Intro

• Symbiosis


  Relationship between 2 unlike organisms
• Symbiont/Symbiote


  The members of the symbiotic relationship
• Examples of Symbiotic Relationships

  • Mutualism (both benefit)
  • Commensalism (one benefits, one is not affected/unharmed)
  • Phoretic relationship (one is carried, no physiologic interaction)
  • Parasitism (one benefits, one is harmed)
• Phoresis


  Means "to carry"
• Phoront


  Organism being carried
• Parasitology


  An area of biology that deals with the dependence of one organism on another
• Parasitology is the study of parasites, its hosts, and their relationships
• Host


  Species which harbors the parasite
• Final Host/Definitive Host


  Harbors the mature form of the parasite, sexual reproduction and maturity takes places in these hosts, common FH are man
• Intermediate Host


  Harbors immature/larval form of the parasite, asexual reproduction takes place
• Vectors


  Responsible for transmission
• Types of Vectors


  • Biologic Vector (there is morphologic change or transformation of parasite before transmission to another host, parasite is always inside)
  • Mechanical/Phoretic Vector (no morphologic change occurs, parasite always outside)
• Accidental Host


  Host that harbors a parasite that usually does not infect it
• Paratenic Host/Transfer Host


  Harbors parasites that do not develop to further stages, only transfers from one host to another
• Dead-end Host/Incidental Host


  Host that does not anymore allow the life cycle of the parasite to continue
• Reservoir Host


  Host other than the parasite's usual hosts that allows the life cycle to continue, becomes additional sources of human infection
• Obligate Parasite


  Parasite that always requires a host to survive, most parasites
• Facultative Parasite


  Has a free-living and parasitic phase
• Commensal Parasite


  Non-pathogenic, does not cause disease
• Parasites According to Habitat

  • Ectoparasite (parasite lives outside the host)
  • Endoparasite (parasite lives inside the host)
  • Erratic Parasite (parasite not living in its natural habitat)
  • Accidental/Incidental Parasite (parasite that does not live in its usual host)
  • Spurious Parasite (free-living organism that passes through the GI tract without infecting the host)
• Parasites According to Duration

  • Temporary/Transient (parasite)
  • Permanent (parasite remains on host for its entire life)
• Parasites According to Egg Laying Capacity

  • Oviparous (lays immature eggs)
  • Ovoviviparous (lays mature eggs)
  • Larviparous (larva-laying)
• Parasites According to Sexes

  • Monoecious/Hermaphrodites (both testes and ovaries found in one parasite)
  • Dioecious (presence of separate sexes, female and male parasite)
  • Parthenogenetic (females capable of self-fertilization)
• Parasite Stages


  • Adult (mature form)
  • Larva (immature form, stages include L1-L3)
  • Egg/Ovum (nonmotile, resistant, infective stage)
• Protozoan Parasite Stages


  • Trophozoite (motile/vegetative stage)
  • Cyst (nonmotile, usually the infective stage)
• Transmission Routes


  • Soil Transmitted Helminths (HATS)
  • Vector Borne (mosquitoes and ticks)
  • Food Borne (undercooked or raw food)
  • Water Borne (drinking contaminated water)
  • Vertical Transmission (congenital)
  • Transmammary (drinking of breast milk)
  • Skin Penetration (exposure of skin to soil or water)
  • Inhalation (of airborne eggs)
  • Intimate Contact (sexual contact)
• Life cycles can be direct (no intermediate host) or indirect (has an intermediate host)
• Life cycle more complicated = lesser chances for parasite to survive
• Disease


  Presence of signs and symptoms
• Pathogen


  Any organism that causes disease
• Infection


  Establishment of an organism in one host (with multiplication of organism), no destruction of tissue yet
• Carrier


  Harbors the organism, but person shows no signs or symptoms
• Incubation Period


  Period between infection and appearance of signs and symptoms, no symptoms in this period
• Pre-patent Period


  Period between infection and evidence/demonstration of infection, positive lab result, can be ahead of incubation period, or lesser
• Exposure


  Process of inoculating an infective agent
• Autoinfection


  Infected individual becomes his/her own source of infection, parasite does not need to go outside body to replicate/multiply
• Superinfection/Hyperinfection


  Infected individual is further infected with the same parasite
• Epidemiology


  Study of patterns, distribution, and occurrence of disease
• Prevalence


  Number of patients infected at one point in time
• Cumulative Prevalence


  Percentage of individuals in a population infected with at least one parasite