Time Refraction of Spin Waves

We present an experimental study of time refraction of spin waves (SWs) propagating in microscopic waveguides under the influence of time-varying magnetic fields. Using space- and time-resolved Brillouin light scattering microscopy, we demonstrate that the broken translational symmetry along the time coordinate results in a loss of energy conservation for SWs and thus allows for a broadband and controllable shift of the SW frequency. With an integrated design of SW waveguide and microscopic current line for the generation of strong, nanosecond-long, magnetic field pulses, a conversion efficiency up to 39% of the carrier SW frequency is achieved, significantly larger compared to photonic systems. Given the strength of the magnetic field pulses and its strong impact on the SW dispersion relation, the effect of time refraction can be quantified on a length scale comparable to the SW wavelength. Furthermore, we utilize time refraction to excite SW bursts with pulse durations in the nanosecond range and a frequency shift depending on the pulse polarity.

Large Spin-Wave Bullet in a Ferrimagnetic Insulator Driven by the Spin Hall Effect

Because of its transverse nature, spin Hall effects (SHE) provide the possibility to excite and detect spin currents and magnetization dynamics even in magnetic insulators. Magnetic insulators are outstanding materials for the investigation of nonlinear phenomena and for novel low power spintronics applications because of their extremely low Gilbert damping. Here, we report on the direct imaging of electrically driven spin-torque ferromagnetic resonance (ST-FMR) in the ferrimagnetic insulator Y_{3}Fe_{5}O_{12} based on the excitation and detection by SHEs. The driven spin dynamics in Y_{3}Fe_{5}O_{12} is directly imaged by spatially resolved microfocused Brillouin light scattering spectroscopy. Previously, ST-FMR experiments assumed a uniform precession across the sample, which is not valid in our measurements. A strong spin-wave localization in the center of the sample is observed indicating the formation of a nonlinear, self-localized spin-wave "bullet".

Universal method for separating spin pumping from spin rectification voltage of ferromagnetic resonance

We develop a method for universally resolving the important issue of separating spin pumping from spin rectification signals in bilayer spintronics devices. This method is based on the characteristic distinction of spin pumping and spin rectification, as revealed in their different angular and field symmetries. It applies generally for analyzing charge voltages in bilayers induced by the ferromagnetic resonance (FMR), independent of FMR line shape. Hence, it solves the outstanding problem that device-specific microwave properties restrict the universal quantification of the spin Hall angle in bilayer devices via FMR experiments. Furthermore, it paves the way for directly measuring the nonlinear evolution of spin current generated by spin pumping. The spin Hall angle in a Py/Pt bilayer is thereby directly measured as 0.021±0.015 up to a large precession cone angle of about 20°.

Unanticipated proximity behavior in ferromagnet-superconductor heterostructures with controlled magnetic noncollinearity

Magnetization noncollinearity in ferromagnet-superconductor (F/S) heterostructures is expected to enhance the superconducting transition temperature (T(c)) according to the domain-wall superconductivity theory, or to suppress T(c) when spin-triplet Cooper pairs are explicitly considered. We study the proximity effect in F/S structures where the F layer is a Sm-Co/Py exchange-spring bilayer and the S layer is Nb. The exchange-spring contains a single, controllable and quantifiable domain wall in the Py layer. We observe an enhancement of superconductivity that is nonmonotonic as the Py domain wall is increasingly twisted via rotating a magnetic field, different from theoretical predictions. We have excluded magnetic fields and vortex motion as the source of the nonmonotonic behavior. This unanticipated proximity behavior suggests that new physics is yet to be captured in the theoretical treatments of F/S systems containing noncollinear magnetization.

Thermoelectric detection of spin waves

We report on the thermoelectric detection of spin waves in Permalloy stripes via the anomalous Nernst effect. Spin waves are locally excited by a dynamic magnetic field generated from a microwave current flowing in a coplanar waveguide placed on top of a Permalloy stripe, which acts as a waveguide for spin waves. Electric contacts at the ends of the Permalloy stripe measure a dc voltage generated along the stripe. Magnetic field sweeps for different applied microwave frequencies reveal, with a remarkable signal-to-noise ratio, an electric voltage signature characteristic of spin-wave excitations. The symmetry of the signal with respect to the applied magnetic field direction indicates that the anomalous Nernst effect is responsible; Seebeck effects, anisotropic magnetoresistance, and voltages due to spin-motive forces are excluded. The dissipation of spin waves causes local heating that drains into the substrate, giving rise to a temperature gradient perpendicular to the sample plane, resulting in the anomalous Nernst voltage.

