Search

OBJECTIVE: To assess the effect of a standard decontamination and sterilization protocol employed during reuse of cardiac electrophysiology (EP) catheters on human immunodeficiency virus (HIV). SETTING: Public health viral research laboratory. METHOD(S): Studies were performed on distal, electrode-containing segments of 40 EP catheters previously used in up to 10 clinical EP procedures. EP catheter segments were immersed for 1 hour in blood contaminated with a high titer of HIV. After air drying for 2 hours, subgroups of 8 EP catheters were subjected to either (1) no treatment, (2) washing in general purpose detergent, (3) washing in enzyme cleaner, (4) sterilization in ethylene oxide, or (5) the full protocol of sequential detergent-enzyme cleaner-ethylene oxide exposure. HIV infectivity after treatment was determined by measuring HIV RNA and, in cell culture studies, assessing HIV-induced cytopathic effects (CPEs) and supernatant HIV-specific p24 antigen content. RESULT(S): With no treatment, all catheters had high HIV RNA levels associated with CPEs and high p24 antigen levels. After washing in detergent, 5 of 8 catheters had HIV RNA detected, but without CPEs or p24 antigen. HIV RNA was detected in all catheters after washing in enzyme cleaner, with CPEs and a high p24 antigen level in 1 of 8 catheters. HIV RNA, CPEs, and p24 antigen were absent after ethylene oxide. After the full protocol, HIV RNA levels were undetectable (n = 7) or low (n = 1), without evidence of CPEs or p24 antigen. CONCLUSION(S): Appropriate decontamination and sterilization of EP catheters during reuse is highly effective in inactivating HIV.

OBJECTIVE: To assess the efficacy of a standard cleaning and sterilization protocol employed during reuse of cardiac electrophysiology catheters on the infectivity of duck hepatitis B virus (DHBV; a surrogate for human hepatitis B virus), bovine viral diarrhea virus (BVDV; a surrogate for human hepatitis C virus), and human coxsackie type B3 virus (CB3). SETTING: Public health virology laboratory. METHOD(S): Studies were performed on the distal, electrode-containing segments of 120 electrophysiology catheters previously used in up to 10 clinical procedures. Catheter segments were immersed for 1 hour in blood infected with high titers of DHBV, BVDV, or CB3. After air drying for 2 hours, subgroups of 8 catheters were subjected to no treatment, washing in general-purpose detergent, washing in enzyme cleaner, sterilization in ethylene oxide, or the full protocol of sequential detergent-enzyme cleaner-ethylene oxide exposure. Presence of residual virus was assessed by nucleic acid detection and infectivity studies. RESULT(S): DHBV nucleic acid was detected on catheters after individual steps and the full protocol, whereas BVDV and CB3 nucleic acids were detected after individual steps but not the full protocol. These findings were associated with the presence of infectious DHBV and CB3, but not BVDV, on catheters after washing in detergent or enzyme cleaner. However, ethylene oxide alone or the full protocol reduced infectivity of all three viruses to undetectable levels. CONCLUSION(S): These experimental studies provide strong evidence that appropriate cleaning and sterilization of reused electrophysiology catheters inactivates blood-borne viruses such as hepatitis B and C and coxsackie type B3.

Objective: To describe the case characteristics and outcomes of patients hospitalised with pandemic (H1N1) 2009 influenza infection during the first 2 months of the epidemic. Design, participants and setting: Prospective case series of 112 patients admitted to seven hospitals in Melbourne with laboratory-confirmed pandemic (H1N1) 2009 influenza between 1 May and 17 July 2009. Main Outcome Measure(s): Details of case characteristics, risk factors for severe disease, treatment and clinical course. Result(s): Of 112 hospitalised patients, most presented with cough (88%) and/or fever (82%), but several (4%) had neither symptom. A quarter of female patients (15) were pregnant or in the post-partum period. Patients presenting with multifocal changes on chest x-ray had significantly longer hospital lengths of stay, and were more likely to require intensive care unit admission. Thirty patients required admission to an intensive care unit, and three died during their acute illness. The median length of intensive care admission was 10.5 days (interquartile range, 5-16 days). Conclusion(s): This study highlights risk factors for severe disease, particularly pregnancy. Clinical and public health planning for upcoming influenza seasons should take into account the spectrum and severity of clinical infection demonstrated in this report, and the need to concentrate resources effectively in high-risk patient groups.

