Helminth Infection

9 Key excerpts on "Helminth Infection"

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  eBook - PDF

  Principles of Medicine in Africa

  • David Mabey, Geoffrey Gill, Eldryd Parry, Martin W. Weber, Christopher J. M. Whitty(Authors)
  • 2013(Publication Date)
  • Cambridge University Press

    (Publisher)

  Section 8 Chapter 46 Helminth Infections Intestinal helminths Michael Brown, Donald A. P. Bundy and Simon Brooker Intestinal nematode infection: the problem in Africa and strategies for control Parasitic worms may be the commonest agents of chronic infection in humans There are approximately 25 major Helminth Infections of humans that all, to some extent, have public health significance (Warren et al., 1993), but amongst the most common of all human infections are the intestinal nematodes. Recent global estimates indicate that more than one-quarter of the world’s population is infected with one or more of the most common of these parasites: the roundworm, Ascaris lum- bricoides; the hookworms, Necator americanus and Ancylostoma duo- denale; and the whipworm, Trichuris trichiura. The burden of other intestinal nematodes, including Strongyloides stercoralis and Entero- bius vermicularis, are ill-defined due to practical difficulties in diag- nosing sub-clinical infections. Cestodes are also of major public health and economic importance. In Africa, Helminth Infection is most prevalent among rural communities (but also occurs in urban areas) in warm and humid equatorial regions and where sanitation facilities are inadequate. Even within areas of low prevalence, small localized areas of high prevalence can exist. The distribution of helminths amongst hosts is over-dispersed: whilst the majority of hosts harbour few or no worms, a few harbour much larger numbers of parasites. This fact has clinical consequences for the host, as it is the intensity of infection that is the central determinant of the severity of morbidity. Maximum intensity of hookworm infections is usually not attained until 20–25 years. In contrast, as shown in Fig. 46.1, the age–intensity profile for Trichuris trichiura and Ascaris lumbricoides is typically convex with maximum intensity at 5–10 years of age.

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  Parasitic Infections in the Compromised Host

  • Peter D. Walzer, Robert M. Genta(Authors)
  • 2020(Publication Date)
  • CRC Press

    (Publisher)

  8The Host Immune Response Against Parasitic Helminth Infection

  THOMAS B. NUTMANLaboratory of Parasitic Diseases, National Institutes of Health, Bethesda, Maryland

  I. Introduction

  Although major strides have been made in controlling certain helminth parasitic infections, either through transmission control schemes or new chemotherapeutic agents, some of these diseases continue to cause considerable morbidity and mortality throughout the developing world. Indeed, filariasis and schistosomiasis have each been estimated to affect over 100 million people worldwide. The reason for the high prevalence and continued transmission of these infections is in part due to the inability to find methods for inducing protective immunity to parasites. As the impact of parasitic infections is significant in terms of both their effects on individual health and the socioeconomic status of communities at large, methods for combatting them have focused increasingly on finding means to induce protective immune responses. As a consequence, great emphasis has been placed on investigating the unique relationship that exists between the parasite and the hose immune system.

  The focus of this chapter is on delineating the various aspects of the host immune response to parasitic Helminth Infection in an attempt to understand how or whether an effective immune response occurs in response to infection and how helminth parasites induce disease. While many of the recent developments in knowledge have been made possible by the large body of work done using animal models, this chapter will largely center on studies in humans.

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  Handbook of Helminthiasis for Public Health

  • D. W. T. Crompton, Lorenzo Savioli(Authors)
  • 2006(Publication Date)
  • CRC Press

    (Publisher)

  3 1 Helminthiasis — A Challenge to Health and Development There is now wide agreement in the clinical and biomedical science communities that helminthiasis has greater public health significance than was previously thought and that action to relieve and reduce its debilitating effects on the health and livelihoods of millions of poor people deserves high priority. We have written this book to support all who are concerned to confront and overcome helminthiasis. Although we may enjoy explaining how helminths travel from host to host and we may marvel at how these remarkable animals obtain food and shelter in an immuno-competent environment, we have sought to concentrate on the fact that helminths are agents of human disease. Although many species of worm have been retrieved from humans, we consider that species listed in Table 1.1 and those whose names are shown in bold type in the list compiled by Coombs and Crompton (1991) merit most attention in the context of public health. Coombs and Crompton’s list as revised by Isabel Coombs is shown at the end of the chapter. Readers are also referred to the annotated checklist of parasites published by Ashford and Crewe (1998). The worms that challenge health and development thrive and persist in econom-ically impoverished countries. Millions of people are infected and millions live with the risk of infection. In 1978, Willy Brandt chaired an independent commission that reported on global development issues. The commission divided our world into the affluent North and the impoverished South (Brandt Report, 1980). In this handbook we have retained the terms North and South as convenient if simplistic shorthand to stress where affluence and poverty prevail (Figure 1.1). The North includes member states of the G8, the OECD (Organization for Economic Co-operation and Development), the EU (European Union), the Paris Club and the dominant members of the WTO (World Trade Organization).

