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Questions and Answers
What is the definition of a parasite?
What is the definition of a parasite?
A living organism that acquires its basic requirements and derives all benefits through intimate contact with another organism (partner), causing harm to the "partner" (host).
What are the two main types of parasites based on their location in the host's body?
What are the two main types of parasites based on their location in the host's body?
Match the following terms with their definitions:
Match the following terms with their definitions:
Ectoparasite = Parasite that lives outside the body of the host Endoparasite = Parasite that lives inside the body of the host Definitive host = Host in which the parasite reaches sexual maturity, or the most important host if no reproduction occurs. Intermediate host = Host in which the parasite undergoes some development or asexual reproduction but not sexual maturity.
What is the most important host for Schistosoma mansoni?
What is the most important host for Schistosoma mansoni?
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A snail is an intermediate host for Toxoplasma gondii.
A snail is an intermediate host for Toxoplasma gondii.
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Which parasite is considered the only ciliate protozoan parasite of humans and is also the largest protozoan?
Which parasite is considered the only ciliate protozoan parasite of humans and is also the largest protozoan?
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Which phylum of protozoa are obligate parasites and exhibit gliding motility?
Which phylum of protozoa are obligate parasites and exhibit gliding motility?
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What is the scientific name of the parasite that causes amoebiasis?
What is the scientific name of the parasite that causes amoebiasis?
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What causes giardiasis in humans?
What causes giardiasis in humans?
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What are the two types of life cycles in protozoa?
What are the two types of life cycles in protozoa?
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What type of organism is Balantidium coli?
What type of organism is Balantidium coli?
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What type of reproduction occurs in ciliates?
What type of reproduction occurs in ciliates?
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Which of the following are examples of Apicomplexa parasites?
Which of the following are examples of Apicomplexa parasites?
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Which of the following are examples of flatworms?
Which of the following are examples of flatworms?
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What is the name of the largest nematode parasitizing the human intestine?
What is the name of the largest nematode parasitizing the human intestine?
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Which of the following are types of hookworms that infect humans?
Which of the following are types of hookworms that infect humans?
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Which filarial worm is responsible for 90% of lymphatic filariasis cases?
Which filarial worm is responsible for 90% of lymphatic filariasis cases?
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Which type of worm is usually acquired in childhood and causes hidden damage to the lymphatic system?
Which type of worm is usually acquired in childhood and causes hidden damage to the lymphatic system?
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What are the characteristic structures of a nematode?
What are the characteristic structures of a nematode?
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What is the name of the disease caused by Ascaris lumbricoides?
What is the name of the disease caused by Ascaris lumbricoides?
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What is the name of the disease caused by Balantidium coli?
What is the name of the disease caused by Balantidium coli?
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How many stages does the life cycle of Ascaris lumbricoides have?
How many stages does the life cycle of Ascaris lumbricoides have?
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Unfertilized eggs of Ascaris lumbricoides are infective.
Unfertilized eggs of Ascaris lumbricoides are infective.
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What is the main mode of transmission for hookworms?
What is the main mode of transmission for hookworms?
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Why are hookworms referred to as bloodsuckers?
Why are hookworms referred to as bloodsuckers?
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What is another name for lymphatic filariasis?
What is another name for lymphatic filariasis?
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What is the name of the infective stage of Wuchereria bancrofti?
What is the name of the infective stage of Wuchereria bancrofti?
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Which of the following are unique characteristics of tapeworms?
Which of the following are unique characteristics of tapeworms?
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What is the name of the head of a tapeworm?
What is the name of the head of a tapeworm?
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What are the segments of a tapeworm called?
What are the segments of a tapeworm called?
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All flukes (trematodes) are hermaphroditic.
All flukes (trematodes) are hermaphroditic.
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What is the name of the fluke that lives in the liver and can cause fascioliasis?
What is the name of the fluke that lives in the liver and can cause fascioliasis?
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The life cycle of Plasmodium involves only one host.
The life cycle of Plasmodium involves only one host.
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What is the name of the type of mosquito that transmits malaria to humans?
What is the name of the type of mosquito that transmits malaria to humans?
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What is the name of the infective stage of Plasmodium that is injected into humans by mosquitoes?
What is the name of the infective stage of Plasmodium that is injected into humans by mosquitoes?
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Study Notes
Introduction to Parasitology
- Course presenter: Chuah Candy (Ph.D.)
- Affiliation: Unit of Microbiology, Faculty of Medicine, AIMST University
Topic Outcomes
- Define terms related to parasitology
- Describe parasite classification
- Discuss transmission of medically important parasites
- Discuss life cycles of important parasites (Entamoeba, Giardia, Plasmodium, Ascaris, Ancylostoma, filarial worms)
- Apply knowledge of life cycles to laboratory diagnosis
Parasites
- An organism that acquires its needs through intimate contact with another organism (host), causing harm to the host
- Possess special structures/features: adult, developmental stages
- Classification based on:
- Physical characteristics
- Morphology
- Phylogenetics
- Location of infestation
Terminology
Ectoparasite
- Parasite residing outside the host's body
- Example: Lice on human scalp
Endoparasite
- Parasite residing inside the host's body
- Example: Ascaris lumbricoides in human intestines
Definitive host
- Host in which the parasite reaches sexual maturity, or the most important host if no reproduction occurs
- Example: Human is the definitive host for Schistosoma mansoni
Intermediate host
- Host in which the parasite undergoes development or asexual reproduction, but not sexual maturity
- Example: Snail is an intermediate host for Schistosoma mansoni, and mice/birds are intermediate hosts for T. gondii
Schistosoma spp. Life Cycle
- Diagram showing the life cycle stages, including free-swimming cercariae, snail tissue penetration, human skin penetration, circulation, migration to portal blood, development into adults, and migration to the mesenteric venules/blood vessels.