The grain N uptake response of an opportunity cropping regime comprising summer and winter cereal and legume crops to fertiliser nitrogen (N) and phosphorus (P) applications was studied in 2 long-term experiments with contrasting durations of cultivation. At the longer cultivation duration Colonsay site (>44 years at commencement), grain N uptake increased with fertiliser N application in 15 of 17 harvested crops from 1985 to 2003. Grain sorghum on short-fallow consistently responded to applied fertiliser N at higher rates (>= 80 kg N/ha) than crops grown on long-fallow where either fertiliser at nil or 40 kg N/ha maximised grain N uptake. Winter cereal response to applied N was influenced by fallow length, generally smaller responses in long fallow years, although in-crop rainfall affected this. Short-fallow crops responded up to 40 or 80 kg applied N/ha, while seasonal growing-season rainfall affected the responses of the double-crop winter cereals the most. Responses to applied fertiliser N at the shorter duration cultivation Myling site (9 years at commencement) generally occurred only under high-intensity cropping periods, or in those crops sown following periods of slower potential N mineralisation. Phosphorus fertiliser application influenced grain N uptake at both locations in some years, with winter cereals, legumes, and sorghum sown following long-fallow generally significant. Cumulative grain N uptakes in both experiments were independently influenced by fertiliser N and P treatments, P having an additive effect, increasing grain yield and grain N removed. Recovery efficiency of fertiliser N in grain, derived from cumulative N fertiliser application and grain N uptake, in general declined as amount of fertiliser N applied increased; however, as N supplies became less limiting to yield, P fertiliser generated higher fertiliser N recovery in grain. At Colonsay, RENG from cumulative uptake and removal was >= 0.48 with fertiliser P application for cumulative

This paper reports on the use of APSIM - Maize for retrospective analysis of performance of a high input, high yielding maize crop and analysis of predicted performance of maize grown with high inputs over the long-term (>100 years) for specified scenarios of environmental conditions (temperature and radiation) and agronomic inputs (sowing date, plant population, nitrogen fertiliser and irrigation) at Boort, Victoria, Australia. It uses a high yielding (17 400 kg/ha dry grain, 20 500 kg/ha at 15% water) commercial crop grown in 2004-05 as the basis of the study. Yield for the agronomic and environmental conditions of 2004-05 was predicted accurately, giving confidence that the model could be used for the detailed analyses undertaken. The analysis showed that the yield achieved was close to that possible with the conditions and agronomic inputs of 2004-05. Sowing dates during 21 September to 26 October had little effect on predicted yield, except when combined with reduced temperature. Single year and long-term analyses concluded that a higher plant population (11 plants/m2) is needed to optimise yield, but that slightly lower N and irrigation inputs are appropriate for the plant population used commercially (8.4 plants/m2). Also, compared with changes in agronomic inputs increases in temperature and/or radiation had relatively minor effects, except that reduced temperature reduces predicted yield substantially. This study provides an approach for the use of models for both retrospective analysis of crop performance and assessment of long-term variability of crop yield under a wide range of agronomic and environmental conditions.

Two field experiments using maize (Pioneer 31H50) and three watering regimes [(i) irrigated for the whole crop cycle, until anthesis, (ii) not at all (experiment 1) and (iii) fully irrigated and rain grown for the whole crop cycle (experiment 2)] were conducted at Gatton, Australia, during the 2003-04 season. Data on crop ontogeny, leaf, sheath and internode lengths and leaf width, and senescence were collected at 1- to 3-day intervals. A glasshouse experiment during 2003 quantified the responses of leaf shape and leaf presentation to various levels of water stress. Data from experiment 1 were used to modify and parameterise an architectural model of maize (ADEL-Maize) to incorporate the impact of water stress on maize canopy characteristics. The modified model produced accurate fitted values for experiment 1 for final leaf area and plant height, but values during development for leaf area were lower than observed data. Crop duration was reasonably well fitted and differences between the fully irrigated and rain-grown crops were accurately predicted. Final representations of maize crop canopies were realistic. Possible explanations for low values of leaf area are provided. The model requires further development using data from the glasshouse study and before being validated using data from experiment 2 and other independent data. It will then be used to extend functionality in architectural models of maize. With further research and development, the model should be particularly useful in examining the response of maize production to water stress including improved prediction of total biomass and grain yield. This will facilitate improved simulation of plant growth and development processes allowing investigation of genotype by environment interactions under conditions of suboptimal water supply.

