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Questions and Answers
What is the definition of a parasite?
What is the study of parasites called?
What type of parasite can live freely or as a parasite?
What is the term for a host that harbors the adult or final stages of a parasite?
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What is the term for a host that harbors the larval stages of a parasite?
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What type of relationship exists between two organisms when one benefits and the other is not affected?
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What is the term for a permanent association between two organisms?
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What is the term for a host that tolerates a parasite and serves as a source of infection for other organisms?
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What is the term used to describe the relationship when one organism benefits and the other is harmed?
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What is the term used to describe diseases that can be transmitted from animals to humans?
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What is the name of the disease caused by Entamoeba histolytica?
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What is the mode of locomotion of Entamoeba histolytica?
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Where is Entamoeba histolytica typically found?
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What is the infective stage of Entamoeba histolytica?
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How does Entamoeba histolytica typically infect humans?
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What is the major reservoir of Entamoeba histolytica?
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What is the primary mode of transmission of Plasmodium to humans?
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What is the incubation period of Plasmodium in the human liver?
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What is the result of infected red cells obstructing blood vessels in the brain?
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What is the name of the disease caused by Toxoplasma infection?
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How does Plasmodium develop in the mosquito?
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What is the primary mode of transmission of Toxoplasma to humans?
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What is the result of Plasmodium infection in immunocompromised individuals?
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What is the result of congenital Toxoplasma infection?
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What is the primary mode of transmission of tapeworms to humans?
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What is the typical duration between initial exposure and the onset of the intestinal phase?
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What is the primary habitat of adult tapeworms?
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What is the typical length of a nematode?
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What is the name of the disease caused by tapeworm infection?
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What percentage of the world population is infected with Ascaris lumbricoides?
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What is the usual length of an adult tapeworm?
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Where do the larvae of Ascaris lumbricoides penetrate after being ingested?
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Where do the larval forms of the tapeworm typically lodge?
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How many eggs can a female Ascaris lumbricoides produce per day?
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What is the name of the intermediate host of the tapeworm?
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What is the duration of the lung phase of Ascaris lumbricoides?
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What is a common symptom of high-level tapeworm infection?
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What is the effect of having large numbers of adult worms in the intestine?
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What is the duration of the life cycle of Ascaris lumbricoides from egg to mature adult?
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What is the condition caused by Ascaris lumbricoides in the lung?
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Study Notes
Parasitology
- Parasitology is the study of parasites, which are organisms that live temporarily or permanently in or on another organism.
- There are three types of parasites:
- Facultative parasites: able to live both free-living and as parasites.
- Obligate parasites: parasite living permanently in a host and cannot live without a host (e.g., Trichomonos species).
- Coprozic (spurious) parasites: foreign organisms that pass through the alimentary canal without causing any harm.
Clinical Parasitology
- Deals with animal parasites of man and their medical importance.
- Divisions of Parasitology:
- Protozoa
- Helminthes
- Roundworms (nematodes)
- Flatworms – Cestodes (tapeworm)
- Trematodes (flukes)
Parasitism
- One organism depending on another for living, where one is living at the expense of the other and is harmful.
- The organism being harmed is called the Host.
- Classification of Hosts:
- Definitive host: harbors the adults or final stages or sexual stages (e.g., man).
- Intermediate host: harbors the larva stages or intermediate stages in the development (e.g., cattle).
- Reservoir host (carrier): the carrier host is well adapted to the parasite and tolerates the infection, but serves as a source of infection to other organisms.
Relationships between Organisms
- Symbiosis: a permanent association between two organisms.
- Mutualism: two organisms living together, where both benefit.
- Commensalism: two organisms living together, where one benefits and the other is not affected.
- When the other organism becomes affected, the relationship turns into parasitism.
Zoonosis
- A disease of animals that can be transmitted to humans.
- Example: Hymenolepis nana.
Protozoa
- Intestinal protozoa:
- Entamoeba histolytica
- Giardia lamblia
- Cryptosporidium
- Blood and tissue protozoa:
- Malaria
- Toxoplasma
- Trypanosoma
- Urogenital tract protozoa:
- Trichimonas Vaginalis
- Leishmaina
Entamoeba histolytica
- Disease: Amoebiasis
- Mode of locomotion: Pseudopodia (false feet)
- Geographic distribution: cosmopolitan, but more common in tropical and subtropical countries and in countries with poor sanitation.
- Habitat: in the lumen of the large intestine (it is pathogenic because it can invade the wall of the intestine).
- Reservoir: major: humans, minor: dogs, pigs, monkeys
- Morphology: 2 forms - Cyst and Trophozoite
- Infective stage: in polluted water and in infected food.
- Pathogenic stage: gives pathology as a result of infection.
Plasmodium
- Disease: Malaria
- Transmission: through the bite of an infected mosquito.
- Development: in the gut of the mosquito and is passed on in the saliva of an infected insect.
- In the human body, it develops in the liver and then in the red blood cells, causing bouts of fever and anemia.
Toxoplasma
- Disease: Toxoplasmosis
- Geographic distribution: worldwide
- Transmission:
- Eating raw or undercooked meat of sheep and cows containing viable trophozoites.
- Swallowing food and water contaminated with infected cat feces.
- Congenital transmission, through the placenta (fatal).
- Person-to-person transmission, through blood transfusion or organ transmission.
- Clinical symptoms:
- Infection of normal human hosts is common and usually asymptomatic.
- Infection can be severe in immunocompromised individuals.
- Congenital infections can be severe and are the major cause of blindness in newborns.
Helminthes
- Nematodes:
- Definition: a division of eukaryotic parasites that live inside their host.
- Characteristics: worm-like, live and feed off living hosts, receiving nourishment and protection while disrupting their hosts' nutrient absorption, causing weakness and disease.
- Ascaris lumbricoides:
- Definition: the largest nematode (roundworm) parasitizing the human intestine.
- Geographic distribution: worldwide, common among people with low standard of living and among children.
- Morphology:
- Adult: in small intestine.
- Egg: infective stage.
- Clinical symptoms:
- Related to the number of worms.
- Small numbers: asymptomatic.
- Large numbers: obstruction, pains, and malnutrition.
Tapeworms
- Definition: ribbon-shaped, multi-segmented flatworms that dwell as adults entirely in the human small intestine.
- Habitat: the small intestine—the ileum.
- Transmission: acquired in humans through the ingestion of raw or poorly cooked meat of infected cows.
- Morphology:
- Adult: divided into three parts - head, neck, and number of segments.
- Egg: present in feces.
- Clinical symptoms:
- High infection: diarrhea and constipation.
- Vomiting.
- Loss of appetite.
- Anemia.
Trematodes
- Definition: flattened, oval or worm-like animals, usually no more than a few centimeters in length.
- Characteristics: distinctive external feature is the presence of two suckers, one close to the mouth and the other on the underside of the animal.
- Habitat: adult in small intestine of man only, egg in feces, and larva stage in muscle of cattle only (intermediate host).
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Description
Learn about parasites and their characteristics. Identify the different types of parasites, including facultative and obligate parasites. Understand the study of parasites, known as parasitology.