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  Applied and Economic Zoology

  • Rathoure, Ashok Kumar(Authors)
  • 2021(Publication Date)
  • Daya Publishing House

    (Publisher)

  Pinworms, hookwormsand roundworms are extremely common intestinal Helminth Infections of humans; worldwide, roundworms are probably the most common. Pinworm transmittal generally occurs through ingestion of fecal contaminated material and infection occurs commonly in children. Other Helminth Infections are vectored as filarial worms by insects such as mosquitosor the filaria may penetrate directly through the skin from water or soil. Filarial worms cause such diseases as river blindness ( Onchocerca volvulus ) and elephantiasis which are major health problems in some third world countries. Most Helminth Infections of This ebook is exclusively for this university only. Cannot be resold/distributed. humans can be controlled by public health programmes, public education, vector control, intermediate host control and anthelminthic drugs. Helminth Parasites The word helminth is a general term meaning worm, but there are many different types of worms. Prefixes are therefore used to designate types such as platyhelminths for flat-worms and nematohelminths for round-worms. All helminths are multicellular eukaryotic invertebrates with tube like or flattened bodies exhibiting bilateral symmetry. They are triploblastic (with endo, meso and ecto-dermal tissues) but the flatworms are acoelomate (do not have body cavities) while the roundworms are pseudocoelomate with body cavities not enclosed by mesoderm. In contrast, segmented annelids such as earthworms are coelomate with body cavities enclosed by mesoderm. Many helminths are free living organisms in aquatic and terrestrial environments whereas others occur as parasites in most animals and some plants. Parasitic helminths are an almost universal feature of vertebrate animals; most species have worms in them somewhere. Three major assemblages of parasitic helminths are recognized; Nemathelminthes (nematodes) and Platyhelminthes (flatworms), the latter being subdivided into Cestoda (tapeworms) and the Trematoda (flukes).

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  Medicine and Evolution

  Current Applications, Future Prospects

  • Sarah Elton, Paul O'Higgins, Sarah Elton, Paul O'Higgins(Authors)
  • 2008(Publication Date)
  • CRC Press

    (Publisher)

  106,107 Again, if our conjectures are correct, another tragic side effect of helmin-thic infection in hominins is that the worms that we harbor today have been with us for thousands if not millions of years. This does not mean that main-taining large worm burdens is not costly to hosts, but rather that the majority of humans have lost, and continue to lose, this host-pathogen arms race. It would be interesting to come up with an approximate number for the total volume of the helminth biomass that humans harbor in their intestines in the world today, to divide that number by the total volume of the biomass of human hosts, and then to do the same calculation for indigenous versus nonindigenous rural and urban groups in developed and underdeveloped countries. This would give us a better appreciation for the energy that hel-minthes are extracting from humans on a macroscale. The evolutionary implications of this helminth-centered view of human biology in the twenty-first century are considerable. How much of the energy that humans now invest directly or indirectly in defense against helminthes could be diverted into other fitness- and health-enhancing physiological functions across the life course if helminthes could be eradicated from the planet? How would that affect global health patterns? In addition to the more obvious effects, such as healthier overall developmental trajectories for children, and a longer, healthier life span, the impact of helminth eradica-tion on the rates of emergence of new viral and bacterial infections, and the rates of transmission of their older counterparts, could be significant. If in fact helminthes make hosts more susceptible to pathogenic viruses and bac-teria through mechanisms that downregulate the cells involved in the Th1 response, then, on a global scale, eradication of helminthes would in effect lead to a reduction of the number of susceptibles to new and old viral and bacterial infections.