Direct determination of energy level alignment and charge transport at metal-Alq3 interfaces via ballistic-electron-emission spectroscopy

Using ballistic-electron-emission spectroscopy (BEES), we directly determined the energy barrier for electron injection at clean interfaces of Alq(3) with Al and Fe to be 2.1 and 2.2 eV, respectively. We quantitatively modeled the sub-barrier BEES spectra with an accumulated space charge layer, and found that the transport of nonballistic electrons is consistent with random hopping over the injection barrier.

Complex patterns in a simple system

Numerical simulations of a simple reaction-diffusion model reveal a surprising variety of irregular spatiotemporal patterns. These patterns arise in response to finite-amplitude perturbations. Some of them resemble the steady irregular patterns recently observed in thin gel reactor experiments. Others consist of spots that grow until they reach a critical size, at which time they divide in two. If in some region the spots become overcrowded, all of the spots in that region decay into the uniform background.

Surface spin flip probability of mesoscopic Ag wires

Spin relaxation in mesoscopic Ag wires in the diffusive transport regime is studied via nonlocal spin valve and Hanle effect measurements performed on Permalloy/Ag lateral spin valves. The ratio between momentum and spin relaxation times is not constant at low temperatures. This can be explained with the Elliott-Yafet spin relaxation mechanism by considering the momentum surface relaxation time as being temperature dependent. We present a model to separately determine spin flip probabilities for phonon, impurity and surface scattering and find that the spin flip probability is highest for surface scattering.

Quantifying spin Hall angles from spin pumping: experiments and theory

Spin Hall effects intermix spin and charge currents even in nonmagnetic materials and, therefore, ultimately may allow the use of spin transport without the need for ferromagnets. We show how spin Hall effects can be quantified by integrating Ni{80}Fe{20}|normal metal (N) bilayers into a coplanar waveguide. A dc spin current in N can be generated by spin pumping in a controllable way by ferromagnetic resonance. The transverse dc voltage detected along the Ni{80}Fe{20}|N has contributions from both the anisotropic magnetoresistance and the spin Hall effect, which can be distinguished by their symmetries. We developed a theory that accounts for both. In this way, we determine the spin Hall angle quantitatively for Pt, Au, and Mo. This approach can readily be adapted to any conducting material with even very small spin Hall angles.

Negative nonlocal resistance in mesoscopic gold Hall bars: absence of the giant spin Hall effect

We report the observation of negative nonlocal resistances in multiterminal mesoscopic gold Hall bar structures whose characteristic dimensions are larger than the electron mean-free path. Our results can only be partially explained by a classical diffusive model of the nonlocal transport, and are not consistent with a recently proposed model based on spin Hall effects. Instead, our analysis suggests that a quasiballistic transport mechanism is responsible for the observed negative nonlocal resistance. Based on the sensitivity of our measurements and the spin Hall effect model, we find an upper limit for the spin Hall angle in gold of 0.023 at 4.5 K.

An investigation of models of the IP3R channel in Xenopus oocyte

We consider different models of inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R) channels in order to fit nuclear membrane patch clamp data of the stationary open probability, mean open time, and mean close time of channels in the Xenopus oocyte. Our results indicate that rather than to treat the tetrameric IP(3)R as four independent and identical subunits, one should assume sequential binding-unbinding processes of Ca(2+) ions and IP(3) messengers. Our simulations also favor the assumption that a channel opens through a conformational transition from a close state to an active state.

Magnetic instability regions in patterned structures: influence of element shape on magnetization reversal dynamics

We report a time-resolved imaging study of the influence of shape on magnetic instabilities in patterned magnetic structures. We find that in rectangular structures magnetization reversal initiates at the ends and interior simultaneously, while in structures with tapered ends the reversal begins in the middle of the structures and spreads out to the ends. The degree of tapering is important for both the switching field and the time required for full reversal. A model based on the concept of local instability regions yields good agreement with the observed location of the reversal onsets.