OBJECTIVES. The purpose of this work was to assess the impact of recently described human metapneumovirus and human coronavirus NL63 compared with other respiratory viruses by using sensitive molecular techniques in a cohort of healthy preschool-aged children. We also aimed to assess the use of parent collection to obtain an adequate respiratory specimen from acutely unwell children in the community. PATIENTS AND METHODS. The community epidemiology and burden of human metapneumovirus and other respiratory viruses (influenza A, influenza B, respiratory syncytial virus, parainfluenza viruses, adenoviruses, and picornaviruses) were examined in a cohort of 234 preschool-aged children from Melbourne, Australia, over a 12-month period by using polymerase chain reaction testing. Parents collected a daily symptom diary for the duration of the study and were taught to collect a combined nose-throat swab and complete an impact diary when the study child had an acute respiratory illness. RESULTS. The average incidence of acute respiratory illness was 0.48 per child-month for the duration of the study, with a winter peak. Of 543 illnesses with >=1 specimen returned, 33 were positive for human metapneumovirus (6.1%) and 18 for human coronavirus NL63 (3.3%). Of all of the viruses for which we tested, human metapneumovirus and human coronavirus NL63 were most strongly linked to child care attendance, occurring in 82% and 78% of infected children, respectively. Picornaviruses were the most commonly identified virus group (269 [49.5%]). Influenza virus and adenovirus illnesses had the greatest impact, with fever in more than three quarters and requiring, on average, >1 local doctor visit per illness. CONCLUSIONS. Recently identified human metapneumovirus and human coronavirus NL63 are important pathogens in community-based illness in children, particularly in those who attend child care. Picornaviruses were detected in half of the nose-throat swabs collected during acute respiratory

This paper reports on a purposive survey study which aimed to identify needs for the development, delivery and evaluation of applied climate education for targeted groups, to improve knowledge and skills to better manage under variable climatic conditions. The survey sample consisted of 80 producers and other industry stakeholders in Australia (including representatives from consulting, agricultural extension and agricultural education sectors), with a 58% response rate to the survey. The survey included an assessment of (i) knowledge levels of the Southern Oscillation Index and sea surface temperatures, and (ii) skill and ability in interpreting weather and climate parameters. Results showed that despite many of the respondents having more than 20 years experience in their industry, the only formal climate education or training undertaken by most was a 1-day workshop. Over 80% of the applied climate skills listed in the survey were regarded by respondents as essential or important, but only 42% of educators, 30% of consultants and 28% of producers rated themselves as competent in applying such skills. Essential skills were deemed as those that would enable respondents or their clients to be better prepared for the next extended wet or dry meteorological event, and improved capability in identifying and capitalising on key decision points from climate information and a seasonal climate outlook. The complex issue of forecast accuracy is a confounding obstacle for many in the application of climate information and forecasts in management. Addressing this problem by describing forecast 'limitations and skill' can help to overcome this problem. The survey also highlighted specific climatic tactical and strategic information collated from grazing, cropping and agribusiness enterprises, and showed the value of such information from a users perspective.

Reliability of supply of feed grain has become a high priority issue for industry in the northern region. Expansion by major intensive livestock and industrial users of grain, combined with high inter-annual variability in seasonal conditions, has generated concern in the industry about reliability of supply. This paper reports on a modelling study undertaken to analyse the reliability of supply of feed grain in the northern region. Feed grain demand was calculated for major industries (cattle feedlots, pigs, poultry, dairy) based on their current size and rate of grain usage. Current demand was estimated to be 2.8Mt. With the development of new industrial users (ethanol) and by projecting the current growth rate of the various intensive livestock industries, it was estimated that demand would grow to 3.6Mt in three years time. Feed grain supply was estimated using shire scale yield prediction models for wheat and sorghum that had been calibrated against recent ABS production data. Other crops that contribute to a lesser extent to the total feed grain pool (barley, maize) were included by considering their production relative to the major winter and summer grains, with estimates based on available production records. This modelling approach allowed simulation of a 101-year time series of yield that showed the extent of the impact of inter-annual climate variability on yield levels. Production estimates were developed from this yield time series by including planted crop area. Area planted data were obtained from ABS and ABARE records. Total production amounts were adjusted to allow for any export and end uses that were not feed grain (flour, malt etc). The median feed grain supply for an average area planted was about 3.1Mt, but this varied greatly from year to year depending on seasonal conditions and area planted. These estimates indicated that supply would not meet current demand in about 30% of years if a median area crop were planted. Two thirds of the years wi

