Parasitology

Introduction

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.

The relationship between two living organisms may be one of the following:- Mutualism Symbiosis Commensalisms Parasitism 1 2 3 4

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

Continue Symbiosis: Mutual benefit , and the two organisms can not live independently (physiological relationship). Benefit Benefit

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

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

Parasitism Parasite Host

Types of Parasites

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

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.

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.

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.

Occurs in one particular host. Continue Specific Parasite:- Occurs in one particular host. Pathogenic Parasite:- Causing injury to the host.

Coprozoic Parasite:- [copro= faeces] Continue Coprozoic Parasite:- [copro= faeces] Parasite passes the alimentary canal without infection or contaminant faeces after release.

Types of Hosts

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.

Definitive Host Secondary Host І ІІ ІІІ Accidental Host Main Host Continue Definitive Host Main Host Secondary Host Accidental Host І ІІ ІІІ

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.

In which its occurrence and development is very difficult. Continue Accidental Host:- In which its occurrence and development is very difficult.

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.

Factors Affecting Prevalence & Geographical Distribution of the Parasites

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.

[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.

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].

General Modes of Parasites Transmission

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].

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.

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)]

- 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)]

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.