Regulatory constraints for the transport of samples and compliance with the World Organisation for Animal Health (OIE) standards for biosecurity and biocontainment

The International Regulations for transport of infectious substances, including diagnostic specimens, are based on the United Nations Model Regulations and are the standard for transport by all means of transportation including air transport; the International Air Transport Association (IATA) regulation specifically addresses air shipment. In 2005 and 2006 there were major improvements in the procedures for shipping infectious substances. These substances are divided into Category A, which includes primarily cultures of the more pathogenic agents and Category B, all the other substances. Category A shipments must have a Dangerous Goods Certificate and meet other requirements. Category B shipments, which include most diagnostic tissue specimens, do not. These regulations specifically exempt certain substances, including those that have been neutralized or inactivated to destroy pathogens and samples from "normal" animals. The packaging requirements help insure that biocontainment is maintained during shipment to protect the shipper and the environment. The packaging requirements and the shipping procedures provide a chain of custody and assist in supporting biosecurity. The more stringent Category A requirements provide increased biocontainment and biosecurity safeguards for these potentially more dangerous substances. In addition, National requirements, such as import permits and the US select agent requirements, provide an added measure of biocontainment and biosecurity.

Worldwide risks of animal diseases: introduction

Animal diseases impact food supplies, trade and commerce, and human health and well-being in every part of the world. Outbreaks draw the attention of those in agriculture, regulatory agencies, and government, as well as the general public. This was demonstrated by the 2000-2001 foot and mouth disease (FMD) outbreaks that occurred in Europe, South America, Asia and Africa and by the recent increased occurrence of emerging diseases transmitted from animals to humans. Examples of these emerging zoonotic diseases are highly pathogenic avian influenza, bovine spongiform encephalopathy, West Nile virus and severe acute respiratory syndrome. There is also the risk of well-known and preventable zoonotic diseases, such as rabies, brucellosis, leishmaniasis, and echinococcosis/hydatidosis, in certain countries; these diseases have a high morbidity with the potential for a very high mortality. Animal agriculturalists should have a global disease awareness of disease risks and develop plans of action to deal with them; in order to better respond to these diseases, they should develop the skills and competencies in politics, media interactions, and community engagement. This issue of Veterinaria Italiana presents information on the risk of animal diseases; their impact on animals and humans at the international, national, industry, and societal levels; and the responses to them. In addition, specific information is provided on national and international disease monitoring, surveillance and reporting, the risk of spread of disease by bioterrorism and on import risk analysis.

Cu2O island shape transition during Cu-Au alloy oxidation

In situ transmission electron microscopy observations of the oxidation of (001) Cu-Au alloys indicate that the Cu2O islands that form undergo a remarkable transformation from an initially compact morphology to a dendritic structure as growth proceeds. Correspondingly, the surface composition becomes nonuniform and the fractal dimension associated with the islands evolves from 2.0 to a stable value of 1.87, indicating a transition in the rate-limiting mechanism of oxidation from oxygen surface diffusion to diffusion of copper through the increasingly gold-rich regions adjacent to the islands.

Transportation of reagents, reference materials and samples: the international perspective

The International Regulations for the transport of infectious substances, which could include reagents, reference material and samples, are based on the 13th revision of the United Nations Model Regulations and are the standard for transport of infectious substances by all means of transportation. The 13th revision, effective January 2005 and further amended in March and July 2005, made major improvements in these shipping regulations. They specifically exempt certain substances, including those that have been neutralized or inactivated to destroy any pathogens and samples from "normal" animals. Infectious substances are divided into Category A, which includes primarily cultures of the more pathogenic agents and Category B, which includes all other substances that do not meet the Category A criteria. Tissue specimens, submitted for diagnosis, are included in Category B. Category A shipments must have a Dangerous Goods Certificate and meet other requirements; Category B shipments do not. The National requirements, such as import permits, and certain airline restrictions must also be met.

