Definition & Conception of Parasitology

A) Definition of parasitology: 
1) Parasitology -
The study of parasites, their hosts and the relationship between them
2) Clinical parasitology -
The study of parasites and the parasitic diseases that may affects the hosts

The relevance of studies parasites and parasitic disease

Parasites	Morphology Life Cycle
	Pathogenesis
Parasitic Diseases
	Transmission Diagnosis Treatment Prevention

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B) Conceptions related to clinical parasitology:

1) Symbiosis
2) Parasites and type of parasites
3) Host and common type of hosts
4) Life cycle and common type of life cycles

Symbiosis
The relationship between two living things (animals). Two living things live together and involve protection or other advantages to one or both partners:
1. Commensalism
2. Mutualism
3. Parasitism

Commensalism	Both partners are able to lead independent lives, but one may gain advantage from the association when they are together and least not damage to the other
Mutualism	An association which is beneficial to both living things
Parasitism	An association which beneficial to one partner and harmful to the other partner. The former that is beneficial to is called parasite, the latter that is harmful to is called host

Parasites and type of parasites
Parasites, is an animals that is dependent on another animal (host) for it survivals. Types of parasites:
1. Protozoa
2. Helminthes
3. Arthropods

Protozoa
Helminthes	- Nematodes	→	Endoparasites	A parasites which lives in the body of the host
	- Trematodes
	- Cestodes
Arthropods		→	Ectoparasites	A parasite which lives on the body of the host

Host and common type of hosts
Host, is an organisms that harbors the parasites usually larger than the parasite. Type of hosts:
1. Intermediate host
2. Final host
3. Reservoir host

Intermediate host	The host harboring the larvae or asexual stage of parasite
Final host	The host harboring adult or sexual stage of parasite
Reservoir host	Animals harboring the same species of parasites as man. Potential sources of human infection

Life cycle and common type of life cycles
life cycle is the whole process of parasite growing and developing. Type of life cycles:
1. Direct life cycle
2. Indirect life cycle

Direct life cycle	Life cycle with only one host (no intermediate host)
Indirect life cycle	Life cycle with more than one host (intermediate host and final host)

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C) Relationship (effect) between parasites and host:

1) Effect of parasites on the host

2) Effect of host on the parasites

↗produce mechanical injuries to the host ↘

Parasite →             harbor in the            → Host

↖Produce immune response to the parasite↙

Effect of parasites on the host

1. Depriving the host of essential substance

(e.g. Hookworm → suck blood → anemia)

2. Mechanical effect of parasites on the host

(e.g. Ascaris → perforated/obstruction)

3. Toxic and allergy effect

(e.g. E. Hystolitica → proteolytic enzyme → necrosis)

(e.g. parasite antigen → immune system → anaphylaxis)

Effect of host on the parasites
The host can produce certain degree resistance to parasites in human body or re-infection. the resistance (immunity) is not very strong. In general, it don't wipe out parasites completely, but may limit the number of parasites and establish balance with parasites. Type of immunities:
1. Innate immunity
2. Acquired immunity

Innate immunity	1. Barrier: prevent parasites to invade in certain degree from skin / mucous membrane / placenta 2. Acid in skin or stomach: can cause damage of the parasites 3. Phagocytosis of phagocyte: non-specific / effective against a wide range of parasitic infection / controlled by genetic factors → BUT NOT VERY STRONG
Acquired immunity	Mechanism: Cellular and humoral immunity - Sterilizing immunity: wipe out the parasites completely, meanwhile get a long-term specific resistance to re-infection → RARE - Non-sterilizing immunity: wipe out most of the parasites, but not completely → COMMON → NO PARASITE, NO IMMUNITY

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Next → Basic Transmission & Prevention of Parasitic Disease