Antiparasitic

3 Key excerpts on "Antiparasitic"

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  eBook - PDF

  Natural Remedies in the Fight Against Parasites

  • Hanem Khater, M. Govindarajan, Giovanni Benelli, Hanem Khater, M. Govindarajan, Giovanni Benelli(Authors)
  • 2017(Publication Date)
  • IntechOpen

    (Publisher)

  This is termed biological control or simply biocontrol. Biocontrol is therefore defined as “any activity of one species that reduces the adverse effect of another” [ 1 ]. Biocontrol can also be defined as “the study and uses of parasites, predators and pathogens for the regulation of host (pest) densities” [2 ]. Biological control differs from natural control in that the latter does not involve human manipulation. The organism that suppresses the pest population is generally referred to as a biological control agent (BCA). A parasite is an organism that lives and feeds in or on a host [ 3]. Parasites that invade and live within the host are referred to as endoparasites; meanwhile, those that live on the surface without invading the host are referred to as ectoparasites. Endoparasites include helminths and protozoa, and ectoparasites are fleas, ticks, mites, insects and so on. Parasites are a major cause of disease in man, his livestock and crops, leading to poor yield and economic loss. The biocontrol of parasites therefore entails the use of BCAs to suppress the population of the parasites. This chapter focuses on the biological control of parasites, providing a brief history of bio ‐ control; their advantages and disadvantages; types of BCAs including predators, parasites (parasitoids) and pathogens (fungi, bacteria, viruses and virus‐like particles, protozoa and nematodes); their effect on the native biodiversity; a few case studies of successful implemen ‐ tation of biocontrol; challenges encountered with the implementation of biocontrol strategies and finally their future perspectives. 2. History of biological control The concept of biological control is not entirely new. The ancient Egyptians were probably the first to employ biocontrol dating some 4000 years ago, when they observed that cats fed on rodents, which damaged their crops. This most likely led to the domestication of the house cat [ 4]. However, the first record of biocontrol is from China.

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  eBook - ePub

  Medicinal Chemistry

  • Norma K Dunlap, Donna M Huryn(Authors)
  • 2018(Publication Date)
  • Garland Science

    (Publisher)

  Parasitic diseases affect billions of people in the world, and their incidence is increasing. In addition, certain infections, typically of little consequence, have become more prevalent and serious when they occur in immunosuppressed patients. Finally, the migration of individuals infected with parasites to low-prevalence areas has further contributed to the increase in incidence.

  Antiparasitic Drug Discovery

  Many parasitic diseases are considered neglected diseases. They are prevalent in tropical and subtropical environments and affect billions of people, who often live in poverty, in close contact with infectious vectors and without adequate sanitation. They are termed neglected because these diseases have been largely eradicated in more developed parts of the world. Treatment strategies rely on prevention, such as elimination of vectors and safe food and water sources. In addition, drug therapy needs to consider the specific patients affected and their environment. As such, low cost, short treatment regimens, and ease of administration are primary criteria.

  Many older drugs were developed on the basis of known activity against other organisms, relying on phenotypic screens. In fact, a number of antibacterial drugs are also used to treat parasitic diseases. However, the number of drugs that specifically target parasites is far fewer than the number that target bacteria. Challenges include the highly complex life cycle of some parasites and development of resistance. While there were few drugs approved from the 1970s to the 1990s, there has been an increase in activity in the development of new Antiparasitic agents in the 21st century. Advances in sequencing the genomes of these organisms and formation of private-public partnerships to support drug discovery for neglected tropical diseases are partly responsible for this change.

  Table 12.2

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  eBook - ePub

  Pharmaceutical Chemistry E-Book

  • David G. Watson(Author)
  • 2011(Publication Date)
  • Churchill Livingstone

    (Publisher)

  Chapter 25 Antiparasitic drugs

  David G. Watson

  Chapter contents

  Introduction 511

  Malaria 511

  Isoquinolines and related compounds 511

  Artemisinin and its analogues 514

  Inhibitors of folic acid biosynthesis 515

  Miscellaneous drugs 516

  Antimalarial preparations 516

  Trypanosomiasis 516

  Antitrypanosomal preparations 518

  Leishmaniasis 518

  Antileishmanial preparations 519

  Toxoplasmosis 519

  Giardiasis 520

  Trichomoniasis 520

  Preparations for the treatment of giardiasis and trichomoniasis 521

  Pneumocystis pneumonia 521

  Preparations for the treatment of pneumocystis 521

  Anthelmintics 521

  Introduction

  Most of the drugs used to treat parasitic diseases were developed over 50 years ago and the more recent developments of this type of drug have been in antimalarial drugs, since malaria is the disease which is most likely to affect travellers from the West to tropical regions. Thus many other parasitic diseases remain poorly treated because these diseases affect poorer countries which cannot afford to pay for expensive new treatments. An obvious solution to such diseases would be to vaccinate, but parasites have complex life cycles and thus it is difficult to design vaccines which promote immunity to the various stages. In addition, parasites can vary their surface antigens, which can render vaccines ineffective. Many parasites have developed mechanisms for reducing the immune response of the host by producing compounds which cause immunosuppression. It is likely, as developing countries become wealthier, that more effective and less toxic drugs will be developed to treat parasitic diseases. However, at the moment, many Antiparasitic drugs are quite toxic and have to be administered using complex dosage regimens.

  Malaria

  Isoquinolines and related compounds

  Malaria is a protozoal organism; more specifically it belongs to the sporozoan (spore forming) subclass of protozoa. These organisms are all animal parasites, whereas the majority of protozoa are not. Protozoa are single-celled organisms and generally have the complex life cycle of the malaria parasite, where they have to exist in various forms in the animal host and then transfer from the animal host to an insect vector. In the case of malaria, the insect vector is the Anopheles mosquito. There are four common forms of the causative agent of malaria: Plasmodium falciparum , which is very common and causes a severe form of the disease, and P. vivax, P. ovale and P. malariae , which cause less severe forms of the disease. The disease is estimated to cause 300 million acute cases each year which result in 1 million deaths. The life cycle of the malaria parasite in humans is summarised in Table 25.1

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