Chapter 1: Introduction

• The study of parasites, organisms that live on and obtain their nutrients from another organism, a field known as parasitology.
• Host - the animal or plant upon which a parasite lives
• Parasite - an organism living at the expense of another organism
• Vector - an intermediate host (animal) between two hosts
• • Infection -  invasion IN the Body
• • Infestation - invasion ON the body
• Epidemiology - study of distribution and determinants of health-related states or events in specified populations
• Disease - illness caused by infection/infestation
• Populations at Risk for Contracting Parasites

  • Individuals in underdeveloped areas and countries
  • Refugees
  • Immigrants
  • Visitors from foreign countries
  • Individuals who are immunocompromised
  • Individuals living in close quarters (e.g., prisons)
  • Children who attend day care centers
• The main focus of this research has been threefold:

  1. Recognition of these relationships;
  2. Search for patterns of the relationships;
  3. Development of methodologies to study these patterns.
• Type of Parasite

  Obligatory Parasite

  Parasite that cannot survive outside of a host

  Facultative Parasite

  Parasites that is capable of existing independently of a host

  Endoparasite

  Parasite that is established inside of a host

  Ectoparasite

  Parasite that is established in or on the exterior surface of a host
• Parasite-Host Relationship Terms

  Symbiosis

  Living together; the association of two living organisms, each of a different species

  Commensalism

  Association of two different species of organisms that is beneficial to one and neutral to the other

  Mutualism

  Association of two different species of organisms that is beneficial to both

  Parasitism

  Association of two different species of organisms that is beneficial to one at the other’s expense
• Three Common Components:

  1. A mode of transmission, 
  2. A morphologic form that invades humans, known as the infective stage, and
  3. One (or more) forms that can be detected via laboratory retrieval methods, known as the diagnostic stage.
• Elephantiasis - an enlargement of areas such as the breast, leg, and scrotum caused by a parasite’s presence.
• Stool is the most commonly submitted sample for such studies.
• O&P, in which “O” stands for ova (eggs) and “P” stands for parasites, is still widely used today.
• Suspicious forms that visually resemble parasites in terms of size and morphology are commonly encountered and are often referred to as artifacts and/or confusers.
• microns (μm), a measurement defined as one millionth of a meter (10−6 m).
• The scientific names of parasites are written in italics and consist of two components, genus (pl., genera) and species.
• The suffix -iasis is often used to denote such diseases or conditions.
• Single-celled parasites — Protozoa are unicellular eukaryotes that are mostly parasites.
• Multicellular worms — Metazoa helminths which includes multicellular organisms such as parasitic worms.
• Arthropods (insects and their allies) — Animalia
• Parasite classification—the protozoa.

  Subkingdom: Protozoa

  Phylum: Sarcomastigaophora

  Subphylum: Sarcodina

  Class: Lobosea
• Subkingdom: Protozoa

  Phylum: Sarcomastigophora

  Subphylum: Mastigophora

  Class: Zoomastigophora (flagellates/hemoflagellates)
• Subkingdom: Protozoa

  Phylum: Ciliophora

  Class:Kinetofragminophorea (ciliates)
• Subkingdom: Protozoa

  Order: Blastocystida

  Class: Blastocystea
• Subkingdom: Protozoa

  Phylum: Apicomplexa

  Class: Sporozoa
• Parasite classification—the helminths.

  Subkingdom: Metazoa

  Phylum: Nemathelminthes

  Class: Nematoda (roundworms)
• Subkingdom: Metazoa

  Phylum: Nemathelminthes

  Class: Filariae (tissue roundworms)
• Subkingdom: Metazoa

  Phylum: Platyhelminthes

  Class: Cestoda (tapeworms)
• Subkingdom: Metazoa

  Phylum: Platyhelminthes

  Class: Trematoda (flukes)
• Parasite classification—the arthropods.

  Kingdom: Animalia

  Phylum: Arthropoda

  Class: Crustacea (crabs, crayfish, etc.)
• Kingdom: Animalia

  Phylum: Arthropoda

  Class: Arachnida  (ticks, mites, etc.)
• Kingdom: Animalia

  Phylum: Arthropoda

  Class: Insecta (insects)
• Kingdom: Animalia

  Phylum: Arthropoda

  Class: Chilopoda (centipedes)
• Kingdom: Animalia

  Phylum: Arthropoda

  Class: Pentastomida (tongue worms)