Office International des Epizooties international standards for bluetongue

Preventing the spread of disease through international trade is one of the primary objectives of the Office International des Epizooties (OIE), the World Organisation for Animal Health. This is accomplished by establishing international standards that facilitate trade while minimising the risk of introducing diseases such as bluetongue (BT). The OIE standards for BT are contained in the Terrestrial animal health code (Code) and the Manual of diagnostic tests and vaccines for terrestrial animals (Manual). These standards include procedures for prompt reporting of BT outbreaks; requirements that should be met for a country or zone to be defined as free of bluetongue virus (BTV); recommendations for the safe importation of live animals, semen and embryos into a BTV-free country or zone; and the general provisions that countries should meet to reduce the risk of spread of BTV through trade. The Manual describes in detail the various tests for the diagnosis of BT. It provides a list of prescribed tests; these are the tests that are required by the Code for the testing of animals in connection with international trade. There are 24 serotypes of BTV and infected countries have the right to restrict imports from countries that have different types of BTV. However, this should only be done if a surveillance and monitoring programme has confirmed that the other types are not present. Zoning for an arbovirus is difficult to apply but zoning for vectors is practicable. Some countries have demonstrated that there is no evidence of infection in their country or parts of their country even though there has been unrestricted animal movement between endemic zones and free zones. This freedom is due to the absence of vectors in the free zone. Based on this observation, free countries and zones can be established if an appropriate surveillance and monitoring programme is in place to define their boundaries. Consequently, there have been extensive changes in the Code to allow the establishment of BTV-free countries and zones and seasonally free countries and zones to provide the basis for safe trade, while minimising the risk of the introduction of BTV.

Distribution of bluetongue in the United States of America, 1991-2002

Bluetongue virus (BTV) distribution in the United States of America (USA) is limited by the range of the vector Culicoides spp. Regional differences exist with the north-eastern states being free of BTV, while the central and north-western states are seasonally free of virus. Activity of the virus can be observed throughout the year in the southern USA. Serological evidence defining the distribution of BTV in selected regions of the USA is gathered regularly through serological surveys conducted on samples from slaughter cattle. From 1991 to 2002, ten serological surveys were completed. Results from Alaska, Hawaii, Michigan, Minnesota, New York, Wisconsin and New England consistently demonstrated a seropositive rate of less than 2%, confirming BTV-free status. Antibody against BTV was sporadically detected in cattle originating from states contiguous to the BTV-free regions. Additional information on BTV distribution in the USA is obtained through identification of BTV or BTV RNA in diagnostic, surveillance and export specimens submitted to the National Veterinary Services Laboratories. Results confirm that BTV serotypes 2, 10, 11, 13 and 17 are present in the USA.

International Standards for the Control of Avian Influenza

The Office International des Epizooties (OIE) has developed international standards to reduce the risk of the spread of high-pathogenicity avian influenza though international trade. These standards include providing a definition of high-pathogenicity avian influenza (HPAI), procedures for prompt reporting of HPAI outbreaks, requirements that must be met for a country or zone to be defined as free of HPAI, requirements that should be met to import live birds and avian products into a HPAI-free country or zone, and the general provisions that countries should meet to reduce the risk of spread of HPAI through trade. The goal of these standards is to facilitate trade while minimizing the risk of the introduction of HPAI.

Cadaveric Tissue Supply to the Commercial Sector For Research: Collaboration between NHS Pathology and NBS Tissue Services in the U.K., Extending the Options for Donors

The Peterborough Hospital Human Tissue Bank (PHHTB) and National Blood Service Tissue Services (London and South East Zone) (NBSTS) operate within the U.K. National Health Service (NHS) and have a system in place to retrieve cadaveric tissues for commercial sector research. The collaboration meets the aims of PHHTB and NBSTS and is legal, ethical and safe. This paper presents the results of the first 20 successful retrievals referred from NBSTS to PHHTB. Cadaveric retrieval of tissue for research extends the options for donors and their relatives. The research option is particularly welcomed in cases where clinical retrieval for tissue transplantation is contraindicated. We believe the system is applicable to other centres.

Experimental observation of disorder-driven hysteresis-loop criticality

We have studied the effect of magnetic disorder on the magnetization reversal process in thin Co/CoO films. The antiferromagnetic CoO layer allows a reversible tuning of the magnetic disorder by simple temperature variation. For temperatures above a critical temperature T(c), we observe a discontinuous magnetization reversal, whereas smooth magnetization loops occur for T<T(c). Our measurements establish the existence of a disorder-driven critical point in the nonequilibrium phase diagram. In addition, we observe scaling behavior in the vicinity of the critical point and determine the critical exponents beta = 0.022+/-0.006 and betadelta = 0.30+/-0.03 for this two-dimensional system.

