WEEK 13

• Symbiosis


  A relationship where unlike organisms exist together
• Forms of symbiotic relationship


  • Commensalism
  • Mutualism
  • Parasitism
• Parasite


  Organism which lives on or within some other living organisms deriving sustenance from it, the organism in which he lives is a host
• Important elements in parasitism

  • Parasite
  • Host
• Classification of parasites based on habitat

  • Ectoparasites (e.g. fleas, lice)
  • Endoparasites (e.g. helminths or worms)
• Infestation


  Invasion of the body by ectoparasites
• Infection


  Invasion of the body by endoparasites
• Parasites based on ability to live independently of the host

  • Facultative parasites
  • Obligate parasites
• Parasites based on mode of living

  • Permanent parasite
  • Intermittent parasite
  • Incidental parasite
  • Transitory parasite
  • Erratic parasite
• Classification of hosts


  • Definitive hosts
  • Intermediate hosts
  • Reservoir hosts
  • Paratenic hosts
• Sources of exposure to infection or infestation

  • Contaminated soil
  • Contaminated water
  • Blood-sucking insect
  • Domestic or wild animal
  • Human beings
  • Ones-self / Autoinfection
• Modes of transmission (MOT)


  • Ingestion of contaminated food & water
  • Transmitted by ingestion of contaminated water
  • Transmitted from eating food containing mature larval stages
  • Enter body from soil via skin from fresh water
  • Bite of blood-sucking arthropods
  • Inhalation of airborne
  • Transplacental or congenital infection
  • Transmamammary (milk) infection
  • Sexual intercourse
• Portal of exit of parasites

  • Anus
  • Urine
  • Sputum
• Pathogenesis


  The dynamics of any disease process
• Ways in which parasites produce damage to the host

  • Trauma or physical damage
  • Lytic necrosis
  • Stimulation of host tissue reaction
  • Toxic & allergic phenomena
  • Opening of pathways for entry of other pathogens into tissues
• Inapparent infection


  No symptoms
• Examples of parasitic damage

  • Traumatic damage (e.g. entry of infective larvae of hookworms or blood flukes)
  • Lytic necrosis (enzymes produced necessary for food)
  • Stimulation of host tissue reaction (increase eosinophils)
  • Toxic & allergic phenomena (hypersensitivity reaction)
• Anthelmintic


  A remedy used to reduce the number of helminths in animals or humans
• Anthelmintic resistance


  A change in gene frequency of a helminth population, produced by drug selection which renders the minimal effective dosage, previously used to kill a defined portion (e.g. 95%) of the population, no longer equally effective
• Assassin bug


  An insect of the order Hemiptera, in the family Reduviidae, which may cause painful bites
• Basis capituli


  The anterior part of the body of mites and ticks from which the mouthparts project forward
• Capitulum


  The anterior body part of mites and ticks including the mouthparts; also known as the gnathosoma
• Parasitology is significant in public health, agriculture, and ecology for understanding and mitigating parasitic diseases
• The role of nurses (or nursing students) is to promote awareness and help mitigate parasitic diseases