基于MODIS的河西走廊高平原荒漠草原区生产力遥感模型研究

采用2008年河西走廊高平原荒漠草原区地面监测数据,结合MODIS数据生成的evi、ndvi、rvi、osavi、tvi、msavi、dvi等7种植被指数,分别建立一次函数、对数、幂、指数、二次多项式等5种模型,共建立35个估产模型,比较每个模型的决定系数,选出rvi建立的对数模型为最佳模型。运用2007年、2009年的地面产草量数据对估产模型进行验证,估产精度均在75%以上。因此,利用rvi建立的对数模型最能反映实际的地上生物量,具有跨年度利用的实际价值。     

草原产草量遥感估算方法发展趋势及影响因素

草原产草量估算是实行以草定畜、草畜平衡管理的前提条件。遥感模型方法是目前从宏观上用于估算产草量的有效方法。该研究对遥感估算方法进行了详细阐述,并针对国内外的研究现状,分别讨论了基于遥感的统计模型法、综合模型法和其它相关方法,分析了不同方法的优缺点,探讨了建模过程中的影响因素,最后对产草量遥感估算方法的发展趋势及前景进行了展望。遥感模型法中的统计模型仍是今后大面积估产中应用的重点,而遥感模型法中的综合模型在今后草地生物量估算中将有很大的发展潜力,新的数学方法的不断探索和多种相关模型的不断融合将实现从微观形成机制的研究到宏观产量形成模拟的一体化方面有着重要的前景。     

The Evidentiary Value of Challenge Trials for Three Pre‐harvest Food Safety Topics: A Systematic Assessment

Reducing zoonotic pathogens in food animals prior to harvest will reduce the pathogen burden that enters the food chain and the environment. Consequently, the burden of enteric illness in humans may be reduced. Evaluating interventions to reduce a pathogen in animals often begins with challenge trials, in which animals are deliberately exposed to the pathogen under controlled conditions. Challenge trials are subsequently followed by field trials, also known as randomized controlled trials, in which the animals are naturally exposed to the pathogen. Challenge trials can most effectively inform field trials only if they precede field trials, are robust, internally valid and transparently reported. Using systematic review and meta‐analysis methodology, we examined the pre‐harvest food safety literature for three intervention—pathogen—species combinations: probiotics/competitive exclusion products in ruminants to reduce Escherichia coli O157 shedding, vaccines in ruminants to reduce E. coli O157 shedding and vaccines in swine to reduce Salmonella shedding. We examined two outcomes, prevalence of faecal shedding at the end of the trial and prevalence of faecal shedding throughout the trial period, to compare challenge trials and field trials. We found that challenge trials occurred concurrently with field trials, challenge trials suffered from reporting deficiencies of methodological features, challenge trials tended to report a more favourable outcome than field trials, and there was some evidence of publication bias among all three intervention–pathogen–species combinations. Challenge trials would better serve to inform field trials if they precede field trials, are methodologically sound, include transparent reporting and are published regardless of their results. In addition, due to our findings of greater efficacy reported among challenge trials compared with field trials, risk models predicting the public health benefits of pre‐harvest interventions to reduce zoonotic pathogens in livestock might be best served by field trial results alone.     

Baiting intervals and duration of control of the small fox tapeworm: a simulation study

Field trials to control the small fox tapeworm Echinococcus multilocularis failed to reduce the prevalence of the parasite persistently. With the experience from this empirical work, a simulation model for the population dynamics of the small fox tapeworm was developed. This model is used to examine the effect of different control strategies. Sufficient control duration is able to eradicate the parasite in simulation experiments. Baiting intervals of 4 or 6 weeks were found to be more efficient than shorter or longer intervals. The strategy used in field trials showed no sustainable effect in any of the simulation experiments. The applicability of simulation models for the planning of control measures for wildlife diseases is discussed.     

Design of field trials for the evaluation of antibacterial products for therapy of bovine clinical mastitis

In this paper, the design and statistical analysis of field trials for the evaluation of the efficacy of clinical mastitis therapeutics is covered. First, general issues underlying the design of clinical trials are reviewed. These include bias and confounding; randomization and blocking; and study objectives and choice of the corresponding hypothesis. Specific issues in the design of clinical mastitis trials are also discussed. Selection of subjects is discussed with regard to choice of experimental units, identification of reference population and study population, inclusion and exclusion criteria, and sample size calculation. Next, a section on treatment administration and evaluation of cure reviews treatment, blinding, choice of response measure, as well as compliance, withdrawal, and early termination. The statistical analysis section addresses possible statistical models, treatment of confounding, and fixed vs. random effects. In conclusion, well-conducted clinical mastitis trials represent an invaluable, albeit difficult and expensive, effort to evaluate efficacy and tolerance under usual circumstances of use.     