- Diagnostic and infective stages are marked in the diagram
Classification of Parasites
- Classifies parasites into Protozoa, Helminths, and Ectoparasites.
- Protozoa further divided into Intestinal, Urogenital, Blood & Tissue
- Helminths further divided based on Nematode, Cestode, Trematode
- Ectoparasites further classified with examples of Ticks, Fleas, Lice, Mites
Protozoa
General Characteristics
- Microscopic, unicellular eukaryotes
- Perform complex metabolic processes, including respiration, excretion, and digestion
- Most are free-living; some are parasitic
Morphology
- Most medically important protozoa are <50 µm
- Each cell has a nucleus (with a karyosome) and cytoplasm
- Cytoplasm divided into ectoplasm (outer, transparent layer) and endoplasm (inner, granular layer)
- Ectoplasm: Protection, locomotion, and sensation
- Endoplasm: Nutrition and reproduction
Stages
- Cyst: A resting stage that allows the parasite to survive in unfavorable conditions
- Trophozoite: The active feeding and growing stage of the parasite
Life Cycle
-
Direct: One host
-
Indirect: Two or more hosts
-
Example diseases for direct life cycle: Ascariasis, Giardiasis, Trichuriasis
-
Example diseases for indirect life cycle: Malaria, Schistosomiasis, Taeniasis
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Diagram showing direct life cycle of A. lumbricoides
-
Diagram showing indirect life cycle of Plasmodium
Reproduction
- Asexual reproduction:
- Binary fission
- Schizogony
- Sexual reproduction:
- Sporogony
- Conjugation
Classification of medically important Protozoa
- Diagram showing a hierarchy of Protozoa of medical importance by Phylum
Phylum Sarcomastigophora
- Movement: Pseudopodia (Amoeba), flagella (Flagellates)
- Asexual reproduction common
- Includes: Entamoeba histolytica (intestinal amoeba), Giardia lamblia (intestinal flagellate), Leishmania (tissue flagellate), Trypanosoma (tissue flagellate)
Subphylum Sarcodina (Amoeba)
- Movement: Pseudopodia
- Includes: Entamoeba, Endolimax, Iodamoeba, Naegleria, Acanthamoeba
Entamoeba histolytica
- Third leading cause of death in developing countries due to amoebiasis
- Pathogenic amoeba associated with intestinal and extraintestional infections (liver, brain, lungs)
- Risk factors: Contaminated food/water, contaminated hands of food handlers
- Trophozoites found in large intestine: lumen, mucosa, submucosa
- Diagram showing morphology of Trophozoite form and Cyst form of E. histolytica
- Diagram showing life cycle of amoebiasis
Giardia lamblia
- Causes giardiasis, primarily in young children and is transmitted by ingestion of cysts in contaminated water/food
- Inhabits small intestine, mainly in duodenum, jejunum, upper ileum
- Has trophozoites and cysts forms
- Diagrams showing morphology of Cysts and Trophozoites of Giardia lamblia
- Diagram showing life cycle of giardiasis
Phylum Ciliophora (Ciliates)
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Movement: Cilia
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Includes: Paramecium spp., Vorticella spp., Balantidium coli (only human pathogen in this phylum)
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Balantidium coli*
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The only ciliated protozoan parasite of humans
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Found in large intestine
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Causes balantidiasis
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Morphology: Trophozoite and Cyst form
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Diagrams available for morphology
Plasmodium spp.
- Etiologic agents: P. falciparum, P. vivax, P. ovale, P. malariae, P. knowlesi
- Transmitted by female Anopheles mosquitoes
- Causes malaria, most important tropical disease
- Morphological forms: Sporozoites, Ring, Trophozoites, Schizont, merozoites, gametocytes
- Diagrams of various stages available
- Diagram showing life cycle stages, including mosquito and human stages
Helminths
-
Nematoda (Roundworms):
- Ascaris lumbricoides (most prevalent), Trichuris trichiura, Ancylostoma duodenale, Necator americanus, Strongyloides stercoralis, Enterobius vermicularis
- Classification diagrams with location/habitat and specific examples from different categories (Nematoda, Cestoda and Trematoda)
- Unique characteristics of each Class are provided, with examples
Hookworms
- Ancylostoma duodenale, Necator americanus
- Hookworms are bloodsuckers
- Infect by larvae penetrating skin from soil
- Diagram illustrating life cycle
Filarial Worms
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Caused by three species of nematodes (Wuchereria bancrofti, Brugia malayi, Brugia timori)
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Cause lymphatic filariasis, also known as elephantiasis
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Transmission through mosquitoes
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Diagram illustrating life cycle
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