L1 : Intro to Para

• Medical Parasitology deals with the parasites, which cause human infections and the diseases they produce
• Medical Parasitology is divided into 2 parts : Protozoology & Helminthology
• Parasite-Host Relationships :

  1. Symbiosis
  2. Commensalism
  3. Mutualism
  4. Parasitism
• Parasite-Host Relationship (Symbiosis) - living together of unlike organisms. It may also involve protection or other advantages to one or both organisms
• Parasite-Host Relationship (Commensalism) - symbiotic relationship in which two species live together and one species benefits from the relationship without harming or benefiting the other
• Parasite-Host Relationship (Mutualism) - Symbiosis in which two organisms mutually benefit from each other
• Parasite-Host Relationship (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
• Types of Parasites :

  1. Obligatory Parasite
  2. Facultative Parasite
  3. Endoparasite
  4. Ectoparasite
• Obligatory Parasite - Parasite that cannot survive ourside 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
• Types of Host

  1. Accidental or Incidental Host
  2. Definitive Host
  3. Intermediate Host
  4. Reservoir Host
  5. Transport Host
  6. Carrier
• 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 larval asexual phase of parasite development occurs
• Reservoir Host - Host harboring parasites that are parasitic for humans and from which humans may become infected
• Carrier - Parasite-harboring host that is not exhibiting any clinical symptoms but can infect others
• Transport Host - Host responsible for transferring a parasite from one location to another
• Parasitic life cycle components :

  1. Mode of transmission
  2. Infective stage
  3. Diagnostic stage
• Direct life cycle - when a parasite requires only single host to complete its development (? → source → host → adult)
• Indirect life cycle - when a parasite requires 2 or more species of host to complete its development (? → source → host 1 (animal vectors - intermediate host) → host2 (humans) → adult)
• Sources of infection :

  1. Contaminated soil and water
  2. Food
  3. Insect vectors
  4. Animals
  5. Other persons
• Insect vectors - an agent usually an arthropod that transmits an infection from man to man of from other animals to man
• Modes of transmission :

  1. Oral transmission
  2. Skin transmission
  3. Vector transmission
• Oral transmission - oral route by contaminated food, water, soiled fingers, or formites. 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
• Modes of infection :

  1. Direct Transmission
  2. Vertical Transmission
  3. Iatrogenic Transmission
• 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
• A parasitic disease may affect the entire body or any of its parts the major body areas associated wuth such processes include the following :

  1. Gastrointestinal (GI) and urogenital (UG) tracts
  2. Blood and tissue : Anemia
  3. Liver, lung, and other major organs
  4. Miscellaneous locations -cerebrospinal fluid (CSF), eye, skin, and extremities
• Preventions and control :

  1. Morbidity control
  2. Environmental Management
  3. Environmental Sanitation
• 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