Showing papers by "Justin C. Brown published in 2007"

Persistence of h5 and h7 avian influenza viruses in water

Abstract: Although fecal-oral transmission of avian influenza viruses (AIV) via contaminated water represents a recognized mechanism for transmission within wild waterfowl populations, little is known about viral persistence in this medium. In order to provide initial data on persistence of H5 and H7 AIVs in water, we evaluated eight wild-type low-pathogenicity H5 and H7 AIVs isolated from species representing the two major influenza reservoirs (Anseriformes and Charadriiformes). In addition, the persistence of two highly pathogenic avian influenza (HPAI) H5N1 viruses from Asia was examined to provide some insight into the potential for these viruses to be transmitted and maintained in the environments of wild bird populations. Viruses were tested at two temperatures (17 C and 28 C) and three salinity levels (0, 15, and 30 parts per thousand sea salt). The wild-type H5 and H7 AIV persistence data to date indicate the following: 1) that H5 and H7 AIVs can persist for extended periods of time in water, with a duration of infectivity comparable to AIVs of other subtypes; 2) that the persistence of H5 and H7 AIVs is inversely proportional to temperature and salinity of water; and 3) that a significant interaction exists between the effects of temperature and salinity on the persistence of AIV, with the effect of salinity more prominent at lower temperatures. Results from the two HPAI H5N1 viruses from Asia indicate that these viruses did not persist as long as the wild-type AIVs.

Wild birds and the epidemiology of avian influenza

Abstract: Although wild birds are the recognized source and reservoir for all subtypes of avian influenza viruses (AIV), the complex interaction among these diverse host and virus populations has not received adequate attention. A general concept of AIV epidemiology in wild birds exists; however, the presence of highly pathogenic avian influenza (HPAI) H5N1 viruses in wild birds has reinforced the need for a much more detailed understanding of AIV natural history. Worldwide, the wild avian reservoirs for AIV are incompletely defined, even within well-studied groups such as the Anseriformes and Charadriiformes. This lack of clarity applies not only to avian host species, but also to the various subtypes of AIV present within these populations. Even with the extensive number of AIV isolations previously reported from wild birds, the reservoir species and global distribution for many of these AIV subtypes are not completely understood. To date, studies related to AIV epidemiology in wild birds primarily focused on the agent. To move forward, we need to apply this same level of scrutiny and detailed understanding to the natural host populations and the environments they utilize. Research to date clearly demonstrates that species and population structure are important in AIV maintenance, transmission, and possibly long-distance movement. Species-related differences related to general behavior, spatial and temporal distribution, habitat utilization, migration behavior, population age structure, and individual species susceptibility all potentially influence a species' role in AIV epidemiology. The unprecedented mortality associated with HPAI H5N1 infection in wild birds provides a new window from which to view the potential for exchange of AIV between wild and domestic birds, and further demonstrates and expands the varied roles that wild birds may play in AIV epidemiology. These roles must be clearly defined if we are going understand the full implications of current HPAI H5N1 virus introduction into the wild bird populations and most importantly prevent the next one.

Susceptibility of wood ducks to H5N1 highly pathogenic avian influenza virus.

Abstract: Since 2002, H5N1 highly pathogenic avian influenza (HPAI) viruses have caused mortality in numerous species of wild birds; this is atypical for avian influenza virus (AIV) infections in these avian species, especially for species within the order Anseriformes. Although these infections document the susceptibility of wild birds to H5N1 HPAI viruses and the spillover of these viruses from infected domestic birds to wild birds, it is unknown whether H5N1 HPAI viruses can persist in free-living avian populations. In a previous study, we established that wood ducks (Aix sponsa) are highly susceptible to infection with H5N1 HPAI viruses. To quantify this susceptibility and further evaluate the likelihood of H5N1 HPAI viral maintenance in a wild bird population, we determined the concentration of virus required to produce infection in wood ducks. To accomplish this, 25 wood ducks were inoculated intranasally at 12–16 wk of age with decreasing concentrations of a H5N1 HPAI virus (A/Whooper Swan/Mongolia/244/05 [H...