Fire-diffuse-fire model of dynamics of intracellular calcium waves

When Ca2+ is released from internal stores in living cells, the resulting wave of increased concentration can travel without deformation (continuous propagation) or with burst-like behavior (saltatory propagation). We analyze the "fire-diffuse-fire" model in order to illuminate the differences between these two modes of propagation. We show that the Ca2+ release wave in immature Xenopus oocytes and cardiac myocytes is saltatory, whereas the fertilization wave in the mature oocyte is continuous.

A new solid-phase support for oligonucleotide synthesis

An alternative solid support for oligonucleotide synthesis was developed by coupling a polymer colloid to a modified polyethylene filter disc. The functions on the polymer colloid not used for attachment to the surface were derivatized with a Jeffamine diamine and loaded with appropriate deoxynucleoside succinates. The performance of this support system was evaluated and compared to existing resins.

Surface plasmon resonance: a study of the effect of biotinylation on the selection of antibodies for use in immunoassays

Surface plasmon resonance is a valuable optical phenomenon for monitoring biomolecular interactions in real time. In this project anti-mouse-Fc was coupled to the carboxymethyl dextran coating on the surface of a CM5 sensor chip (BIAcore) using amine coupling. Monoclonal antibodies (MAbs) to Luteinizing Hormone (LH) were then captured on this surface in the correct orientation for binding. LH (500 IU/l) was injected over the surface and the subsequent binding and dissociation events were monitored. The resulting optical response curves allowed fast analysis of the binding interactions of eight selected MAbs. It was possible to develop a two-site immunometric assay for LH using a pair of these MAbs. The effect of biotinylating the MAbs, using various biotin:antibody coupling ratios, on their subsequent binding to both LH and avidin conjugated alkaline phosphatase was also investigated. This approach has allowed rapid evaluation of the effect of changes in both reagent and reaction conditions on immunoassay performance and appears to be a valuable adjunct to immunosensor and immunoassay development.

Saltatory propagation of Ca2+ waves by Ca2+ sparks

Punctate releases of Ca2+, called Ca2+ sparks, originate at the regular array of t-tubules in cardiac myocytes and skeletal muscle. During Ca2+ overload sparks serve as sites for the initiation and propagation of Ca2+ waves in myocytes. Computer simulations of spark-mediated waves are performed with model release sites that reproduce the adaptive Ca2+ release observed for the ryanodine receptor. The speed of these waves is proportional to the diffusion constant of Ca2+, D, rather than D, as is true for reaction-diffusion equations in a continuous excitable medium. A simplified "fire-diffuse-fire" model that mimics the properties of Ca2+-induced Ca2+ release (CICR) from isolated sites is used to explain this saltatory mode of wave propagation. Saltatory and continuous wave propagation can be differentiated by the temperature and Ca2+ buffer dependence of wave speed.

Central or national veterinary diagnostic laboratories

Information on laboratory organisational structure and roles was gathered from twenty-four national veterinary diagnostic laboratories around the world. This information was used to develop an overview of the organisation and roles of the national veterinary diagnostic laboratory. In addition, the national diagnostic laboratory for the United States of America (the National Veterinary Services Laboratories) was used as an example to provide more information on the activities of such a laboratory. The survey revealed great variation in organisation and structure among the twenty-four laboratories. A few have only one facility, others function at multiple locations, and all have different supervisory reporting systems. However, these laboratories all form a significant part of the national veterinary infrastructure. All of the laboratories contacted in the survey report to (or are at least partially under the direction of) the Chief Veterinary Officer or another senior animal health official, and most report to the Ministry of Agriculture. The national veterinary diagnostic laboratories have similar roles, and are all responsible for foreign animal disease diagnosis and for providing support to national disease eradication or control programmes. Most also play an active role in import and export testing, either performing the tests themselves or developing a quality assurance programme for other laboratories that perform the testing. In addition, the national veterinary diagnostic laboratories usually undertake research and provide training, consultation, disease surveillance information and, in some cases, vaccine evaluation.