Review of mathematical models for sow herd management

This paper is a survey of the different sow models described in literature, which made use of different mathematical methodologies, and were intended for sow herd management. Models were discussed under a wide classification, that is, simulation and optimisation. The latter included linear programming and dynamic programming with Markov decision models and optimal control as major representative models. In a first stage we recalled general traits and modelling foundations of herd management models and later, different aspects of sow herd models published up to now were reviewed. Special attention is paid to main variables, source of parameters, validation, output and intended use. Most of such models have been developed as research tools and teaching aids. Actually, the increasing ability to represent complex systems is not corresponded with an augmentation of decision support tools including such complex models in field conditions. Thus, a need of new proposals dealing with transient situations and non-time homogeneous parameters was detected. The inclusion of variability-risk features and multicriteria decision methods was also of interest for practical purposes. Actual changes in the pig sector lead to expect new management herd models, in particular considering more than one herd at a time.     

Oral immunisation of wild boar against classical swine fever: concluding analysis of the recent field trials in Germany

The recent oral immunisation trials in wild boar against classical swine fever (CSF) in Germany are described and evaluated in summary. After the first field study in Lower Saxony from 1993-1995 further immunisation trials started in Mecklenburg-Western Pomerania, Brandenburg, Lower Saxony, Baden-Württemberg and Saxony-Anhalt. The immunisation strategies and the size of the vaccination zones were different in the individual federal states. In principle, the bait vaccine based on the CSF virus strain "C" were laid out by hand. Later also the aerial distribution was carried out in selected areas of Mecklenburg-Western Pomerania. The application of baits by plane was introduced at the beginning of the immunisation measures in Saxony-Anhalt apart from the manual distribution. Up to now, the field trials show that the oral immunisation can be an additional tool for CSF control by increasing of herd immunity and reduction of the CSFV prevalence. However, the immunisation was not sufficient enough for young boars in the most field studies. Based on the evaluation of the immunisation experiments an improved immunisation procedure is recommended.     

Long-lasting prevention against blowfly strike using the insect growth regulator dicyclanil

OBJECTIVE: To assess a ready-to-use formulation of dicyclanil to prevent blowfly strike on Merino sheep under Australian conditions. DESIGN: Randomised clinical trials conducted in an environment house and in the field. PROCEDURE: Two environment house trials were used to measure the protection against flystrike provide by a jetting or a ready-to-use 5% spray-on formulation of dicyclanil over 22 and 31 weeks respectively. Oviposition and strikes were recorded weekly for each sheep. In two field trials the occurrence of strike in Merino sheep treated off-shears or in long wool with dicyclanil or with cyromazine was compared for up to 38 weeks after treatment. Efficacy was assessed by calculating the cumulative percentage of sheep struck. RESULTS: Under environment house conditions, sheep jetted with dicyclanil at 1.50, 0.75 and 0.30 g per sheep developed 0, 8 and 9 strikes respectively during the 22 weeks of the trial, whereas there were 358 strikes present in the placebo group. Sheep sprayed with dicyclanil at 2.25, 1.50 and 0.75 g per sheep developed 5, 11 and 29 strikes respectively between weeks 15 and 31 after treatment, whereas there were 185 strikes present in the untreated controls. In field trials the cumulative percentage of sheep struck reached 1% between weeks 12 to 13 after sheep had been treated with cyromazine. Sheep treated with dicyclanil reached the 1% limit at week 21 after treatment. CONCLUSION: Under Australian field conditions, a ready-to-use 5% spray-on formulation of dicyclanil applied off-shears or to long wool protected Merino sheep from blowfly strike for a period of at least 20 weeks.     

