Georgis' Parasitology for Veterinarians E-Book

Dwight D. Bowman

• Publisher: Saunders
• Year: 2020
• ISBN:
  9780323543972
• Edition: 11
• Topic: Médecine
• Subtopic: Médecine vétérinaire

Georgis' Parasitology for Veterinarians, 11 th Edition provides the most current information on all parasites commonly encountered in veterinary medicine, including minor or rare parasites to assist in the diagnosis of difficult cases. While primarily focused on parasites that infect ruminants, horses, pigs, dogs, and cats, this comprehensive text also covers organisms that commonly infect laboratory animals and exotic species. More than 600 high-quality, color photographs and illustrations help you learn how to easily identify and treat parasites of every kind.

• The most comprehensive parasitology content available, written specifically for veterinarians, provides complete information on all parasites commonly encountered in veterinary medicine, as well as information about minor or rare parasites.
• High-quality color photographs and illustrations make the process of identifying and treating parasites more accurate and efficient.

• NEW! Updated vaccines chapter keeps you up to date with what's currently happening in the field, as well as future prospects.
• NEW! Sections on new compounds in antiparasitic drugs provide coverage of the latest developments.
• NEW! Updated chapter on vector-borne diseases offers more in-depth detail on this topic.
• NEW! Enhanced eBook on Student Consult contains chapter review questions and answers, flashcards, and canine and feline parasite posters to help increase your retention of difficult subject matter.
• NEW! Updated chapter on parasite diagnostics includes new pictures and plates.
• NEW! Updated drug tables offer the most current information on drugs, vaccinations, and parasiticides.

1: Introduction

Common terms in parasitology

A parasite is a smaller organism that lives on or in and at the expense of a larger organism called the host. A louse is a parasite and so is a virus. The host’s expenses in supporting its parasites may be trivial, or they may be substantial or even unbearable. This depends on the number of parasites, the kind and degree of injury they inflict, and the vigor and nourishment of the host. A series of terms (e.g., mutualism, commensalism, parasitism) have been defined to express the degree of unilateral or mutual injury or benefit that is characteristic of particular symbiotic relationships. As a matter of convention, however, if the smaller organism is found in association with humans or with animals or plants that humans esteem, it is called a parasite, whether its presence is detrimental, indifferent, or beneficial. This convention is adopted in this book and is harmless enough, provided we remember that parasites vary in pathogenicity.

A species of animal is an interbreeding natural population that is reproductively isolated from other such populations. For example, there are two species of rather distantly related ascarid parasites of dogs: Toxocara canis and Toxascaris leonina. These two species are sufficiently similar in size and appearance to present some difficulty in their differentiation, but although they may share the small intestine of the same dog, they never interbreed. The consequent distinctness of their genetic material is expressed in modest differences in structure and in very substantial differences in life history. T. canis and T. leonina, however, share enough similarities to make their kinship obvious. We assume that these similarities stem from the evolution of both species from common ancestral stock (divergent evolution) because the number and nature of the similarities induce us to reject the alternative explanation—that is, that they represent the adaptations of unrelated forms to the same selection pressures (convergent evolution). We recognize kinship of T. canis and T. leonina by considering both to be members of the same zoologic order (Ascaridida); each is a leaf, if you will, on the same evolutionary branch.

Conventions of taxonomic classification

Peopl...