The ability to predict accurately dry matter (DM) accumulation, partitioning, and thus final grain yield is crucial in crop simulation models. The objectives of the study were to measure radiation interception and radiation use efficiency, to quantify the distribution of DM among the various plant parts, and to develop improved methods of modelling DM accumulation and partitioning among plant parts. Five cultivars of maize differing widely in maturity and adaptation were planted in October 1993 in south- eastern Queensland, and grown under non-limiting conditions of water and plant nutrient supplies. Data on DM accumulation, light interception, and canopy development were collected. The light extinction coefficient (k) did not differ among the cultivars. Radiation use efficiency was constant in each cultivar until close to physiological maturity, when a small decline was observed. Partitioning of DM between leaves and stems (until 90% of leaf tips had appeared) was described by a linear relationship between the proportion of DM allocated to leaves and the number of leaves present. Ear growth was described by a thermal-time-dependent equation from 150 degree-days (base temperature 8˚C) before silking to 115 degree-days after silking. Predictions of accumulation of grain yield by either components of yield (grain number per plant and individual grain weight) or daily increase in harvest index were assessed, but neither was entirely satisfactory, the former because of inaccurate prediction of grain number per plant, and the latter because of differences among cultivars in the daily increase in harvest index and terminal harvest index. Thus, the use of genotype-specific coefficients remains necessary. Throughout crop life, DM in stems can be predicted by difference, once DM is allocated to other plant parts. The relationships presented where leaf number mediates DM partitioning before silking simplify modelling of DM accumulation and partitioning in maize.

Prediction of phenological development is crucial to the successful use of crop simulation in crop adaptation studies. Previous studies have shown existing predictive algorithms to be inadequate when applied to a broad range of cultivars and environments. The primary objective of the study was to quantify the temperature and photoperiod responses of the rates of development during emergence to tassel initiation (ETI) for a diverse set of maize cultivars. Five cultivars of maize, differing in maturity and adaptation, were sown on seven dates from 1 October 1993 to 29 March 1994 and grown under natural and extended (16.5 h) photoperiods at Gatton, Southeast Queensland, under non-limiting conditions of water and plant nutrient supplies. Timing of emergence and tassel initiation were observed for all treatments. The base, optimum, and maximum temperatures, and photoperiod sensitivity of each cultivar were determined using an iterative optimisation procedure. The critical photoperiod (12.5 h) was adopted from literature sources, as there was inadequate range in the short photoperiods in the present study to determine it with confidence. Photoperiod extension increased the duration of ETI and increased the number of leaves on all cultivars, the largest increases occurring in a tropically adapted cultivar (Barker), in five of the seven sowings. No response to photoperiod extension occurred in the crops sown on 24th February and 29th March 1994. The temperature response was the same in all cultivars, and was best described by a three-stage broken-stick linear function. Photoperiod sensitivity was linear at photoperiods in excess of 12.5 h. The optimised base, optimum and maximum temperatures were 8, 34 and 40°C respectively. Photoperiod sensitivity, expressed as the increase in number of leaves produced per hour of photoperiod in excess of 12.5 h, ranged from 0.3 to 1.5 leaves h−1. When expressed as the increase in thermal duration of the photoperiod-sensitive interval prio

The ability to predict leaf area and leaf area index is crucial in crop simulation models that predict crop growth and yield. Previous studies have shown existing methods of predicting leaf area to be inadequate when applied to a broad range of cultivars with different numbers of leaves. The objectives of the study were to (i) develop generalised methods of modelling individual and total plant leaf area, and leaf senescence, that do not require constants that are specific to environments and/or genotypes, (ii) re-examine the base, optimum, and maximum temperatures for calculation of thermal time for leaf senescence, and (iii) assess the method of calculation of individual leaf area from leaf length and leaf width in experimental work. Five cultivars of maize differing widely in maturity and adaptation were planted in October 1994 in south-eastern Queensland, and grown under non-limiting conditions of water and plant nutrient supplies. Additional data for maize plants with low total leaf number (12-17) grown at Katumani Research Centre, Kenya, were included to extend the range in the total leaf number per plant. The equation for the modified (slightly skewed) bell curve could be generalised for modelling individual leaf area, as all coefficients in it were related to total leaf number. Use of coefficients for individual genotypes can be avoided, and individual and total plant leaf area can be calculated from total leaf number. A single, logistic equation, relying on maximum plant leaf area and thermal time from emergence, was developed to predict leaf senescence. The base, optimum, and maximum temperatures for calculation of thermal time for leaf senescence were 8, 34, and 40ºC, and apply for the whole crop-cycle when used in modelling of leaf senescence. Thus, the modelling of leaf production and senescence is simplified, improved, and generalised. Consequently, the modelling of leaf area index (LAI) and variables that rely on LAI will be improved. For experimental