Parasitic contamination cycles and mathematical epidemiology

Summary

Mathematics plays an essential role in epidemiology. Whether simple questions are asked about simple relations, or complicated questions about complicated relations, the best fitting mathematical figures are always searched for. In a holistic approach, it may often be necessary to assess complicated relations by using (real) mathematical models (simulation models). Examples are presented of parasitic contamination cycles which require more or less complicated mathematics to answer epidemiological questions regarding prevalence and incidence of infection in the human population: Trichinella, Toxocara and Toxoplasma. Some general remarks on epidemiological insights which are necessary to understand abstract concepts of the ‘real world’ (mathematical modelling), are discussed.     

Attenutated live fowl cholera vaccine. III. Laboratory and field vaccination trials in turkeys and chickens

Administered via the drinking water, M-3-G, an attenuated strain of Pasteurella multocida of serotype 1, was found to immunize turkeys and chickens against fowl cholera. Immunity was tested by challenging birds intramuscularly, by palatine cleft swab, or orally after 3 vaccinations. No reactions to vaccination were noted in 390 turkeys in 12 laboratory trials, nor in 20,245 vaccinated in field trials. Chickens showed no vaccination reactions, and immunity was elicited by challenge in a laboratory trial and in face of natural outbreaks in the field, where 11,600 chickens were vaccinated. No vaccination reactions were noted, although most birds involved in the trials were carrying Mycoplasma spp. Immunity was found to last about 10 weeks after the last vaccination. The immunizing properties of M-3-G are compared with the CU strain.     

Vaccinating against zoonotic parasitic diseases: myth or reality?

The largely unanticipated difficulties of parasite vaccine development have led us to a renewed awareness of the survival strategies evolutionarily embedded within parasites over hundreds of millions of years. We have grown to appreciate that efforts to disrupt parasite-host relationships are substantially compounded by our incomplete understanding of the complex immune responses that occur in the naturally infected host. Given the inability to transfer laboratory successes to field trials, research is leading us to conclude that genetically defined animal models may not be good predictors of the unique and disparate protective immune responses one can expect from the genetically heterogeneous populations of animals that represent the parasite's natural environment. This is further compounded by the abundance of mechanisms parasites have created for themselves to defend against immune intervention. Thus, in the never-ending saga of vaccine development, it is only appropriate that pitfalls and advancements be critiqued as they apply across parasite groups, with a look towards promising technologies that may propel this field to the level of scientific achievement once envisaged.     

Modeling of host genetics and resistance to infectious diseases: understanding and controlling nematode infections

This paper considers approaches to modeling the dynamics of infectious disease and the application of such models to nematode parasite infections in ruminants. Particularly, these models are developed to account for host genetics and may be used to assess the effects of using genetics to control nematode infections. Three main issues are critically examined: the infection transmission cycle from pasture to host to pasture, the expected genetic relationships between resistance and performance, and the risks of parasite evolution in response to genetic changes in the host. To obtain answers that are realistic and of practical use, the modeling approaches require a solid grounding in biology. This biology is formalized and described using mathematical techniques, with the models parameterized using experimental or field data. Transmission dynamics have been quantified by modeling and are backed by strong experimental data. Selection for resistance will be successful in reducing egg output, pasture larval contamination and hence subsequent larval challenge. Modeling frameworks have been developed to predict genetic relationships between resistance to infectious disease and performance in general, and genetic correlations predicted for nematode resistance are close to mean published values. These predicted correlations strengthen as the larval challenge increases and the dietary (protein) adequacy decreases, however modeling challenges remain. Lastly, although convincing experimental data is not yet available, arguments based on modeling suggest that the risks of parasite evolution in response to genetic changes in the host should be less than the risks arising from other control strategies, such as anthelmintics. Thus, modeling techniques predict that selective breeding for resistance should be an effective and sustainable complementary control measure.     

Evaluation of spinosad for the oral treatment and control of flea infestations on dogs in Europe

The novel ectoparasiticide spinosad is a naturally occurring mixture of spinosyns A and D formed during a fermentation process. The spinosyns are tetracyclic macrolides with a unique ring system. Their mode of action differs from that of other commercially available insecticides. Laboratory and field trials were conducted to evaluate the use of spinosad in a chewable tablet at a dose range of 45 to 70 mg/kg for the treatment and control of flea infestations on dogs in Europe. Laboratory studies with artificially infested dogs confirmed persistent activity against Ctenocephalides felis of higher than 99 per cent at three weeks post-treatment with values of 96.5 to 97.8 per cent at four weeks. Two multicentric field trials with naturally infected client-owned animals in five European countries used selamectin as comparator. Monthly doses were given during the summer when many homes were heavily infested. Households with spinosad-treated dogs showed cumulative benefits with flea burdens reduced by about 97 per cent at 14 and 30 days and by 99.6 per cent at 60 and 90 days. Corresponding figures for selamectin were significantly lower (P<0.05) at all time points: between 88.5 and 91 per cent at 14 and 30 days, then 97.8 and 98.2 per cent at 60 and 90 days. Thus, the performance of spinosad compared favourably with that of the established reference product.     