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  Biodiversity

  Threats and Conservation

  • R C Sobti(Author)
  • 2022(Publication Date)
  • CRC Press

    (Publisher)

  Also, there is a written evidence about Helminth Infections from the ancient literature of Hippocrates, Egyptian medical papyri, and the Bible (Hotez et al., 2008). Breaking this long-standing relationship between the helminth and humans could have immediate effects on our immune system. Following adaption to the micro-environment within their definitive host, the helminth parasites establish a successful host-parasite relationship by overcoming the host-mounted rejection responses. Helminths are known to synthesize and excrete/secrete a number of immunomodulatory molecules that help in their successful establishment by altering both the innate and adaptive immune responses (Ryan et al., 2020). Some of the immunomodulatory molecules derived from the liver flukes, Fasciola spp., are summarized in Figure 26.1. It is assumed that a complete eradication of the Helminth Infection might remove an important immune regulator that could give rise to an autoimmune disease and exaggerated inflammatory responses. In the present communication, we discuss about the increasing evidence for helminth-host interactions that suggest the possible roles of helminth and their derived products for the prevention and control of immune-mediated disorders. FIGURE 26.1 Major immunomodulatory molecules of liver fluke, Fasciola spp. 26.3 Helminths and Inflammatory Bowel Disease Inflammatory bowel disease (IBD) is a collective term used to describe disorders like ulcerative colitis and Crohn’s disease, involving chronic inflammation of the digestive tract. Although the actual reasons for these inflammatory diseases still remain a mystery, it is assumed that they arise from inappropriately aggressive mucosal immune responses to the luminal substances. Recent studies have highlighted the impact of different genetic alterations in imparting risk for or protection from acquiring these conditions

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  Parasitism and Parasitic Control in Animals

  Strategies for the Developing World

  • Hafiz Muhammad Rizwan, Muhammad Sohail Sajid, Hafiz Muhammad Rizwan, Muhammad Sohail Sajid(Authors)
  • 2023(Publication Date)
  • CAB International

    (Publisher)

  Parasitism and Parasitic Control in Animals: Strategies for the Developing World (eds H.M. Rizwan and M.S. Sajid)

  DOI: 10.1079/9781800621893.0002 Abstract

  Parasites induce multiple pathological changes in their human and animal hosts. In this chapter, the pathophysiology of parasitic infections and their clinical symptoms are discussed. Pathways for pathology of parasitic infections might be associated directly (e.g. intestinal blockage and damage by the helminths) or indirectly (e.g. loss of production through reduced feed intake or reduced feed conversion ratio). Similarly, haemoprotozoa are discussed to study their effects on blood (cell count, anaemia, etc.). Nematodes and cestodes are discussed for their special association with the gastrointestinal (GI) tracts of their hosts. Parasites mostly cause production and economic losses in livestock by affecting their GI functions, feed intake, efficiency of feed conversion into protein mass and energy metabolism. In this chapter, we describe the pathogenic interventions of numerous parasitic infections of livestock along with their prevalent genera and species in developing countries. Information on the harmful impacts of these parasites will aid future researchers in developing measures to combat them. This chapter has concentrated the essence of multiple studies related to parasitic infection pathology.

  2.1 Introduction

  Parasitic infestations in livestock are one of the major limiting factors affecting animal productivity and global food security. Among various parasitic diseases, helminths are responsible for severe pathology accompanied by a decline in animal health and hence lead to economic losses. Most parasites cause infectious diseases in their hosts (Olano et al., 2011). Some parasites also act as intermediate/transport hosts or vectors (mechanical or biological) for a wide range of microorganisms, exaggerating the pathological status of the infected hosts (Aktas et al., 2015).

  Anti-inflammatory factors maintain local homeostasis in the central nervous system (CNS). Anti-inflammatory substances sustain fragile neural networks in this immunologically specialized environment. When a foreign pathogen or parasite invades the CNS, the immune system responds by releasing a mixture of immunological molecules that trigger a cascade of responses to control the infection and its consequences (Nicholson, 2016). However, a host–parasite link can develop, in which two complicated organisms develop a tight biochemical coevolution and communication at all organizational levels. The parasite’s ability to establish itself in its host is linked to multiple immune-evasion mechanisms to enable it to exploit host-derived components. In this circumstance, the CNS interacts with the growth factors, neuropeptides and hormones which are examples of evolutionarily conserved compounds to modulate immunological processes, whether protective or pathogenic, and possibly parasite activity as well (Adalid-Peralta et al., 2018). Many CNS-related parasitic infections generate different morbidity and mortality grades in low and middle-income countries, highlighting how the CNS milieu impacts pathogen establishment, development, survival and reproduction in immunocompetent hosts. A full understanding of the impact of the CNS microenvironment on neuro-infections could lead to new insights into disease processes (Carpio et al

