PRELIMS

• Parasitology


  An area of biology that deals with a special group of animal (PARASITES) which are physiologically dependent on the other organisms (HOSTS)
• Types of parasites based on location in the host

  • Endoparasites
  • Ectoparasites

  
• Endoparasites


  Parasites that live inside the host, causing infection
• Erratic/aberrant parasites


  Parasites found in an organ not their usual habitat, may migrate to final habitat
• Ectoparasites


  Parasites that live outside of the host or on the surface of host's body, causing infestation

  
• Effect of parasites on host

  • Non-pathogenic
  • Pathogenic

  
• Non-pathogenic parasites


  Do not produce a disease pattern in the host, only morphological effects

  
• Pathogenic parasites


  Produce a disease pattern in the host through mechanical, traumatic or toxic activities

  
• Types of parasites based on host relationship

  • Obligate
  • Facultative
  • Intermittent
  • Incidental

  
• Obligate parasites


  Organisms that cannot exist without a host to complete their development and propagation

  
• Facultative parasites


  Organisms that may exist in a free living state but may also become parasites

  
• Intermittent parasites


  Organisms that visit the host only during feeding time

  
• Incidental parasites


  Organisms that establish themselves in a host where they do not ordinarily live

  
• Modes of parasite transmission

  • Soil transmitted
  • Snail transmitted
  • Arthropod transmitted
  • Food transmitted
  • Contact transmitted

  
• Soil transmitted parasites


  Develop further in the soil before becoming infective

  
• Snail transmitted parasites


  Develop further inside the snail before becoming infective

  
• Snail transmitted parasites


  • Schistosoma japonicum
  • Schistosoma mansoni
  • Paragonimus westermani

  
• Arthropod transmitted parasites


  Develop further within an arthropod (insect) before becoming infective

  
• Arthropod transmitted parasites


  • Plasmodium (malaria)
  • Trypanosoma gambiense

  
• Food transmitted parasites


  Develop in the flesh of animals (food) before becoming infective

  
• Food transmitted parasites


  • Trematodes
  • Tapeworms
  • Fasciola hepatica

  
• Contact transmitted parasites


  Do not develop further, are readily infective upon contact

  
• Contact transmitted parasites


  • Trichomonas
  • Enterobius vermicularis

  
• Types of hosts


  • Definitive host
  • Intermediate host
  • Reservoir host
  • Accidental host
  • Paratenic host
• Definitive host


  Harbors the sexual/adult stage of the parasite in its final habitat

  
• Intermediate host


  Harbors the larval/asexual stages of the parasite

  
• Reservoir host


  Other animals that harbor the parasites and allow continuity of the life cycle
• Accidental host


  Organisms infected by parasites not normally associated with them

  
• Paratenic host


  Harbors the infective stage of the parasite but no development or multiplication takes place, just transports the infective stage to the final host

  
• Definitive host


  Usually the definitive host
• Accidental host


  • Are organisms infected by (P) that are not normally associated with them
  • Could establish parasite that is not usually its parasite

  
• Accidental host


  • Hymenelopis diminuta (Rat tapeworm) - Incidental (parasite) of the human

  
• Paratenic host


  Harbors the infective stage of (P) but no development nor multiplication takes place; it simply acts as a means of transport for the infective stage to reach the final host
• Paratenic host


  • Wild boar carrying Paragonimus metacercaria
• Carrier


  Harbors a pathogen without manifesting any signs and symptoms; can be a source of infection
• Vector (transport host)


  Are organisms responsible for transmitting the Parasites from one host to another
• Biological vector


  • Transmits the parasite only after the latter has completed its development within the host
  • Essential in the life cycle

  
• Biological vector


  • Mosquito to malarial parasites
  • Biting fly
• Mechanical vector


  • Transports the Parasites without any development
• Mechanical vector


  • House fly transferring embryonated egg