Field trials evaluating ivermectin controlled-release capsules for weaner sheep and for breeding ewes

Objective To confirm the efficacy of ivermectin released from a controlled-release capsule administered to young sheep and to breeding ewes under field conditions. Design Randomised field trials. Procedure In each of ten field trials 25 weaned lambs were treated with ivermectin controlled-release capsules and 25 remained untreated. Eight similar field trials were conducted using adult ewes. Efficacy against infections of gastrointestinal nematodes was assessed by faecal egg counts and faecal larval culture. Body weights were recorded and faecal soiling of the breech wool (dags) was assessed. Results Nematode faecal egg counts in the two groups were not different (P = 0.13) before treatment in the weaner trials or before treatment in the ewe trials (P = 0.49), but thereafter eggs in the untreated sheep persisted, whereas counts in sheep given capsules were negligible (P ≤ 0.01). In the weaner trials, dag scores for the two groups were not different at the start of the trials (P = 0.18) but at the end, untreated sheep had significantly more dags (P = 0.04) than treated sheep. In the ewe trials, dag scores remained low in both groups. Weaners treated with the capsule gained 1.4 kg (95% CL: 0.7, 3.1) more weight over the 16 week trial period compared to untreated weaners (P = 0.01). Both groups of ewes lost weight as a result of parturition but the mean loss by week 16 was greater for untreated (3.7 kg) (95% CL: -5.1,-2.2) than for treated ewes (1.8 kg) (95% CL: -3.3, -0.4). The mean change in ewe body weight for the two groups was however not significant (P = 0.07). Differentiation of nematode larvae recovered from cultures of faeces from untreated animals indicated that the capsules were effective against the common parasites of sheep. Conclusion The capsule was efficacious against gastrointestinal nematodes judging from faecal egg counts. It has the potential to significantly reduce contamination of pasture with nematode eggs. Treated weaners had less dags for 16 weeks and gained more weight than untreated weaners.     

Automated detection of estrus and mastitis in dairy cows

The development and test of detection models for oestrus and mastitis in dairy cows is described in a PhD thesis that was defended in Wageningen on June 5, 2000. These models were based on sensors for milk yield, milk temperature, electrical conductivity of milk, and cow activity and concentrate intake, and on combined processing of the sensor data. The models alert farmers to cows that need attention, because of possible oestrus or mastitis. A first detection model for cows, milked twice a day, was based on time series models for the sensor variables. A time series model describes the dependence between successive observations. The parameters of the time series models were fitted on-line for each cow after each milking by means of a Kalman filter, a mathematical method to estimate the state of a system on-line. The Kalman filter gives the best estimate of the current state of a system based on all preceding observations. This model was tested for 2 years on two experimental farms, and under field conditions on four farms over several years. A second detection model, for cow milked in an automatic milking system (AMS), was based on a generalization of the first model. Two data sets (one small, one large) were used for testing. The results for oestrus detection were good for both models. The results for mastitis detection were varying (in some cases good, in other cases moderate). Fuzzy logic was used to classify mastitis and oestrus alerts with both detection models, to reduce the number of false positive alerts. Fuzzy logic makes approximate reasoning possible, where statements can be partly true or false. Input for the fuzzy logic model were alerts from the detection models and additional information. The number of false positive alerts decreased considerably, while the number of detected cases remained at the same level. These models make automated detection possible in practice.     

