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What is Parasitology?
The scientific discipline concerned with the study of the biology of parasites and parasitic diseases.
Define parasite.
A living organism that takes its nourishment and other needs from a host.
Define host.
An organism which supports the parasite.
What is zoonosis?
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Which type of partnership involves both organisms being dependent on each other?
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What are ectoparasites?
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What is a definitive host?
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What does a facultative parasite do?
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A reservoir host is affected by the infection from the parasite.
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What is an accidental parasite?
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Contaminated ______ and water can be a source of infection.
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What is the commonest portal of entry of parasites?
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Through which portal of entry do larvae of filariform nematodes commonly penetrate?
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Study Notes
Introduction to Parasitology
- The study of parasites and their relationship with hosts, including biology, distribution, and host response.
- Parasites depend on hosts for nourishment and survival.
- Hosts provide resources to parasites, but may suffer harm.
- Zoonosis refers to infectious diseases that transmit from animals to humans.
Types of Partnerships
- Symbiosis: Mutual dependence between organisms without harm.
- Commensalism: Parasite benefits without harming the host.
- Parasitism: Parasite benefits at the host's expense.
Types of Parasites
- Ectoparasites: Live on the host's outer surface (e.g., lice, ticks).
- Endoparasites: Live inside the host's body (e.g., Entamoeba histolytica).
- Obligate Parasite: Completely dependent on a host for survival (e.g., Plasmodium spp.).
- Facultative parasite: Can survive independently but adapts to parasitic life (e.g., Naegleria fowleri).
- Accidental parasite: Infects an unnatural host (e.g., Hymenolepis diminuta in humans).
- Erratic parasite: Wandering outside its usual habitat within the host (e.g., Entamoeba histolytica in the liver or lung).
Types of Hosts
- Definitive host: Harbors the parasite in its adult stage or where sexual reproduction occurs.
- Intermediate host: Harbors larval stages or asexual reproduction.
- Paratenic host: Serves as a temporary refuge for the parasite without essential development (e.g., a fish in a tapeworm life cycle).
- Reservoir host: Carries the parasite and transmits it to other hosts, often without displaying symptoms.
- Natural host: Naturally infected with a specific parasite species.
- Accidental host: Unusually infected with a parasite outside its normal range.
Sources of Infection
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Contaminated soil and water:
- Diphyllobothrium latum and Clonorchis sinensis (freshwater fish)
- Paragonimus wertermani (crabs and crayfishes).
- Fasciola hepatica (watercress)
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Raw or undercooked meat:
- Trichinella spiralis, T. solium (pork)
- T. saginata, Toxoplasma gondii (beef)
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Blood-sucking insects:
- Vectors for various parasites (e.g., mosquitoes, ticks)
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Houseflies:
- Mechanical carriers of E. histolytica.
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Animals:
- Dogs: Echinococcus granulosus and Toxocara canis.
- Cats: T. gondii.
- Humans: E. histolytica, Enterobius vermicularis, and H. nana.
Portals of Entry
- Mouth: Commonest route (e.g., contaminated food, water, or fingers).
- Skin: Penetration by larval stages (e.g., hookworms), cercarial larvae (e.g., Schistosomiasis).
- Sexual contact: Trichomonas vaginalis.
- Congenital: Transplacental transmission (e.g., T. gondii, Plasmodium spp.).
- Inhalation: Respiratory infections.
- Iatrogenic infection: Blood transfusion (e.g., Malaria).
Parasite Transmission
- Direct: Person-to-person contact.
- Indirect: Through contaminated objects or vectors (e.g., insects, animals, water, soil).
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Description
This quiz explores the fascinating field of parasitology, focusing on the relationships between parasites and their hosts. It covers types of partnerships, various parasites, and their characteristics, including ectoparasites and endoparasites. Understand the impact of these organisms on their hosts and the significance of zoonosis in infectious diseases.
