Medical and Public Health Parasitology

• Main focus of the Parasite-Host Relationship

  • Recognition of these relationship
  • search for patterns of the relationship
  • development of methodologies to study these patterns
• Types of Parasites :

  1. Obligatory parasite
  2. Facultative parasite
  3. Endoparasite
  4. Ectoparasite
• Obligatory Parasite - parasite that cannot survive outside of a host, needd to be inside of the host to survive (e.g, virus)
• Facultative Parasite - capable of existing independently of a host (eg., strongyloides)
• Endoparasite - established inside the host (e.g., plasmodium)
• Ectoparasite - lives on or near the surface of the body (e.g., flea)
• According to Pathogenecity

  • Pathogenic - can cause disease (entamoeba histolytica)
  • Non-pathogenic - cannot cause disease (other amoeba spp.)
• According to need for host :

  • Obligate - need host
  • Facultative - need the nutrient of the host
  • Accidental / Incidental - by accident
• According to number of hosts required in the life cycle :

  • Monoxenus - direct life cycle ; one host
  • Heteroxenus - indirect life cycle ; two host as part of their life cycle
• Types of Host :

  1. Accidental / Incidental Host
  2. Definitive Host
  3. Intermediate Host
  4. Reservoir Host
  5. Transport Host / Paratenic / Phoretic
  6. Carrier
• Accidental / Incidental Host - host other than the normal one that is harboring a parasite; not normal to it’s parasite
• Definitive host - host in which the adult sexual phase of parasite development occurs
• Intermediate host - host in which the larval asexual phase of parasite development occurs
• Reservoir Host - host harboring parasites that are parasiti for humans and from which humans may become infected
• Transport host / Paratenic / Phoretic - host responsible for transferring a parasite from one location to another
• Carrier - parasite - harborinh host that is not exhibiting any clinical symptoms but can infect otherd. Carries the pathogen.
• Parasite-Host Relationship :

  1. Symbiosis
  2. Commensalism
  3. Mutualism
  4. Parasitism
  5. Pathogenic
• Symbiosis - living together; the association of two living organisms, each of 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 one at the other’s expense.
• Pathogenic - parasite that has demonstrated the ability to cause disease
• Parasitic life cycle ranges from simple to complex
• Three common components :

  • Mode of transmission
  • Infective Stage
  • Diagnostic Stage
• Mode of transmission - transferred to the SH
• Infective Stage - infect the SH
• Diagnostic stage - identification of thw parasite that infected the SH
• Some parasites require only a definitive host, whereas others also require one or more intermediate hosts.
• Direct life cycle - only one host in the entire life cycle
• Indirect life cycle - two or more hosts in the life cycle
• Nomenclature of Parasites :

  • The scientific name of parasites is written in italics and consist of two components genus and species
• Nomenclature of Parasites :

  • When a parasite name first appears in a document. The entire parasite name is written.
• Nomenclature of Parasite :

  • Referencing of parasite can be abbreviated by recording only the first letter of the genera followed by a periox. Followed by the entire species name.