Survey of the hemagglutinin (HA) cleavage site sequence of H5 and H7 avian influenza viruses: amino acid sequence at the HA cleavage site as a marker of pathogenicity potential

The deduced amino acid sequence at the hemagglutinin (HA) cleavage site of 76 avian influenza (AI) viruses, subtypes H5 and H7, was determined by reverse transcription-polymerase chain reaction and cycle sequencing techniques to assess pathogenicity. Eighteen of the 76 viruses were isolated in 1993 and 1994 from various sources in the United States. In addition, 34 H5 (4 highly pathogenic [HP] and 30 non-highly pathogenic [non-HP]) and 24 H7 (3 HP and 21 non-HP) repository viruses, isolated between 1927 and 1992, were sequenced and the sequences compared to those in recent isolates. All repository HP H5 and H7 viruses studied had multiple basic amino acids adjacent to the HA cleavage site and most had basic amino acids in excess of the proposed minimum motif B-X-B-R (B = basic amino acids arginine or lysine, X = nonbasic amino acid, R = arginine) that has been associated with high pathogenicity. Of the non-HP viruses studied, 35 of 38 for H5 and 30 of 31 for H7 conformed to the motif B-X-X-R and B-X-R, respectively. Two non-HP H5 viruses had the motif X-X-X-R at the cleavage site and a third had the motif B-X-X-K (K = basic amino acid lysine). One non-HP H7 (A/Pekin robin/CA/30412-5/94) had four basic amino acids (K-R-R-R) adjacent to the cleavage site. Although the Pekin robin isolate did not produce disease in chickens under the conditions of the study it did have the amino acid sequence compatible with that in HP AI viruses and, therefore, is considered potentially HP. This is the first account of an H7 virus that is non-HP in chickens but meets the molecular criterion to be classified as HP.

Susceptibility of pigeons to avian influenza

Susceptibility to infection with avian influenza virus (AIV) was studied in pigeons inoculated via oculonasal (Experiment 1) or intravenous (Experiment 2) route. Chickens were included as susceptible hosts in both experiments. Two subtypes each of the highly pathogenic AIV (HPAIV; HP CK/PA H5N2 and HP CK/Australia H7N7) and non-pathogenic AIV (NPAIV; NP CK/PA H5N2 and NP emu/TX H7N1) at a dose of 10(5) embryo infective dose per bird were used as inoculum. The pigeons inoculated with HP CK/PA H5N2 or HP CK/Australia H7N7 remained apparently healthy throughout the 21-day observation period, did not shed viruses on 3, 7, 14, and 21 days postinoculation (DPI), and had no demonstrable levels of antibodies on 21 DPI. On the other hand, 9 of 12 chickens inoculated with the HPAIV died of highly pathogenic avian influenza; the viruses were recovered from their respiratory and intestinal tissues, and the surviving chickens had antibodies to AIV. Regarding responses of pigeons to inoculation with NP CK/PA H5N2 or NP emu/TX H7N1, the pigeons remained clinically healthy throughout the 21-day observation period and did not have detectable levels of antibodies on 21 DPI; only one pigeon yielded the NP emu/TX H7N1 on 3 DPI. The virus was isolated from a tracheal swab and was believed to be the residual inoculum virus. Based on the responses of pigeons to NPAIV and HPAIV, it was concluded that the pigeons were resistant or minimally susceptible to infection with HPAIV or NPAIV.

Comparison of Newcastle disease viruses isolated from cormorants in Canada and the USA in 1975, 1990 and 1992

Seventeen Newcastle disease virus (NDV) isolates obtained from cormorants, turkeys, a pelican, and a gull in Canada and the USA collected in 1975, 1990 and 1992 were analyzed for relatedness by monoclonal antibody profiling. In addition, nucleotide sequence analysis was performed in two areas of the fusion (F) gene for 5 of the isolates. No difference in the antigenicity of these 17 viruses, as determined by monoclonal antibody binding patterns, was seen. The amino acid sequences obtained via nucleotide sequencing at the cleavage site of the F protein showed that all the isolates tested had two pairs of basic amino acids immediately upstream of the cleavage site, and a phenylalanine residue at the N-terminus of the F1 protein, which is consistent with velogenic NDV. The deduced amino acid sequence obtained at the cleavage site of the F protein from 6 of the isolates was virtually identical regardless of the species, year of isolation, or location. However, the 1975 cormorant isolate showed marked differences from the 1990-1992 isolates in the nucleotide and deduced amino acid sequence of the F gene signal region. These data indicate that the 1990 and 1992 outbreaks were caused by the same epizootic virus and further suggest that the population of NDV in these wild birds may be very stable. The belief that the velogenic NDV circulating in cormorants in 1992 was transmitted into the free-ranging turkey flocks located near the cormorants in North Dakota is supported by the present study in which no distinction could be made between the viruses isolated from turkeys or wild birds.

