Parasitology Midterms

• Medical Parasitology


  It deals with the parasites, which cause human infections and the diseases they produce
• Medical parasitology


  Divided into Protozoology and Helminthology
• Symbiosis


  Parasite-host relationship where unlike organisms live together. It may also involve protection or other advantages to one or both organisms
• Commensalism


  Symbiotic relationship in which two species live together and one species benefits from the relationship without harming or benefiting the other
• Mutualism


  Symbiosis in which two organisms mutually benefit from each other
• Parasitism


  Symbiotic relationship where one organism, the parasite, lives in or on another, depending on the latter for its survival and usually at the expense of the host
• Obligatory Parasite


  Parasite that cannot survive outside the host
• Facultative Parasite


  Parasite that is capable of existing independently of a host
• Endoparasite


  Parasite that is established inside of a host
• Ectoparasite


  Parasite that is established in or on the exterior / surface of a host
• Accidental or Incidental Host


  Hosts that have been infected by parasite, but the parasite is not commonly seen in the organism/human
• 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 parasitic for humans and from which humans may become infected
• Transport Host


  Host responsible for transferring a parasite from one location to another
• Carrier


  Parasite-harboring host that is not exhibiting any clinical symptoms but can infect others
• Common components of parasitic life cycles

  • Mode of transmission
  • Infective stage
  • Diagnostic Stage
• Direct Life Cycle


  When a parasite requires only a single host to complete its developments
• Indirect Life Cycle


  When a parasite requires 2 or more species of host to complete its development
• Sources of Infection


  • Contaminated soil and water
  • Food
  • Insect vectors
  • Animals
  • Other persons
• Insect vectors


  An agent, usually an arthropod that transmits an infection from man to man or from other animals to man
• Oral Transmission


  Contaminated food, water, soiled fingers, or fomites. Majority of infections with cestodes, trematodes, and intestinal protozoans are food borne
• Skin Transmission


  Hookworms and strongyloidiasis enter via exposure of skin to soil, while Schistosoma species enter skin via water
• Vector Transmission


  Transmission through insect bite
• Direct Transmission


  Parasitic infection may be transmitted by person-to-person contact in some cases
• Vertical Transmission


  Mother to fetus transmission
• Iatrogenic Transmission


  See in case of blood transfusion, malaria, and toxoplasmosis after organ transplantation
• Disease Processes and Symptoms

  • Gastrointestinal (GI) and urogenital (UG) tracts
  • Blood and tissue: Anemia
  • Liver, lung, and other major organs
  • Miscellaneous locations- cerebrospinal fluid (CSF), eye, skin, and extremities
• Morbidity Control


  Avoidance of illness cause by infections. It may be achieved by periodically deworming individuals or groups, known to be at risk of morbidity
• Environmental Management


  The planning, organization, performance, and monitoring of activities for the modification and/or manipulation of environmental factors or their interactions with human beings with a view to preventing or minimizing vector or intermediate host propagation and reducing contact between humans and the infective agent
• Environmental Sanitation


  Interventions to reduce environmental health risks including the safe disposal and hygienic management of human and animal excreta, refuse, and wastewater
• Nematodes


  Most worm-like of all helminths, resemble the common earthworm in appearance, is elongated, cylindrical, unsegmented worms with tapering ends
• Nematode


  Means thread-like
• Nema


  Means thread
• Nematodes Lifecycle


  • Ova Egg
  • Larval Stage
  • Adult Formation
• Ascaris Lumbricoides


  Common Names: Large intestinal roundworm, roundworm of man; Causes: Ascariasis, roundworm infection; A soil-transmitted helminth
• Ascariasis


  Considered as the most common intestinal helminth infection in the world
• Trichuris Trichiura


  Common name: Whipworm; Causes: Trichuriasis or whipworm infection
• Hookworms


  Refers to two organisms: 1. Ancylostoma duodenale 2. Necator americanus; Soil-transmitted helminths; Blood-sucking nematodes that attach to the mucosa of the small intestines
• Necator americanus


  Common name: New World hookworm; Causes: Hookworm infection, necotoriasis