Chlorine Inactivation of Highly Pathogenic Avian Influenza Virus (H5N1)

Abstract: To determine resistance of highly pathogenic avian influenza (H5N1) virus to chlorination, we exposed allantoic fluid containing 2 virus strains to chlorinated buffer at pH 7 and 8, at 5 degrees C. Free chlorine concentrations typically used in drinking water treatment are sufficient to inactivate the virus by >3 orders of magnitude.

Mechanomyographic assessment of contractile properties within seven segments of the human deltoid muscle

Abstract: The aim of this study was to determine, by a non-invasive whole muscle mechanomyographic technique (wMMG), how muscle segment contractile properties varied within the segments of the multifunctional deltoid muscle, and how such variations in contractile properties may reflect the muscle segment’s function and fibre type composition. We hypothesised that muscle segment contractile properties, consistent with slower twitch muscle fibre populations, would be associated with the deltoid’s prime mover abductor muscle segment (middle head), rather than the prime mover flexor and extensor muscle segments (anterior and posterior heads). Eighteen healthy and athletic University students (nine males and nine females; mean age 20–24 years) volunteered for this study. Each subject’s right upper limb was secured with the forearm flexed to 30° and the shoulder in 45° of abduction. The wMMG laser sensor was positioned perpendicular to the middle of each muscle segment, to record the involuntary lateral displacement of the muscle belly following a maximal, single twitch, percutaneous neuromuscular stimulation (PNS) [180 V (max.); 80 mA (max.); 50 μs]. Ten trials were recorded from each of the seven deltoid segments for a total of 70 trials per subject. From each segment, eight variables were analysed from the recorded wMMG waveforms; maximal displacement (Dmax); delay time (Td); contraction time (Tc); sustain time (Ts); relaxation time (Tr) and half relaxation time (½Tr), average rate of contraction (ARC) and the average rate of relaxation (ARR). The results indicated that the contractile properties of the seven segments of the deltoid muscle showed significant (P < 0.05) variation in a medial to lateral direction. Medially the strap-like segments of the anterior (S1, S2) and posterior heads (S4–S7), with larger moment arms for shoulder flexion and extension respectively, had the fastest contractile properties. In contrast the multipennate segment 3, with the largest moment arm for shoulder abduction, had the slowest contractile properties (P < 0.05). Muscle segment contractile properties were matched to the biomechanical and architectural characteristics of the individual muscle segments.

Extracorporeal life support for children with meningococcal septicaemia.

Abstract: Objective To describe the short-term outcome of children with meningococcal sepsis treated with extracorporeal membrane oxygenation (ECMO) in a single centre. Design Retrospective analysis of case notes. Setting The Heartlink ECMO Centre, Glenfield Hospital, Leicester. Patients Eleven children (8 boys) out of a total caseload of 800 patients were treated for meningococcal sepsis with ECMO. Interventions Extracorporeal membrane oxygenation. Results All children with meningococcal sepsis treated with ECMO had a Glasgow Meningococcal Septicaemia Prognostic Score (GMSPS) > or = 12 (positive predictive risk of death of approximately 90%). Five children had adult respiratory distress syndrome (ARDS) and six had refractory shock with multi-organ dysfunction syndrome (MODS) at presentation for ECMO. All five children in the ARDS group survived, four of five receiving veno-venous (VV-) ECMO therapy. In contrast, only one of six children with refractory shock with MODS survived, all of whom required veno-arterial (VA-) ECMO therapy. Conclusions Most children with meningococcal sepsis and severe ARDS can be successfully treated with VV-ECMO. In contrast, children with refractory shock and MODS die despite treatment with VA-ECMO. This report does not resolve whether ECMO therapy offers any advantage over conventional therapy in treating severe meningococcal sepsis.