Parasite problems in organic livestock and options for control

ABSTRACT: Organic livestock production has increased dramatically in recent years in Europe and other parts of the world. The aim of producing livestock under more natural conditions has led to a reversion to primarily outdoor production systems and less intensive housing when indoor, more forage-based diets, and a reduced reliance on external inputs like antiparasiticides. These major changes in livestock production systems may potentially result in re-emergence (or emergence) of parasitic infections. The basic objective of this paper is to give an overview of the available information on parasitic problems in organic livestock production with a focus on northern temperate regions. Furthermore, options for control that target these problems and are acceptable within the framework of organic farming will be discussed. The large majority of conventional pigs and poultry are raised in highly intensive production systems which differ dramatically from organic housing systems and especially outdoor runs and pastures. A comparably pronounced difference between conventional and organic systems is not found for ruminants. Thus, organic rearing may be a higher risk factor for pigs and poultry than for ruminants, however this may partly be counteracted by the fact that pigs and poultry never rely on pasture vegetation for feeding, while ruminants do so with associated potential problems of insufficient nutritional status and increased parasite transmission. Several studies have indicated higher parasite infections rates in organic herds vs. and conventional herds, and many of these differences may be explained by environmental factors favourable to the development of parasite oocysts/eggs/larvae and perhaps for intermediate hosts, while fewer differences may be due to the lack of chemical intervention. However, parasite species have to overcome many very diverse constraints in their attempts to complete their life cycles and it may therefore be risky to generalize. Thus, helminths and Eimeria sp. infections are most prevalent in organic swine herds whereas infections with Isospora suis seems less common than in intensive herds. A higher risk of helminth infections has also been documented in organic poultry. In organic dairy production, gastrointestinal parasites may pose a problem, and lungworm infection remains a major problem, not only in grazing heifers and steers but also in adult milking cows. This is not different from conventional herds but control measures are restricted. Many problems can be controlled by appropriate management routines, e.g. pasture management. However, avoiding chemotherapeutics for control in certain regions, e.g. in relation to ectoparasitic infections, remains a major challenge. Future research has to actively exploit new, promising avenues for control like forages or diets with anti-parasitic activities, biological control and selection for resistance, using approaches compatible with organic farming principles

Revisiting Quasiparticle Scattering Interference in High-Temperature Superconductors: The Problem of Narrow Peaks

We revisit the interpretation of quasiparticle scattering interference in cuprate high-$T_c$ superconductors. This phenomenon has been very successful in reconstructing the dispersions of d-wave Bogoliubov excitations, but the successful identification and interpretation of QPI in scanning tunneling spectroscopy (STS) experiments rely on theoretical results obtained for the case of isolated impurities. We introduce a highly flexible technique to simulate STS measurements by computing the local density of states using real-space Green's functions defined on two-dimensional lattices with as many as 100,000 sites. We focus on the following question: to what extent can the experimental results be reproduced when various forms of distributed disorder are present? We consider randomly distributed point-like impurities, smooth "Coulombic" disorder, and disorder arising from random on-site energies and superconducting gaps. We find an apparent paradox: the QPI peaks in the Fourier-transformed local density of states appear to be sharper and better defined in experiment than those seen in our simulations. We arrive at a no-go result for smooth-potential disorder since this does not reproduce the QPI peaks associated with large-momentum scattering. An ensemble of point-like impurities gets closest to experiment, but this goes hand in hand with impurity cores that are not seen in experiment. We also study the effects of possible measurement artifacts (the "fork mechanism"), which turn out to be of relatively minor consequence. It appears that there is an unknown mechanism at work which renders the QPI peaks much sharper than they are based on present theoretical understanding.Comment: 23 pages, 25 figures, published version, includes minor change

Helminth parasites in pigs: New challenges in pig production and current research highlights