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  The Biology of Nematodes

  • Donald L Lee(Author)
  • 2002(Publication Date)
  • CRC Press

    (Publisher)

  Haemonchus contortus, a parasite of sheep, goats, cattle and deer, was introduced by Stoll (1929) to describe immunity to a nematode infection (Ackert 1942), we have acquired an array of experimental and clinical host-nematode systems in which immunity occurs in the host. In this chapter we will describe immune responses characteristic of nematode infections and focus on the effector functions of immune systems, which cannot be understood separately from nematode biology. The immune responses to parasitic nematodes should bring us real insight into the biology of nematodes.

  Overview of Host-Parasitic Nematode Interactions

  It is essential to know the basic behavioural patterns of animal-parasitic nematodes to understand the immu-nology of nematode infections. In the phylum Nematoda the parasitic mode of living has been employed several times independently (Blaxter et al., 1998). In mammalian hosts nematodes may parasitise the eye, mouth, tongue, gastrointestinal tract, liver, lungs, muscle, connective tissue, brain, lymphatics, blood or body cavity. They can be found virtually everywhere. In spite of various life cycles, which range from the very simple to the extremely complicated, and of the phylogenetic distance between groups of parasitic nematodes, it is possible to find common motifs of nematode behaviour in the nematodes of animals and humans.

  Principles of Parasitic Nematode Life Cycles

  Infective larvae

  All animal-parasitic nematodes are ‘endoparasites’, meaning parasites inside the host body. Theoretically endoparasites can be divided further into two categories. One group of parasites lives in the alimentary tract and its annex without invading the host tissue and the other enters the host body with tissue invasion. However, practically all parasitic nematodes in mammals penetrate covering epithelia of the host, namely the skin or the mucosa of the gastrointestinal tract, to enter the host body even though their final destination may be the gastrointestinal lumen. In general, parasitic nematodes enter the host when they are third-stage larvae (L3), which are thus referred to as ‘infective larvae’, and enter the vertebrate host orally or percutaneously. Oral infection takes place as the host drinks or ingests food that is either contaminated with eggs or larvae, or is parasitised by larvae. Larvae swallowed or hatched from eggs in the alimentary tract may immediately penetrate the epithelial layer to reach the mucosal tissue. Some species remain in the alimentary tract and others start extensive migrations (Figure 18.1

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  The Biology of the Laboratory Rabbit

  • Steven H. Weisbroth, Ronald E. Flatt, Alan L. Kraus, Steven H. Weisbroth, Ronald E. Flatt, Alan L. Kraus(Authors)
  • 2013(Publication Date)
  • Academic Press

    (Publisher)

  Helminth Parasites Richard B. Wescott I. Introduction II. Natural Infections . . A. Nematodes . . . . B. Cestodes C. Trematodes . . . III. Experimental Infections A. Ruminants . . . . B. Swine C. Small Animals . . D. Man IV. Conclusions References I. INTRODUCTION Natural Helminth Infections do not present a serious problem in rabbits raised for biomedicai research if proper husbandry practices are followed. Occasionally investi-gators find their experimental subjects infected with Passa-luris ambiguus, the rabbit pinworm. From time to time other helminths, common in wild rabbits, are reported in domestic rabbits. In general, these natural infections are regarded as a nuisance and diagnosis is made because of curiosity. The actual importance of the infections is that several are excellent experimental models for parasito-logical research. In addition to such parasitism, many important Helminth Infections of man and domestic animals may be produced experimentally in domestic rabbits. A number of these also represent valuable experimental models. For this reason, both natural and experimental Helminth Infections of domestic and wild rabbits are con-sidered in this chapter. CHAPTER 13 317 317 318 322 323 324 . . . . 324 325 325 325 326 326 Consideration of natural Helminth Infections is limited to those parasites that are prevalent in wild rabbits or serve as experimental models. A short description of morphology is provided for diagnostic purposes and usefulness as research models is noted when appropriate. The review of experimental Helminth Infections is limited to those that are useful research models or are important parasites of man and domestic animals. A number of these infections occur in wild rabbits under natural conditions but they are listed in the experimental infection category if the rabbit is not considered the normal host. The morpho-logy of these parasites is not reviewed. Consideration is given only to their reported research value.

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