INTRODUCTION-TO-PARASITOLOGY

INTRODUCTION TO PARASITOLOGY

Presented By:

  • Jenalyn D. Bontipula

  • Kylla B. Espiamba

  • BSN 2-A

LEARNING OBJECTIVES

By the end of this chapter, students will be able to:

  1. Define "symbiosis"

  2. Enumerate different types of symbiotic relationships with examples

  3. Classify various forms of parasites and hosts

  4. Identify various sources of parasitic infections with examples

  5. Enumerate modes of transmission of parasites, providing examples

  6. Discuss mechanisms by which parasites cause diseases in humans

  7. Describe proper specimen collection and handling for laboratory diagnosis

  8. Compare different laboratory diagnostics procedures for parasitic infections

  9. Illustrate taxonomic classification of parasites

SYMBIOSIS

  • Defined as a relationship where unlike organisms exist together.

  • Types of symbiotic relationships:

    • Commensalism: One species benefits without affecting the other.

    • Mutualism: Both organisms benefit from the relationship.

    • Parasitism: One party (the parasite) benefits at the expense of the other (the host).

PARASITISM

  • Involves two key elements: the parasite and the host.

  • Parasites depend on the host for survival and can be classified in various ways:

    1. Based on Habitat:

      • Ectoparasites: Live outside the host (e.g., fleas, lice). Infestation occurs.

      • Endoparasites: Live inside the host body (e.g., helminths). Infection results from entry and multiplication in the host.

    2. Based on Ability to Live Independently of Host:

      • Facultative Parasites: Can live independently (free-living).

      • Obligate Parasites: Must live in a host (e.g., Plasmodium). Most human-infecting parasites are obligate.

    3. Based on Mode of Living:

      • Permanent Parasites: Reside in host throughout maturity (e.g., Plasmodium).

      • Intermittent Parasites: Visit hosts for feeding (non-pathogenic).

      • Incidental Parasites: Found in unusual hosts (e.g., dog tapeworm in humans).

      • Transitory Parasites: Larvae develop in a host; adult is free-living (e.g., Echinococcus granulosus).

    4. Erratic Parasites: Locate in unusual organs (e.g., Ascaris lumbricoides in lungs).

TYPES OF HOSTS

  1. Definitive Hosts: Harbor the adult or sexual stage of the parasite (e.g., mosquito for malaria).

  2. Intermediate Hosts: Harbor the larval or asexual stage.

  3. Reservoir Hosts: Vertebrates that harbor the parasite, acting as a source for humans.

  4. Paratenic Hosts: Transport parasites to the final host.

SOURCES OF PARASITIC INFECTION

  • Contaminated Soil or Water

  • Food containing the parasite’s infective stage

  • Blood-sucking Insects

  • Animals harboring the parasite

  • Other humans and contaminated environments

  • Auto-infection by oneself

MODES OF TRANSMISSION

  • Ingestion: Through contaminated food/water (fecal-oral).

  • Skin Penetration: Direct entry (e.g., hookworms).

  • Insect Bites: Vectors for diseases (e.g., malaria).

  • Other Routes:

    • Inhalation (pinworm).

    • Transplacental (e.g., Toxoplasma).

    • Transmammary (mother's milk).

    • Sexual Intercourse (Trichomonas vaginalis).

PORTALS OF EXIT

  • Primary portal: Anus (for fecal parasites)

  • Other portals:

    • Urine: For specific parasites (T. vaginalis, Strongyloides).

    • Sputum: For lung fluke and intestinal roundworm.

    • Vaginal discharge: For sexual transmission.

MECHANISMS OF DISEASE PRODUCTION

  • Pathogenesis: The disease process dynamics.

  • Parasite damage mechanisms:

    1. Trauma or Physical Damage

    2. Lytic Necrosis: Caused by enzymes (e.g., Entamoeba histolytica).

    3. Stimulation of Host Tissue Reaction: Increased eosinophils in helminth infections.

    4. Toxic and Allergic Reactions: Antibody responses can lead to hypersensitivity.

LIFE CYCLE OF PARASITES

  • Involves various important components:

    1. Source of Infection

    2. Mode of Transmission

    3. Infective Stage

    4. Pathogenic Stage

    5. Diagnostic Stage

CLASSIFICATION OF PARASITES

  • Protozoa (single-celled)

  • Helminths (multicellular, divided into Nemathelminthes (roundworms) and Platyhelminthes (flatworms)).

  • Parasitic protozoa classified by locomotion and reproduction (amoebae, flagellates, sporozoa, ciliates).

LABORATORY DIAGNOSIS

Specimen Collection, Handling, and Transport

  • Proper procedures are critical for management.

  • Stool samples are commonly collected; multiple specimens may be necessary for accurate diagnosis.

Microscopic Examination

  • Involves direct wet preparations, concentration techniques, and permanent stains for parasite identification.

Concentration Techniques

  • Sedimentation: Heavier parasites settle at the bottom of the test tube.

  • Flotation: Lighter parasites float to the top; may not detect some helminth eggs.

Permanent Stains

  • Final step for confirming presence of protozoan cysts and/or trophozoites.

OTHER SPECIMEN AND LABORATORY PROCEDURES

  • Various specimens for the detection of parasites include:

    • Duodenal Fluid: Via nasogastric tube or Entero-test.

    • Sigmoidoscopy: Colon material for Entamoeba histolytica diagnosis.

    • Cellophane Tape Preparation: To detect pinworm eggs.

    • Blood: For blood-borne parasites.

    • CSF: For amoebic infections and African sleeping sickness.

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