Parasitology Fundamentals

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Questions and Answers

What is the definition of a parasite?

An organism that provides food and shelter to another organism.

An organism that harms another organism intentionally.

An organism that lives in or on another organism, temporarily or permanently. (correct)

An organism that is benefited by the presence of another organism.

What is the study of parasites called?

Parasitology (correct)

Mutualism

Symbiosis

Commensalism

What type of parasite can live freely or as a parasite?

Obligate parasite

Facultative parasite (correct)

Helminth

Coprozic parasite

What is the term for a host that harbors the adult or final stages of a parasite?

Definitive host Signup and view all the answers

What is the term for a host that harbors the larval stages of a parasite?

Intermediate host Signup and view all the answers

What type of relationship exists between two organisms when one benefits and the other is not affected?

Commensalism Signup and view all the answers

What is the term for a permanent association between two organisms?

Symbiosis Signup and view all the answers

What is the term for a host that tolerates a parasite and serves as a source of infection for other organisms?

Reservoir host Signup and view all the answers

What is the term used to describe the relationship when one organism benefits and the other is harmed?

Parasitism Signup and view all the answers

What is the term used to describe diseases that can be transmitted from animals to humans?

Zoonosis Signup and view all the answers

What is the name of the disease caused by Entamoeba histolytica?

Amoebiasis Signup and view all the answers

What is the mode of locomotion of Entamoeba histolytica?

Pseudopodia Signup and view all the answers

Where is Entamoeba histolytica typically found?

Large intestine Signup and view all the answers

What is the infective stage of Entamoeba histolytica?

Cyst Signup and view all the answers

How does Entamoeba histolytica typically infect humans?

Through contaminated water or food Signup and view all the answers

What is the major reservoir of Entamoeba histolytica?

Humans Signup and view all the answers

What is the primary mode of transmission of Plasmodium to humans?

Through the bite of an infected mosquito Signup and view all the answers

What is the incubation period of Plasmodium in the human liver?

9-16 days Signup and view all the answers

What is the result of infected red cells obstructing blood vessels in the brain?

Cerebral malaria Signup and view all the answers

What is the name of the disease caused by Toxoplasma infection?

Toxoplasmosis Signup and view all the answers

How does Plasmodium develop in the mosquito?

In the gut of the mosquito Signup and view all the answers

What is the primary mode of transmission of Toxoplasma to humans?

Through eating undercooked meat Signup and view all the answers

What is the result of Plasmodium infection in immunocompromised individuals?

Severe infection Signup and view all the answers

What is the result of congenital Toxoplasma infection?

Blindness in newborns Signup and view all the answers

What is the primary mode of transmission of tapeworms to humans?

Ingestion of undercooked meat from infected cows Signup and view all the answers

What is the typical duration between initial exposure and the onset of the intestinal phase?

6 to 8 weeks Signup and view all the answers

What is the primary habitat of adult tapeworms?

The small intestine Signup and view all the answers

What is the typical length of a nematode?

Less than 2.5 millimeters Signup and view all the answers

What is the name of the disease caused by tapeworm infection?

Taeniasis Signup and view all the answers

What percentage of the world population is infected with Ascaris lumbricoides?

1/3 Signup and view all the answers

What is the usual length of an adult tapeworm?

Up to 5 meters Signup and view all the answers

Where do the larvae of Ascaris lumbricoides penetrate after being ingested?

Small intestine wall Signup and view all the answers

Where do the larval forms of the tapeworm typically lodge?

In various organs, including skin, liver, muscles, and the central nervous system Signup and view all the answers

How many eggs can a female Ascaris lumbricoides produce per day?

200,000 Signup and view all the answers

What is the name of the intermediate host of the tapeworm?

Cattle Signup and view all the answers

What is the duration of the lung phase of Ascaris lumbricoides?

6-14 days Signup and view all the answers

What is a common symptom of high-level tapeworm infection?

All of the above Signup and view all the answers

What is the effect of having large numbers of adult worms in the intestine?

Both obstruction, pains and malnutrition Signup and view all the answers

What is the duration of the life cycle of Ascaris lumbricoides from egg to mature adult?

2 months Signup and view all the answers

What is the condition caused by Ascaris lumbricoides in the lung?

Ascaris pneumonitis Signup and view all the answers

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.