Mathematical description of the concentration of Oxytetracycline and penicillin-G in tissue cages in calves as related to the serum concentration

A mathematical model based on Fick's laws of diffusion describing the concentration of drug in tissue cage models was elaborated. The model takes into account differences in protein binding, tissue cage geometry and serum pharmacokinetics. The validity of the model was tested against experimental data obtained from a tissue cage model in calves by simultaneous fitting to serum and tissue cage fluid (TCF) data in a non-linear least-squares regression computer program. Concentrations of penicillin-G (pen-G) in serum and TCF following intravenous (i.v.) administration of potassium pen-G were adequately described by the mathematical model. Concentrations in TCF after intramuscular (i.m.) administration of the same drug and of procaine pen-G could be predicted by the mathematical model. Concentrations of oxytetracycline (OTC) in serum and TCF following i.v. administration and continuous i.v. infusions were also adequately described by the model, and TCF concentrations after i.m. administration of the same drug could be roughly predicted. The results indicate that pen-G and OTC have the same permeability coefficient for transport from serum to TCF.     

Quality of Reporting of Clinical Trials of Dogs and Cats and Associations with Treatment Effects

Background: To address concerns about the quality of reporting of randomized controlled trials, and the potential for biased treatment effects in poorly reported trials, medical journals have adopted a common set of reporting guidelines, the Consolidated Standards of Reporting Trials (CONSORT) statement, to improve the reporting of randomized controlled trials.
Hypothesis: The reporting of clinical trials involving dogs and cats might not be ideal, and this might be associated with biased treatment effects.
Animals: Dogs and cats used in 100 randomly selected reports of clinical trials.
Methods: Data related to methodological quality and completeness of reporting were extracted from each trial. Associations between reporting of trial features and the proportion of positive treatment effects within trials were evaluated by generalized linear models.
Results: There were substantive deficiencies in reporting of key trial features. An increased proportion of positive treatment effects within a trial was associated with not reporting: the method used to generate the random allocation sequence ( P < .001), the use of double blinding ( P < .001), the inclusion criteria for study subjects ( P = .003), baseline differences between treatment groups ( P = .006), the measurement used for all outcomes ( P = .002), and possible study limitations ( P = .03).
Conclusions and Clinical Importance: Many clinical trials involving dogs and cats in the literature do not report details related to methodological quality and aspects necessary to evaluate external validity. There is some evidence that these deficiencies are associated with treatment effects. There is a need to improve reporting of clinical trials, and guidelines, such as the CONSORT statement, can provide a valuable tool for meeting this need.     

The serological responses of chickens to mass vaccination with a live V4 Newcastle disease virus vaccine in the field and in the laboratory 1. Meat chickens

Meat chickens on commercial broiler farms were vaccinated once at 1 to 15 days of age with a live V4 Newcastle disease virus (NDV) vaccine administered by drinking water, aerosol or coarse spray. Hatchmates were housed and similarly vaccinated in laboratory isolation pens. Samples of birds were bled at weekly to fortnightly intervals and the serums tested for haemagglutination inhibiting antibody to NDV. Log2 mean titres of up to 6.26, and assumed protection levels (based on the percentage of birds with log2 titres of 4 or greater) of up to 89%, were obtained in field trials within 4 weeks of vaccination. Differences were observed between the results obtained from parallel field and laboratory trials. The presence of maternal NDV antibody reduced the response to vaccination. The results show that this V4 vaccine can produce an adequate serological response following mass administration to Australian meat chickens housed under commercial conditions.     

Parasitic contamination cycles and mathematical epidemiology

Mathematics plays an essential role in epidemiology. Whether simple questions are asked about simple relations, or complicated questions about complicated relations, the best fitting mathematical figures are always searched for. In a holistic approach, it may often be necessary to assess complicated relations by using (real) mathematical models (simulation models). Examples are presented of parasitic contamination cycles which require more or less complicated mathematics to answer epidemiological questions regarding prevalence and incidence of infection in the human population: Trichinella, Toxocara and Toxoplasma. Some general remarks on epidemiological insights which are necessary to understand abstract concepts of the 'real world' ('mathematical modelling'), are discussed.     

用数学预测模型改进传统实验研究方法—对旋毛虫成虫寄生寿命的研究

通常对旋毛虫成虫在小鼠体内存活期的测试是通过对人工感染小鼠的定期解剖而取得。本文介绍了灰色ＧＭ（１,２）模型的数学方法。对部分实验数据（２２天）建立ＧＭ（１,２）模型,预测结果与国内外经典著作报道相符。数学预测方法可以减少１２天工作量和节约３０只近交系小鼠。其作用是改进了传统的实验研究方法和提高了科研效率