Parasitology Review Flashcards

Introduction to Parasitology

• Definition of Parasites: Organisms that derive nutrients from a host and cause harm in the process.

• Medical Parasitology: Study of pathogenic protozoa and helminths (worms) impacting humans and animals.

Protozoa

• Characteristics:

  • Single-celled eukaryotic organisms, part of Domain Eukarya, Kingdom Protista.

  • Majority are nonpathogenic; few species cause disease.

• Structure:

  • All protozoa have a nucleus, cytoplasm, plasma membrane, and eukaryotic organelles.

  • Some possess a protective covering called a pellicle.

  • Feeding form is the trophozoite, while the dormant stage is the cyst (protective encapsulation).

• Lifecycle Importance:

  • Cysts allow protozoa to survive unfavorable conditions and facilitate transmission between hosts.

Major Groups of Protozoa

1. Sarcodina (Amoebae):

   • Move by pseudopods (extensions of cytoplasm).

2. Mastigophora (Flagellates):

   • Move with flagella (whip-like tails).

3. Ciliata (Ciliates):

   • Move with cilia (hair-like structures).

4. Sporozoa (Apicomplexa):

   • Non-motile, obligate intracellular parasites.

Transmission and Diagnosis

• Transmission may occur via contaminated food/water, or through arthropod vectors.

• Diagnosis based on the identification of characteristic structures in specimens (e.g. feces, blood).

Representative Pathogenic Protozoa (Table 1)

• Amebiasis (Dysentery):

  • Type: Amoeba

  • Organism: Entamoeba histolytica

  • Transmission: Fecally contaminated water

  • Diagnosis: Fresh stool

• Giardiasis:

  • Type: Flagellate

  • Organism: Giardia lamblia

  • Diagnosis: Fresh stool

• Trichomoniasis:

  • Type: Flagellate

  • Organism: Trichomonas vaginalis

  • Diagnosis: Vaginal discharge

• Trypanosomiasis:

  • Type: Flagellate

  • Organisms: Trypanosoma gambiense, Trypanosoma rhodesiense, Trypanosoma cruzi

  • Diagnosis: Blood smear

• Malaria:

  • Type: Sporozoa

  • Organism: Plasmodium

  • Diagnosis: Blood smear

Helminths

• Characteristics:

  • Multicellular organisms, sizes ranging from millimeters to several meters.

  • Can be hermaphroditic or have separate sexes.

• Lifecycle:

  • Eggs can be infective for humans and develop into larval forms within the host.

Major Groups of Helminths

1. Platyhelminths (Flatworms):

   • Trematodes (Flukes): Leaf-shaped bodies with suckers, site-specific adult living conditions. Transmission may occur through skin penetration or ingestion.

   • Cestodes (Tapeworms): Attach to the intestinal mucosa, segmented body filled with eggs (proglottids).

2. Nematodes (Roundworms):

   • Cylindrical, complete digestive tract, usually separate sexes. May acquire infection through eggs or larvae.

Representative Parasitic Helminths (Tables 2 & 3)

• Table 2: Platyhelminths:

  • Schistosomiasis:

  • Type: Trematode

  • Organism: Schistosoma mansoni, Schistosoma japonicum, Schistosoma haematobium

  • Transmission: Skin contact with cercariae

  • Diagnosis: Ova in feces, urine.

• Table 3: Nematodes:

  • Ascariasis:

  • Organism: Ascaris lumbricoides

  • Transmission: Ingestion of eggs from contaminated soil.

  • Diagnosis: Ova in feces.

• Pinworm Disease:

  • Organism: Enterobius vermicularis

  • Diagnosis: Ova from perianal region using Scotch tape.

Laboratory Observations (Materials Section)

• Prepared slides needed for observing protozoa and helminths.

Practice Questions and Assignment Highlights

1. Classify the four major groups of protozoa.

2. Identify amoebic dysentery's causative agent and its group.

3. Describe transmission methods of protozoa and diagnostic techniques.

4. Distinguish features and diagnosis of flatworms and roundworms.

5. Understanding symptoms, sources of infection, and prevention of infections like malaria, trichinosis, and helminth infestations.