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Parasitology
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Introduction
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Parasitology:- It is the science that deals with organisms that live on or within other organisms (Hosts). Mainly in this course branch we study the parasites which live on the expense of man.
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The relationship between two living organisms may be one of the following:-
Mutualism Symbiosis Commensalisms Parasitism 1 2 3 4
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Mutual benefits is derived from the association of these two organisms
Continue Mutualism:- Mutual benefits is derived from the association of these two organisms Benefit Benefit
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Continue Symbiosis: Mutual benefit , and the two organisms can not live independently (physiological relationship). Benefit Benefit
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Continue Commensalisms:- One partner benefits (commensal) while the other (host) is unaffected It may be called a non-pathogenic parasite. Benefit No harm ,No benefit
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Continue Parasitism:- One organism (parasite) lives at the expense of the other (host) which usually suffer from the association. It is called a pathogenic parasite. Benefit Harm
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Parasitism Parasite Host
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Types of Parasites
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Live outside the body of the host (infestation). e.g. Lice
Continue Ectoparasite:- Live outside the body of the host (infestation). e.g. Lice Endoparasite:- Live inside the host (infection). e.g. most of human parasite
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Facultative Parasite:-
Continue Facultative Parasite:- Capable of leading both a free-living and a parasitic existence (live parasitically or none parasitically). Obligate Parasite:- Completely dependent upon its host and can not lead a free life.
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Live parasitically during the whole life cycle.
Continue Temporary Parasite:- Parasitic only during part of its life cycle. Permanent Parasite:- Live parasitically during the whole life cycle.
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Incidental Parasite:-
Continue Incidental Parasite:- Can establish itself in a host in which it does not ordinary live (occur in abnormal host). Pseudoparasite:- A certificate mistaken as a parasite.
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Occurs in one particular host.
Continue Specific Parasite:- Occurs in one particular host. Pathogenic Parasite:- Causing injury to the host.
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Coprozoic Parasite:- [copro= faeces]
Continue Coprozoic Parasite:- [copro= faeces] Parasite passes the alimentary canal without infection or contaminant faeces after release.
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Types of Hosts
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Harbours the adult or mature parasite.
Continue Definitive Host (final or terminal):- Harbours the adult or mature parasite. In which parasite can reproduce sexually if it applicable.
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Definitive Host Secondary Host І ІІ ІІІ Accidental Host Main Host
Continue Definitive Host Main Host Secondary Host Accidental Host І ІІ ІІІ
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In which the parasite occur more frequently and reach maturity.
Continue Main Host:- In which the parasite occur more frequently and reach maturity. Secondary Host:- In which the parasite occur less frequently and growth is retarded.
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In which its occurrence and development is very difficult.
Continue Accidental Host:- In which its occurrence and development is very difficult.
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Continue Intermediate Host:- Harbours the immature stage of the parasite (larval stage) that reproduce asexually into infective stage. Reservoir Host:- Animal that harbours the same species of parasites as man and constitute a source of infection to him.
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Factors Affecting Prevalence & Geographical Distribution of the Parasites
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Availability of suitable hosts and their habits.
Continue Availability of suitable hosts and their habits. Immune status of the hosts. Easy entry & exit of the parasite to and from the host. Regional habits. Socio-economical status.
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[knowledge about parasites reduce the infections rates]
Continue Education [knowledge about parasites reduce the infections rates] Environmental sanitation [water, food, waste disposal,…..] Suitability of the environmental and climatic conditions.
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Control of intermediate hosts, treatment of infected cases….ect.
Continue Control of intermediate hosts, treatment of infected cases….ect. Nature of life cycle [e.g. parasites with simple life cycles have more distribution than with complicated cycles].
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General Modes of Parasites Transmission
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Congenital (through placenta) e.g. malaria
Continue Congenital (through placenta) e.g. malaria Direct Contact. [e.g. arthropods, Leshmania, Tichomonas & Entamoeba gingivalis ]. Indirect contact (in contaminated objects). [e.g. amoebic cyst, helminthes egg as of H. nana , Taenia , Entrobius].
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In flesh: [e.g. T. saginata & T. solium].
Continue In food as most parasites are intestinal and their infective stage reach food either: In flesh: [e.g. T. saginata & T. solium]. In contaminated water [e.g. vegetable with protozoa cyst & helminthes egg]. Contamination by insects [e.g. mechanically by housefly]. Contamination by food handler.
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Contaminated soil [e.g. Ancylostoma].
Continue In water: drinking contaminated water with protozoa cyst or helminthes egg or using water containing the intermediate host, infective stage [e.g. Schistosomiasis]. Contaminated soil [e.g. Ancylostoma]. Animals [e.g. dog worm (dog), Toxoplasmosis (cat)]
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- Transmission occurs either:-
Continue Arthropods: - Transmission occurs either:- Mechanically [e.g. faecal cyst & eggs to food by house fly]. Biologically [e.g. malaria & filariasis ( by mosquitoes), sleeping sickness (by Tsetse fly) & Leishmaniasis (by sand fly)]
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Dose is calculated according to the patient weight.
Continue Praziquantel is very safe, taken as a single or divided dose according to the worm type. Dose is calculated according to the patient weight. Praziquantel is swallowed, not chewed; as it is very bitter in taste.
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