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Questions and Answers
What is the main characteristic of an obligate parasite?
Which type of host is the organism in which the adult or final stage of the parasite develops?
What is the main difference between a facultative parasite and an obligate parasite?
Which host is the organism that harbors the larval (asexual) stage of the parasite?
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What is the main role of a vector in the transmission of parasites?
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Which type of host is the animal species on which the parasite depends for its survival in nature and acts as a source of infection for other hosts?
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What term is used for parasites that require a specific vector for their life cycle?
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Which type of vector is a house fly transmitting E.histolytica considered as?
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What is the term for a population of parasites that can interbreed and have the same genetic characters?
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Which term is used for an object that resembles a parasite but is not a parasite itself?
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In medical parasitology, which group includes protozoa, helminths, molluscs, and arthropods?
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What is the term for a disease that is transmitted from animals to humans?
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What is the term used to describe parasites that can live independently or as a parasite?
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Which term refers to parasites that live on the external surface of the host?
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How would you classify a host that is susceptible to a particular parasite but does not show clinical signs of disease?
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Which term is used to describe the development of damage caused by a pathogen in the host?
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What is the term used to describe the rate or frequency with which a disease occurs in a population?
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Which term is used to describe a disease that is constantly present in a population at a high prevalence?
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Study Notes
Scientific Names and Parasites
- A scientific name consists of a generic name with an initial capital letter and a specific name with an initial small letter.
- Parasites that injure the host are called pathogens, and the development of the damage is called pathogenesis.
Factors Affecting Pathogenesis
- The degree of injury depends on several factors:
- Potential virulence of the agent (intrinsic pathogenecity)
- Amount of inoculum and rapidity of multiplication
- Site of inoculation
- Exposure (single or repeated)
- Resistance or tolerance of the host to a particular strain of agent
- General resistance of the host
- Type of damage caused by the agent (mechanical, lytic, toxic, or allergic)
Epidemiology
- Incidence is the rate or frequency of new infections in a designated area.
- Endemic diseases are maintained at a stable rate of prevalence within a population.
- Hyper endemic diseases have a high prevalence.
- Sporadic diseases appear irregularly in scattered individuals.
- Epidemic diseases have a high prevalence in unusual transmission.
- These terms are specific to humans, while similar terms for animals are enzootic, hyper enzootic, epizootic, and sporadic.
Biological and Mechanical Vectors
- A biological vector is essential for the parasite's life cycle, e.g., Anopheles female transmitting Plasmodium.
- A mechanical vector is not essential for the parasite's life cycle, e.g., house fly transmitting E. histolytica.
Zoonosis and Classification
- Zoonosis is a disease transmitted from animals to humans, either incidentally or commonly.
- Classification of animal parasites and vectors includes:
- Coprozoic or spurious parasites (eggs or parasites that are not in their normal habitat)
- Wandering or aberrant parasites (parasites that reach a place where they cannot live)
- Pseudoparasites (objects that resemble parasites or eggs but are not parasites)
Major Groups in Medical Parasitology
- Four groups are of major importance in medical parasitology:
- Protozoa
- Helminths
- Molluscs
- Arthropods
Zoological Nomenclature
- Phylum, subphylum, and other larger divisions are used to classify organisms.
- Classes, orders, families, genus, and species are used to classify organisms in lesser divisions.
- All names must be of Greek or Latin origin.
Genus and Species
- A genus is a group of closely related species.
- A species is a population with the same genetic characters, capable of continued reproduction, and incapable of interbreeding with other species.
Types of Parasites
- Obligate parasites are entirely dependent on their hosts and cannot live outside the host.
- Facultative parasites are capable of living either free or in or on a host.
- Parasites can be classified by the duration of their association with their hosts:
- Temporary parasites visit a host for a short period.
- Permanent parasites lead a parasitic life all through their life.
Hosts
- The human or organism that harbors the parasite is called the host.
- Definitive host: the organism in which the adult or final stage of the parasite develops or where sexual reproduction occurs.
- Intermediate host: the organism that harbors the larval stage of the parasite.
- Paratenic host: a host in which the parasite is transported and neither gains nor loses infectivity for its definitive host.
- Reservoir host: an animal species on which the parasite depends for its survival in nature and acts as a source of infection for other hosts.
- Vector: a transmitter of parasites from host to host, or an agent of transmission.
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Description
Test your knowledge on parasite transmission and vector classification. Learn about biological vectors like Anopheles females and mechanical vectors like house flies. Explore the concept of zoonosis and how diseases can be transmitted from animals to humans.