Helminths in pigs have generally received little attention from veterinary parasitologists, despite Ascaris suum, Trichuris suis, and Oesophagostomum sp. being common worldwide. The present paper presents challenges and current research highlights connected with these parasites. In Danish swine herds, new indoor production systems may favour helminth transmission and growing knowledge on pasture survival and infectivity of A. suum and T. suis eggs indicates that they may constitute a serious threat to outdoor pig production. Furthermore, it is now evident that A. suum is zoonotic and the same may be true for T. suis. With these ‘new’ challenges and the economic impact of the infections, further research is warranted. Better understanding of host–parasite relationships and A. suum and T. suis egg ecology may also improve the understanding and control of human A. lumbricoides and T. trichiura infections. The population dynamics of the three parasites are well documented and may be used to study phenomena, such as predisposition and worm aggregation. Furthermore, better methods to recover larvae have provided tools for quantifying parasite transmission. Thus, an on-going study using helminth naïve tracer pigs has surprisingly demonstrated that soil infectivity with A. suum and T. suis increases during the first 2–3 years after pasture contamination. Though all three helminth species stimulate the Th2 arm of the immune system, Oesophagostomum seems weakly immunogenic, perhaps via specific modulation of the host immune system. A. suum and T. suis potently modulate the host immune response, up-regulating Th2 and down-regulating Th1. As a consequence, A. suum may compromise the efficacy of certain bacterial vaccines, whereas T. suis, which establish only short-term in humans, is a favourite candidate for down-regulating autoimmune Th1-related diseases in man. Some basic research findings have offered new possibilities for future sustainable control measures. For example, the heredity of host resistance to A. suum and T. suis is so high that breeding for resistant pigs may be a possibility. Experimental studies have demonstrated that fermentable dietary carbohydrates have an antagonistic effect on Oesophagostomum and to a lesser extent on T. suis and A. suum, whereas egg-destroying microfungi may be used to inactivate the hard-shelled A. suum and T. suis eggs in the environment. Helminth control in Denmark has previously relied solely on anthelmintic treatment in herds with low helminth transmission. When indoor transmission rates increase, or in outdoor herds with high pasture contamination levels, medication may advantageously be combined with sustainable control measures, such as selected pig genomes, bioactive forages, and egg-destroying microfungi. © 2011 Elsevier B.V. All rights reserved

Creating better superconductors by periodic nanopatterning

The quest to create superconductors with higher transition temperatures is as old as superconductivity itself. One strategy, popular after the realization that (conventional) superconductivity is mediated by phonons, is to chemically combine different elements within the crystalline unit cell to maximize the electron-phonon coupling. This led to the discovery of NbTi and Nb3Sn, to name just the most technologically relevant examples. Here, we propose a radically different approach to transform a `pristine' material into a better (meta-) superconductor by making use of modern fabrication techniques: designing and engineering the electronic properties of thin films via periodic patterning on the nanoscale. We present a model calculation to explore the key effects of different supercells that could be fabricated using nanofabrication or deliberate lattice mismatch, and demonstrate that specific pattern will enhance the coupling and the transition temperature. We also discuss how numerical methods could predict the correct design parameters to improve superconductivity in materials including Al, NbTi, and MgB

Robust procedure for creating and characterizing the atomic structure of scanning tunneling microscope tips

Scanning tunneling microscopes (STM) are used extensively for studying and manipulating matter at the atomic scale. In spite of the critical role of the STM tip, the control of the atomic-scale shape of STM tips remains a poorly solved problem. Here, we present a method for preparing tips {\it in-situ} and for ensuring the crystalline structure and reproducibly preparing tip structure up to the second atomic layer. We demonstrate a controlled evolution of such tips starting from undefined tip shapes.Comment: 12 pages preprint-style; 5 figure

Antagonistic effect of chitin-degrading microfungi on thick-shelled pig helminth eggs

The rising demand for pigs produced in organic farming systems, which require access to outdoor areas and associated increased risk of gastrointestinal nematode infections, is creating growing interest in alternative control strategies. Also development of anthelminthic resistance due to extensive use of anthelmintics is a concern in intensive pig production. Use of chitin-degrading microfungi is one of the options. Extensive research has been conducted on biological control of plant pathogenic nematodes using such fungi, and some fungal species are commercially available for plant protection. In contrast, there are only limited laboratory studies conducted on eggs from nematodes which are animal parasites. The aim of present study is to investigate the antagonistic effect of chitin-degrading microfungi on thick-shelled pig helminth eggs (i.e. Ascaris suum and Trichuris suis) both in the laboratory as well as in the field. We have performed a pilot study of the ovicidal effect of Paecilomyces lilacinus alone and in combination with chitin supplement on A. suum eggs over 4 weeks in 2% water agar. Within 1 week more than 90% of the eggs were hatched in both cases within the Petri dish as compared to controls, indicating that the fungus is capable of degrading the chitin wall so the larvae are becoming free. Soon we will proceed for full-fledged study with 2 fungal species (P. lilacinus and Pochonia chlamydosporia) which were proven to have ovicidal activity against nematode eggs. This will be done in the laboratory using soil samples amended with A. suum eggs, under semi-natural (pasture plot) conditions and finally on heavily contaminated pastures