1.1 Introduction
The primary aim of this book is to provide a âstudent-friendlyâ introduction to Veterinary Parasitology for those aspiring to become veterinarians, veterinary nurses or veterinary scientists. It also offers an accessible resource for those already qualified and wishing to refresh or expand their general knowledge of the topic. Others engaged in the many and varied facets of animal health and veterinary public health will also find information relevant to their interests.
This first chapter explores the nature of parasitism while Chapters 2â7 examine clinically relevant relationships and interactions between the parasite, its host and the environment. Finally, Chapters 8 and 9 recognise that, in the real world, veterinarians and animal health workers are not usually presented with a parasite as such, but with a problem concerning some bodily dysfunction affecting a flock, herd or individual.
To fulfil the aims of this book, the emphasis throughout has a clinical bias. Academic information is restricted to that necessary to gain a broad understanding of the pathogenesis, epidemiology, diagnosis and control of the commonest parasitic diseases. Key words are defined in the text or, if printed in a blue typeface, explained in a nearby âHelp boxâ. A glossary is provided on the website that accompanies this book.
Wherever possible, concepts are described in straightforward language, and unnecessary jargon or detail is avoided. Further aids to learning are provided in âHelp boxesâ, while âExtra Information Boxesâ offer additional insights for more advanced readers. Cross-references within the book are given in the format (see Section 9.2.3), (see Table 9.10) etc. These are to assist readers who may wish to follow up on particular points, but they can otherwise be ignored.
The emphasis with regard to parasite identification and the diagnosis of associated disease is on âhow itâs doneâ rather than âhow to do itâ. Latin names and taxonomic relationships are introduced only where these provide a useful foundation for comprehension, learning or further reading. The number of parasites that might be encountered in veterinary practice is so great that to mention them all would transform this âguide to learningâ into an encyclopaedia, which would defeat the purpose of the book. Selected examples are therefore given to provide an understanding of underlying principles and to illustrate the range and diversity that exists within the wonderful world of Veterinary Parasitology.
Help box 1.1
Definition of some key technical terms
- Aetiology/ aetiological agent: the cause or origin of a disease.
- Biotic potential: an expression of the rate at which a parasitic species can multiply. It depends on the number of offspring produced (âfecundityâ) and the number of generations each year (âgeneration timeâ).
- Endemic: a term used to describe a population or area within which a pathogen is established, replicating and being transmitted between hosts.
- Epidemiology: the science that describes and explains patterns of disease in the host population (i.e. the distribution and determinants of disease).
- Eukaryote: an organism with a cytoskeleton and complex subcellular structures enclosed within membranes (including a nucleus containing chromosomes). Examples: protozoa and metazoa.
- Incidence: the number of new cases of infection per unit time.
- Pathogen/pathogenicity/pathogenesis: an organism that causes disease / the severity of the damage caused / the mechanism of the disease process.
- Prevalence: proportion of host population infected at a point in time.
- Prokaryote: an organism without a nucleus or other membrane-bound subcellular structures; DNA in circular plasmid. Example: bacteria.
- Species: the basic unit of biodiversity. Although everyone knows what a species is, there is no exact definition as boundaries are often blurred. Two commonly cited definitions are: âa group of organisms capable of interbreeding and producing fertile off-springâ and âa separately evolving lineage that forms a single gene-poolâ.
- Taxonomic: relating to the laws and science of describing, identifying, naming and classifying organisms.
1.1.1 What is Veterinary Parasitology?
Animal disease can have noninfectious or infectious origins. Noninfectious diseases result from genetic defect, physiological abnormality, structural dysfunction or external factors such as injury, ...