Prediction of the initiation, appearance and emergence of leaves is critically important to the success of simulation models of crop canopy development and some aspects of crop ontogeny. Data on leaf number and crop ontogeny were collected on five cultivars of maize differing widely in maturity and genetic background grown under natural and extended photoperiods, and planted on seven sowing dates from October 1993 to March 1994 at Gatton, South-east Queensland. The same temperature coefficients were established for crop ontogeny before silking, and the rates of leaf initiation, leaf tip appearance and full leaf expansion, the base, optimum and maximum temperatures for each being 8, 34 and 40 degrees C. After silking, the base temperature for ontogeny was 0 degrees C, but the optimum and maximum temperatures remained unchanged. The rates of leaf initiation, appearance of leaf tips and full leaf expansion varied in a relatively narrow range across sowing times and photoperiod treatments, with average values of 0.040 leaves (degrees Cd)-1, 0.021 leaves (degrees Cd)-1, and 0.019 leaves (degrees Cd)-1, respectively. The relationships developed in this study provided satisfactory predictions of leaf number and crop ontogeny (tassel initiation to silking, emergence to silking and silking to physiological maturity) when assessed using independent data from Gatton (South eastern Queensland), Katherine and Douglas Daly (Northern Territory), Walkamin (North Queensland) and Kununurra (Western Australia).

Mean protein concentrations in wheat (Triticum aestivum) on the Darling Downs of southern Queensland have fallen below 10% in recent years, preventing farmers from obtaining 'Prime Hard' status (13.0%) for their wheat crop. Two management options, for improving this situation are applications of nitrogenous fertiliser in a wheat monoculture or inclusion of a legume in rotation with wheat. Long-term trials at Warra, on the western Darling Downs, resulted in the selection of chickpea (Cicer arietinum) as a useful grain legume cash crop with potential for improvement of its nitrogen (N) fixing ability through management. This 2-year study examined the effect of sowing time and tillage practice on dry matter yield, grain yield, N accumulation and N2 fixation in chickpea and the subsequent soil N balance. There were 3 sowing times during autumn and winter of each year using conventional tillage (CT). Zero tillage (ZT) was introduced after the first crop for all sowing times. Greater total dry matter yield and grain yield (4.18-5.95 and 1.63-2.25 t/ha, respectively) resulted from sowing in autumn or early winter than from sowing in late winter (3.39-3.86 and 0.97-1.22 kg/ha, respectively). The effects of tillage practice were variable, depending on growth stage. At harvest, ZT plots produced greater total dry matter yield (4.20 t/ha) and grain yield (1.94 t/ha) than CT plots (3.01 and 1.29 t/ha, respectively), whereas at the time of maximum dry matter, yield was higher under CT for autumn sowings, and under ZT for winter sowings.

Following long-term studies at Warra, on the western Darling Downs, chckpea (Cicer anetinum) was selected as a useful grain legume cash crop with potential for improvement of its nitrogen (N) fixing ability through management. This 2-year study examined the effect of sowing time and tillage practice on dry matter yield, grain yield (Horn et al. 1996), N accumulation, N2 fixation, and the subsequent soil N balance. Generally, greater N accumulation resulted from sowing in late autumn-early winter (89-117 kg N/ha) than sowing in late winter (76-90 kg N/ha). The amount of N2 fixed was low in both years (15-32 kg N/ha), and was not significantly affected by sowing time or tillage. The potential for N2 fixation was reduced in both years due to high initial soil nitrate levels and low total biomass of chickpea because of low rainfall. Nitrogen accumulation by grain was higher under zero tillage (ZT) than conventional tillage (CT) for all sowing times, and this affected the level of grain N export. The consequence of low N2 fixation and high N export in chickpea grain was a net loss of total soil N, (2-48 kg N/ha under CT and 22-59 kg N/ha under ZT). Management practices to ensure larger biomass production and lower soil nitrate-N levels may result in increased N2 fixation by chickpea and thus a positive soil N balance.