Probable epizootic chlamydiosis in wild California (Larus californicus) and ring-billed (Larus delawarensis) gulls in North Dakota

During the summer of 1986, more than 400 California gulls (Larus californicus) and ring-billed gulls (Larvus delawarensis), primarily fledglings, died on an island in Lake Sakakawea near New Town, North Dakota (USA). Mortality was attributed largely to chlamydiosis. Necropsy findings in nine carcasses included splenomegaly (n = 9), hepatomegaly (n = 4), and pericarditis (n = 1). Livers from three California gulls and two ring-billed gulls, and spleens from the same five birds plus a third ring-billed gull were positive for Chlamydia psittaci by the direct immunofluorescence test. Chlamydia psittaci was isolated from separate pools of liver and spleen from one California gull and one ring-billed gull. This is believed to be the first record of epizootic chlamydiosis in gulls and the second report of epizootic chlamydial mortality in wild birds in North America.

Comparison of polymerase chain reaction and virus isolation for detection of epizootic hemorrhagic disease virus in clinical samples from naturally infected deer

We compared our recently reported reverse transcriptase polymerase chain reaction (PCR)-based assay for detection of epizootic hemorrhagic disease virus (EHDV) in clinical samples with different virus isolation (VI) procedures. Thirty-six blood samples and 1 spleen sample from deer were assessed by the EHDV PCR assay and VI in baby hamster kidney (BHK)-21 cells and embryonated chicken eggs (ECE). The EHDV PCR assay detected EHDV RNA from 6 blood samples obtained from deer during 1988-1989 outbreaks of epizootic hemorrhagic disease and from the spleen and blood samples of a deer with clinical hemorrhagic disease in 1992. The 6 blood samples from the 1988-1989 outbreaks and the spleen sample from the 1992 case were VI positive on BHK-21 cell culture. The blood from the same deer with the PCR- and VI-positive spleen was VI negative in BHK-21 cells and ECE. All EHDV isolates were identified as EHDV serotype 2 by a plaque inhibition test. The results of this study indicate that the sensitivity of the previously described EHDV PCR assay is comparable to or greater than that of the VI method in BHK-21 cell culture or ECE. The EHDV PCR assays could provide a superior diagnostic alternative to the current cumbersome and time-consuming VI procedures.

Presence of avian influenza virus (AIV) subtypes H5N2 and H7N1 in emus (Dromaius novaehollandiae) and rheas (Rhea americana): virus isolation and serologic findings

Avian influenza virus (AIV) subtypes H5N2 and H7N1 were isolated from emus (Dromaius novaehollandiae) and rheas (Rhea americana) in Texas and North Carolina. All the rheas and emus had a history of respiratory disease except one emu, which was clinically normal. The isolates were not pathogenic for chickens and turkeys under the conditions of the experiment. Humoral antibodies to all known hemagglutinin (H) subtypes except H10, H13, and H14 and to all nine neuraminidase (N) subtypes were found in emus and rheas in 11 states. Therefore, emus and rheas are susceptible to infection with several AIV subtypes.

Diagnosis of eastern equine encephalomyelitis virus infection in horses by immunoglobulin M and G capture enzyme-linked immunosorbent assay

Immunoglobulin M (IgM) and G (IgG) capture enzyme-linked immunosorbent assays (ELISAs) were used as possible adjuncts to hemagglutination inhibition (HI) and virus neutralization (VN) tests to differentiate between reaction to recent exposure to eastern equine encephalomyelitis (EEE) virus and those due to prior vaccination. Serum samples were evaluated by the IgM-capture ELISA, and the results were compared with those of HI and VN tests. Of 381 serum samples, 51% (195 samples) were positive by HI test (> or = 1:40) and 54% (205 samples) were positive by VN test (> or = 1:10), but only 35% (132 samples) were positive by IgM-capture ELISA (> or = 1:100). With only a few exceptions, the sera with IgG ELISA titers had a VN titer of > or = 1:100. When EEE virus isolation and serology were compared, the EEE cases were divided into three categories: 1) peracute cases--the serum was negative for EEE IgM and IgG by the ELISA, negative for VN antibody, but HI antibody positive; 2) acute cases--IgM and HI antibody positive but negative for IgG and VN antibody; and 3) transitional cases--positive for IgM and IgG antibodies, HI titers of 1:40-1:160, and VN titers of > or = 1:100. IgM antibodies of EEE virus were monospecific and did not cross-react with western or Venezuelan equine encephalomyelitis viral antigens by the ELISA.(ABSTRACT TRUNCATED AT 250 WORDS)

