L1. Introduction

Introduction to Parasitology; General Parasitology, Main Consequences of Parasitic Diseases and Mechanisms Involved

Veterinary Parasitology focuses on problems caused by parasitic diseases, their diagnosis and control

Taxonomy:

  • REGNUM ANIMALIA
  • Phylum
  • Clasis
  • Ordo
  • Familia
  • Genus
  • Species
    • basic taxonomic unit
  • Prokayota
  • Eukaryota
    • Protozoa (single-celled)
    • Metamonada
      • Diplomonadida (Giardia)
    • Parabasala
      • Trichomonadida (Trichomonas)
    • Euglenozoa
      • Kinetoplasta → Trypanosomatida (Trypanosoma, Leishmania)
    • Alveolata
      • Coccidea
      • Eimeria (Eimeria, Sarcocystis, Toxoplasma)
      • Cryptosporida (Cryptosporidium)
      • Adeleida (Hepatozoon)
      • Haematozoea (Plasmodium, Babesia, Theileria)
    • Amoebozoa
      • Entamoebida
    • Microsporidia
      • Microsporida (Encephalitozoon) - FUNGI?
    • Metatozoa (Animalia) (Multicellular)
    • Helminths
      • platyhelminths (flatworms)
      • nematoda (roundworms)
      • acanthocephala (thorny-headed worms)
    • Arthropoda
      • Acarina (ticks, mites)
      • Insecta (flies)

Interspecific Relationships

Symbiosis: both partners complement each other

  • any organism that spends a portion or all of its life intimately associated with another organ…
  • phoresis, commensalism, mutualism, …

Phoresis

  • a type of symbiotic relationship in which one organism (the smaller phoront) is mechanically carried on or in another species (host)
  • there is no biochemical dependence

Mutualism: both partners benefit each other

  • occurs when each member of the association benefits the other
  • cleaning symbiosis is a specific subtype of mutualism where certain animals known as cleaners remove ectoparasites, bacteria, and diseased and injured tissue from cooperating hosts

Commensalism: one partner benefits, the other is not harmed

  • may be facultative or obligate

Parasitism: one partner benefits, the other is harmed

Parasitism

Parasitism: an association where one of the partners is harmed and the other lives at the expense of the other

Parasite: an organism which lives at least part of its life cycle on or within another organism (the host) upon which it is physiologically and metabolically dependent and to which it causes harm in some way

Metabolic Dependency (=Feeding Mode)…

Obligate Parasite: a parasite which is completely dependent on the host during a segment or all of its life cycle e.g Fasciola hepatica

Facultative Parasite: an organism that exhibits both parasitic and non-parasitic modes of living and does not absolutely depend on the parasitic way of life, but is capable of adapting to it if placed on a host e.g. Naegleria fowleri

Accidental Parasite: when a parasite attacks an unnatural host and survives e.g. Hymenolepis diminuta (rat tapeworm)

Erratic Parasite: when a parasite wanders into an organ in which it is not normally found e.g. Entamoeba histolytica in the liver or lungs of humans

Final Host (Definitive Host): a host that harbours a parasite in the adult stage or where the parasite undergoes sexual reproduction

Intermediate Host (IH): harbours the larval stages of the parasite or an asexual cycle of development takes place. In some cases, larval development is completed in two different intermediate hosts, referred to as the first and second intermediate hosts

Paratenic Host (PH): a host that serves as a temporary refuge and vehicle for reaching an obligatory host, usually the definitive host, i.e. it is not necessary for the completion of the parasite’s life cycle

Aberrant Host (RH): a host in which a parasite cannot persist for a longer period or develop

Monoxenous Life Cycle: characterises a parasite whose development is restricted to a single host species

Heteroxenous Life Cycle: characterises a parasite whose development involves several host species

Host Specificity

  • stenotic
    • absolute host specificity e.g. human tapeworm located only in intestines
  • eurixic
    • specific to multiple hosts e.g. Fasciola hepatica found in liver an

Topic Specificity

  • location specificity
    • e.g. Eimeria mitis located in large intestine
    • e.g. Eimeria tenella located in cecum

Seasonal Specificity

  • can only be found in or on the host during certain periods of the year
    • e.g. mites in autumn and winter
    • e.g. mosquitos May-September

Age Specificity

  • parasites are typical for young animals due to underdeveloped immune system, or very old animals
    • e.g. Parascaris equuorum typical in foals from 2 months - 3 years

Protozoology: study of microscopic one-celled organisms (protozoa)

Helminthology: helminths (Cestoda [flatworms], Nematoda [roundworms], Trematoda [flukes], Acanthocephala [thorny-headed worms])

Arachnoentomology: Arthropods (Arachnids [ticks, mites], Insecta [flies, mosquitoes, lice, fleas])