Salmonella isolated from feeds and feed ingredients during the period 1982-1988: animal and public health implications

The prevalence of Salmonella in southern Africa in farm feeds and by-products of animal origin during 1982-1988 was determined. Salmonella occurred in 5.18% of the farm feed samples and in 9.54% of the by-product samples. Different serovars were isolated, some only once. The findings underestimate the true prevalence of Salmonella in farm feeds and by-products, and is representative of only the most severely contaminated products. The epidemiology of salmonellosis is discussed with special reference to the importance of multiple resistance to antibiotics, the increase in the number of cases of salmonellosis worldwide and "Salmonella free" feeds and foods. More detailed research on the role of farm feeds in the epidemiology of salmonellosis is required. Efforts should be made to increase awareness of the problem, to improve quality management at farm feed production plants and to develop efficient systems to monitor the hygienic safety of feeds and foods.     

Egg transmission of egg drop syndrome 1976 virus in fowl

Summary Egg transmission of egg drop syndrome 1976 virus (BC14 virus) in fowl was demonstrated in the second and third week after experimental infection. Eggs of BC14 virus infected hens were incubated weekly after disinfection with formaline gas. After 18 days of incubation, eggs with live embryos were homogenized. This egg material was fed to adult hens, housed in isolators. Seroconversion in these birds demonstrated egg transmission. It is suggested that egg transmission occurs as a result of viremia.     

Prepenetration stages in infection of clematis by Phoma clematidina

A detailed study of conidial germination, germ-tube growth and the formation of infection structures in Phoma clematidina , the causal agent of clematis wilt, is described for two clematis varieties differing in disease resistance. On both the resistant and susceptible varieties, the fungus entered leaves and stems by direct penetration of the cuticle, often, but not always, following the formation of infection structures. More germ tubes per conidium were formed on the susceptible host, but these germ tubes were on average shorter than on the resistant host. Although germ tubes regularly entered the plant via trichomes, stomata were not found to be sites of entry. Following penetration of the cuticle of resistant plants, germ-tube growth was sometimes restricted to the subcuticular region, and halo formation occurred at the sites where penetration was attempted. Subcuticular growth and halo formation were not observed on susceptible plants. These observations may partly explain the resistance of small-flowered clematis varieties to P. clematidina .     

在不使用抗生素的肉鸡中发现了抗生素耐药性菌株

禁止在家禽饲料中添加抗生素对于减少对人类健康有潜在威胁的耐药性细菌几乎没有作用。来自美国的一个科研小组通过研究得出了以上惊人的结论。     

Evaluation of host and bacterial gene modulation during Lawsonia intracellularis infection in immunocompetent C57BL/6 mouse model

BackgroundProliferative enteritis caused by Lawsonia intracellularis undermines the economic stability of the swine industry worldwide. The development of cost-effective animal models to study the pathophysiology of the disease will help develop strategies to counter this bacterium.ObjectivesThis study focused on establishing a model of gastrointestinal (GI) infection of L. intracellularis in C57BL/6 mice to evaluate the disease progression and lesions of proliferative enteropathy (PE) in murine GI tissue.MethodsWe assessed the murine mucosal and cell-mediated immune responses generated in response to inoculation with L. intracellularis.ResultsThe mice developed characteristic lesions of the disease and shed L. intracellularis in the feces following oral inoculation with 5 × l0⁷ bacteria. An increase in L. intracellularis 16s rRNA and groEL copies in the intestine of infected mice indicated intestinal dissemination of the bacteria. The C57BL/6 mice appeared capable of modulating humoral and cell-mediated immune responses to L. intracellularis infection. Notably, the expression of genes for the vitamin B12 receptor and for secreted and membrane-bound mucins were downregulated in L. intracellularis -infected mice. Furthermore, L. intracellularis colonization of the mouse intestine was confirmed by the immunohistochemistry and western blot analyses.ConclusionsThis is the first study demonstrating the contributions of bacterial chaperonin and host nutrient genes to PE using an immunocompetent mouse model. This mouse infection model may serve as a platform from which to study L. intracellularis infection and develop potential vaccination and therapeutic strategies to treat PE.     

The utilisation of poison hoppers designed for grey squirrel (Sciurus carolinensis Gmelin) control

The grey squirrel is recognised as a pest species of economic importance but the justification of the view appears to be founded on local areas of severe damage. Despite evidence that damage may not be alleviated by squirrel population destruction, Warfarin poisoning was introduced as an alternative to trapping.The utilisation by wildlife of a poison hopper designed for grey squirrel control was investigated by automatic photography. Results confirmed that a number of species may feed from the grain presented via the hopper. However, the majority of the bait was removed during the hours of darkness when grey squirrels were not active. It is a conservative estimate that between 55 and 65% of the grain entered the environment via animals other than squirrels.In addition, the removalof bait by night visitors resulted in the accumulation of large quantities of bait at and around the entrance to the hopper tunnel. This increased accessibility to the potentially poisoned bait by animals other than squirrels.Until such time as evidence is produced to show these results as exceptional, it can only be concluded that fears expressed over the lack of specificity of this method of control are justified.     

Management of the Northern Chesapeake Bay American shad fishery

The Shad fisheries of the Chesapeake Bay in Maryland have been declining since an 1897 peak of 7860 × 10³kg. No periods of stability have been recorded. Data are presented to trace the decline not only as a function of specific areas within the Northern Chesapeake Bay but also in terms of environmental problems and recruitment overfishing.The problem is related to improving the commercial fishing yield. An estimation of a maximum effort of 200,000 man-hours is suggested if a stable yield is to be approached. Methods for obtaining this goal include alternating of closed fishing areas, adoption of rest days, enforcement of fisheries regulations and reduction of the number of metres of gill net used per fisherman.     

A GIS-based plant prediction model for wetland ecosystems

An existing non-spatial model for the prediction of response of wetland plant species on ecological factors has been transformed into a GIS-based prediction model which produces spatial output at the landscape scale. The input, spatial patterns of the ecological factors, were constructed with geostatistical spatial interpolation (kriging). With this GIS-based model the spatial patterns of presence and absence of 78 wetland plant species are predicted for an area with wetlands in the Netherlands of approximately 500 square kilometers. The GIS-based model has been validated, and the estimated uncertainty of the input has been propagated through the model. At the species level the output shows spatially coherent and non-random patterns. The validation is affected by the propagation of input errors through the model. The number of valid predictions declines approximately 10–20% when 95% confidence intervals are used in the validation. This study shows that it is feasible to use a geostatistical interpolation method to construct spatial patterns of ecological factors on a landscape scale and to use these patterns as input for a GIS-based prediction model. The added uncertainty on the input values however, affects the number of valid predictions of the model.