Occurrence of velogenic viscerotropic Newcastle disease in pet and exotic birds in 1991

In 1991, velogenic viscerotropic Newcastle disease (VVND) was diagnosed in domestic psittacine birds in six states: Illinois, Indiana, Michigan, Texas, California, and Nevada. In the first four states, the disease assumed outbreak proportions. The affected psittacine birds--yellow-headed Amazon parrots (Amazona ochrocephala oratrix), yellow-naped Amazon parrots (Amazona ochrocephala auropalliata), cockatiels (Nymphicus hollandicus), and conures (unknown species)--exhibited respiratory and/or central nervous system signs. The velogenic viscerotropic Newcastle disease virus (VVNDV) was isolated from cloacal and tracheal swabs and various tissues, such as the lung, trachea, distal intestine, and spleen. The origin of the birds could not be established. The disease in the six states was promptly controlled, with no evidence that domestic poultry had been exposed. Also, VVNDV was isolated from quarantined birds intended for importation into the United States. Included were 53 moustached parakeets (Psittacula alexandri fasciata), a mynah (Gracula religiosa), a drongo (Dicrurus sp.), and three partridges (family Phasianidae). Groups of birds that yielded VVNDV were denied entry into the United States. Birds that are illegally imported and therefore not tested for the presence of foreign animal pathogens are a potential source of VVNDV and a threat to domestic poultry and caged birds.

Hog cholera diagnostic techniques

Clinical signs and lesions can sometimes provide the basis for a presumptive diagnosis of hog cholera (HC). However, an accurate diagnosis requires laboratory testing. The usual procedure for the detection of viral antigen is the examination of cryostat sections stained with fluorescein-conjugated HC antiserum. A more definitive technique is isolation of the virus in PK-15 cell cultures and identification of the viral antigen in cells using an HC fluorescent antibody conjugate. As bovine viral diarrhea (BVD) virus will cross-react with HC virus, isolation must be confirmed by the comparison of BVD and HC staining or, preferably, by the use of monoclonal antibodies that can differentiate between HC and BVD viruses. Hog cholera surveillance must rely on serology. The fluorescent antibody virus neutralization (FAVN) test is the classical technique, and HC and BVD antibody can usually be differentiated if HC-positive serum samples are tested against both viruses. Recently the enzyme-linked immunosorbent assay (ELISA) and peroxidase-labeled antibody tests have become the commonly used techniques.

Competitive ELISA for serodiagnosis of bluetongue: evaluation of group-specific monoclonal antibodies and expressed VP7 antigen

The performance of 2 competitive enzyme-linked immunosorbent assays (C-ELISA) was compared with the reference C-ELISA I for the detection of antibodies to bluetongue virus (BTV). One of the assays (C-ELISA II) used a group-specific monoclonal antibody (MAb) to BTV, obtained from the American Type Culture Collection (8A3B-6) and tissue culture (TC)-derived BTV antigen (Ag), and the other assay (C-ELISA III) used BTV core protein VP7 (expressed in yeast) and the reference MAb (Pirbright Laboratory, 3-17-A3). Test sera were obtained by sequential blood samples from 22 calves, each inoculated with a different serotype (T) of BTV (South African [SA] T-1-T-16 and T-18-T-20 and USA T-11, T-13, and T-17). Sera were also obtained from 4 calves and 4 sheep inoculated with USA BTV T-10 and from several groups of calves exposed to single or multiple doses of epizootic hemorrhagic disease virus (EHDV) T-1-T-4 grown in TC (BHK-21) or suckling mouse brain (SMB). A total of 618 bovine and ovine field sera collected from BT-free and BT-endemic areas were also tested. The C-ELISA III was more sensitive than the C-ELISA II in the detection of anti-BTV antibody in sera from cattle and sheep early after infection with BTV. Seroconversion was demonstrated by the 3 C-ELISAs in all animals inoculated with BTV by 20 days postinfection (DPI), except in calves that received SA T-3 or USA T-13, which became positive at 40 DPI.(ABSTRACT TRUNCATED AT 250 WORDS)