Basic Transmission & Prevention of Parasitic Diseases

A) Basic factors of transmission of parasitic diseases:
1) The source of the infection
2) The routes of transmission
3) The susceptible host

         Parasitic disease → Infectious disease → Transmission

The combined effect of those factors, helps in:
1. Determine the spread and the prevalence of the parasites at a given time and place
2. Regulate the incidence of the parasitic diseases in certain local population

The source of the infection
1. Patient (Case): Persons who have parasites in their body and show clinical symptoms
2. Carrier: Persons who have parasites in their body but not show clinical symptoms
3. Reservoir host: Animals that harbors the same species of parasites as man. Sometimes, the parasites in the animals can be transmitted to human

The routes of transmission 
1. Congenital transmission: From mother to infant, toxoplasmosis
2. Contact transmission: 
    - Direct contact - Trichomonas vaginalis
    - Indirect contact - Ascaris lumbricodes
3. Food transmission: The infectious stage of parasites contaminated food/The meat of intermediate host containing infectious stage of parasites
4. Water transmission: Drink or contact the water contaminated the infectious stage of parasites
5. Soil transmission: Contamination of the soil by feces containing the certain stage of parasites and this stage can develop into another stage
6. Arthropod transmission: vectors of certain parasitic diseases

The susceptible host
In general, most people is the susceptible host. The parasite reaching the susceptible host must gain entrance and set up a favorable residence in order to complete its life cycle and cause the transmission of parasitic diseases

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B) The avenue of invasion:
1) Digestive tract: Most common avenue of entrance
    (food/water transmission)
2) Skin: Infective larvae perforate skin and reach to body and establish infection
    (soil/water transmission)
3) Blood: Bloodsucking insects containing infective parasites bite the skin and inject parasites into human blood
    (Arthropod transmission → Malaria)

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C) The prevention measures of the parasitic diseases:
1) Controlling the source of infection:
    - Treatment of the patients, carriers and reservoir hosts
2) Intervention at the routes of transmission:
    - Managing feces and water resource
    - Controlling or eliminating vectors and intermediate hosts
3) Protecting the susceptible hosts:
    - Paying attention to personal hygiene
    - Changing bad eating habit
    - Taking medicine

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