABA) was applied to the superior cervical ganglion (SCG) of CFY rats in vitro and in vivo, with or without implantation of a hypoglossal nerve, to evaluate the effects of these experimental interventions on the acetylcholine (ACh) system, which mainly serves the synaptic transmission of the preganglionic input. Long-lasting GABA microinfusion into the SCG in vivo apparently resulted in a "functional denervation." This treatment reduced the acetylcholinesterase (AChE; EC 3.1.1.7) activity by 30% (p less than 0.01) and transiently increased the number of nicotinic acetylcholine receptors, but had no significant effect on the choline acetyltransferase (acetyl-coenzyme A:choline-O-acetyltransferase; EC 2.3.1.6) activity, the ACh level, or the number of muscarinic acetylcholine receptors. The relative amounts of the different molecular forms of AChE did not change under these conditions. In vivo GABA application to the SCG with a hypoglossal nerve implanted in the presence of intact preganglionic afferent synapses exerted a significant modulatory effect on the AChE activity and its molecular forms. The "hyperinnervation" of the ganglia led to increases in the AChE activity (to 142.5%, p less than 0.01) and the 16S molecular form (to 200%, p less than 0.01). It is concluded that in vivo GABA microinfusion and GABA treatment in the presence of additional cholinergic synapses has a modulatory effect on the elements of the ACh system in the SCG of CFY rats.     

A cross-sectional study to determine the seroprevalence of bluetongue virus serotype 8 in sheep and goats in 2006 and 2007 in the Netherlands

Background

In August 2006 a major epidemic of bluetongue virus serotype 8 (BTV8) started off in North-West Europe. In the course of 2007 it became evident that BTV8 had survived the winter in North-West Europe, re-emerged and spread exponentially. Recently, the European Union decided to start vaccination against BTV8. In order to improve the understanding of the epidemiological situation, it was necessary to execute a cross-sectional serological study at the end of the BT vector season. Cattle were the target species for cross-sectional serological studies in Europe at the end of 2006 and 2007. However, there was no information on the BTV8-seroprevalence in sheep and goats.

Results

On the basis of our cross-sectional study, the estimated seroprevalence of BTV8-exposed locations in the Netherlands in 2006 was 0% for goats (95% confidence interval: 0 – 5.6%) and 7.0% for sheep (95% confidence interval: 3.5 – 12.9%). The estimated seroprevalence of BTV-8 exposed locations in 2007 was 47% for goats (95% confidence interval: 36 – 58%) and 70% for sheep (95% confidence interval: 63 – 76%). There was a wide range in within-location seroprevalence in locations with goats and sheep (1 – 100%). A gradient in seroprevalence was seen, with the highest level of seroprevalence in the southern Netherlands, the area where the epidemic started in 2006, and a decreasing seroprevalence when going in a northern direction.

Conclusion

There is a much higher estimated seroprevalence of locations with goats exposed to BTV8 than can be inferred from the rather low number of reported clinical outbreaks in goats. This is probably due to the fact that clinical signs in infected goats are far less obvious than in sheep. The wide range in within-location seroprevalence observed means that the proportion of animals protected in 2008 by a natural infection in 2006 and/or 2007 can differ highly between flocks. This should be taken into account when vaccinating animals.

     

Northwest passages: conservation genetics of Arctic Island wolves

Wolves in the Canadian Arctic Archipelago face several challenges to persistence: a harsh habitat, an unstable prey base, and potentially significant anthropogenic influences. These external factors, if combined with genetic constraints common to island populations, could be particularly difficult to withstand. To determine the genetic status of Arctic Island wolves, we used 14 microsatellite loci to estimate population variation and the extent of inter-island and island-mainland gene flow. All island populations were significantly less variable than mainland wolves; although inbreeding is currently insignificant, the two least variable populations, Banks and the High Arctic (Ellesmere and Devon Islands), showed genetic signatures of recent population declines. Recovery after a bottleneck appears to result, in large part, via recolonization from other islands. These extinction-recolonization dynamics, and the degree of similarity among island wolves revealed by Bayesian clustering, suggest that Arctic Island wolves function as a metapopulation. Persistence of the metapopulation may be supported by periodic migration from mainland populations, occurring primarily through two corridors: Baffin Island in the Eastern Arctic, and Victoria Island in the Western Arctic. This gene flow could be compromised or eliminated by loss—due to climatic warming or increased human activity—of sea ice in the Northwest Passage. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Exchange diffusion of dopamine induced in planar lipid bilayer membranes by the ionophore X537A

The ionophore X537A causes a large increase in the [(14)C]dopamine (a catecholamine) permeability of planar bilayer membranes. Dopamine transport increases linearly with the ionophore concentration. At relatively high concentrations in the presence of dopamine, the ionophore omdices a conductance which is nearly ideally selective for the dopamine cation. However, the total dopamine flux as determined in tracer experiments is not affected by an electric field and is over 10(5) times larger than predicted from the estimated dopamine conductance. Increasing the dopamine concentration on the side containing radioactive dopamine (the cis side) saturates the dopamine transport. This saturation is relieved by trans addition of nonradioactive dopamine, tyramine, H(+), or K(+). With unequal concentrations of dopamine cis and trans (49 and 12.5 mM), the unidirectional dopamine fluxes are equal. Increasing H(+) cis and trans decreases dopamine transport. It is concluded that at physiological pH, the X537A-induced transport of dopamine occurs via an electrically silent exchange diffusion of dopamine cation with another cation (e.g., dopamine(+), H(+), or K(+)). X537A induces a Ca(++)-independent release of catecholamines from sympathetic nerves by interfering with intracellular storage within storage vesicles (R.W. Holz. 1975. Biochim. Biophys. Acta. 375:138-152). It is suggested that X537A causes an exchange of intravesicular catecholamine with a cytoplasmic cation (perhaps K(+) or H(+)) across the storage vesicle membrane.     

Benzidine-based dyes: effects of industrial practices,regulations, and world trade on the biological stains market

One of the most sweeping changes in the dye industry since the advent of synthetic dyes grew out of the health risks associated with benzidine. Dyes made from benzidine and its derivatives were used around the world until adverse health effects become incontrovertible. Workers and family members of workers involved in production and use of benzidine-based dyes had a high incidence of bladder cancer. Following publication of several reports documenting this health hazard, dye makers in the USA, Europe, and Japan phased these dyes out of production in the 1970s. Government regulations lent legal support for these voluntary initiatives. Two strategies subsequently evolved to compensate: developed nations brought alternative substances to market while emerging countries increased production of carcinogenic dyes and sold them at discount prices around the world. Nearly all dye manufacturing now has moved away from nations whose costs of production and compliance rendered them unable to compete. The purpose of this brief review is to publicize the health risks associated with dyes made from benzidine and its congeners, and to alert all companies and end users handling these dyes for biomedical applications that composition of the product and lot-to-lot variability may be problematic because of the manufacturing and distribution practices of the countries where they are produced.