Parasitology Parasitology

Parasitology- science that deals Parasitology- science that deals with the study of organism that with the study of organism that depends on another organism for depends on another organism for the purpose of procuring food and the purpose of procuring food and securing protectionsecuring protection

parasitesparasites hosthost

Types of hostTypes of host

Final or definitive host- harbors the Final or definitive host- harbors the adult stage of the parasite ex. Man, adult stage of the parasite ex. Man, dog, catdog, cat

Intermediate host- harbors the larval Intermediate host- harbors the larval stage of the parasitestage of the parasite

First intermediate host- harbors the early First intermediate host- harbors the early larval stage of the parasite ex. snaillarval stage of the parasite ex. snail

Second larval stage- harbors the infective Second larval stage- harbors the infective larval stage of the parasite ex. Fish, larval stage of the parasite ex. Fish, vegetablesvegetables

Reservoir host- host that ensures the Reservoir host- host that ensures the continuity of the life cycle of the continuity of the life cycle of the parasite and acts as an additional parasite and acts as an additional source of infection ex. Rodent, pigssource of infection ex. Rodent, pigs

Paratenic host- harbors the parasites Paratenic host- harbors the parasites in an arrested state of development. in an arrested state of development. However the parasite is capable of However the parasite is capable of continuing its life cycle in a suitable continuing its life cycle in a suitable host ex. Prawn, crabhost ex. Prawn, crab

Host- Parasite Host- Parasite RelationshipRelationship ParasitismParasitism MutualismMutualism CommensalismCommensalism SymbiosisSymbiosis

Factors affecting transmission of diseases The source of infectionThe source of infection An effective mode of transmission An effective mode of transmission

and portal of entryand portal of entry The presence of susceptible hostThe presence of susceptible host Successful entry of the infective Successful entry of the infective

stage of the parasitestage of the parasite

Sources of infectionSources of infection

Soil- ex. AscarisSoil- ex. Ascaris Snail- trematodesSnail- trematodes Arthropods-mosquitoArthropods-mosquito Animal/food borne- trichinella, Animal/food borne- trichinella,

taenia soliumtaenia solium Contact- trichomonasContact- trichomonas autoinfectionautoinfection

Mode of entryMode of entry

Mouth- ingestion, intimate oral Mouth- ingestion, intimate oral contactcontact

Skin- larval penetration, bite of Skin- larval penetration, bite of arthropodarthropod

OthersOthers– Genitals- trichomonas vaginalisGenitals- trichomonas vaginalis– Nose/intranasal- naegleria, enterobiusNose/intranasal- naegleria, enterobius– Transplacental- toxoplasma gondiiTransplacental- toxoplasma gondii

Life cycleLife cycle

Development of the parasite Development of the parasite which involves the survival and which involves the survival and development in the external development in the external environment and in one or more environment and in one or more hosthost

Diagnosis Diagnosis

Clinical diagnosis- diagnosis Clinical diagnosis- diagnosis based on the recognition of the based on the recognition of the characteristic signs and characteristic signs and symptoms of the infection.symptoms of the infection.

Laboratory diagnosis- diagnosis Laboratory diagnosis- diagnosis on the identification of the on the identification of the parasites in the different parasites in the different specimens.specimens.

Distribution of Distribution of DiseasesDiseases Endemic- when a disease in human Endemic- when a disease in human

population maintains a relatively steady, population maintains a relatively steady, moderate level.moderate level.

Epidemic- there is a sharp rise in the Epidemic- there is a sharp rise in the incidence or an out-break of disease.incidence or an out-break of disease.

Hyperendemic- if the prevalence of a Hyperendemic- if the prevalence of a disease in a community is high.disease in a community is high.

Sporadic- if the disease appears only Sporadic- if the disease appears only occasionally in one or few members of the occasionally in one or few members of the society.society.

Pandemic- when the disease covers Pandemic- when the disease covers extensive area of infection.extensive area of infection.

Prevention and ControlPrevention and Control

Reduction of the sources of infection in Reduction of the sources of infection in human beings via therapeutic measures.human beings via therapeutic measures.

Education in personal prophylaxis to Education in personal prophylaxis to prevent dissemination of infection and to prevent dissemination of infection and to reduce the opportunities of exposure.reduce the opportunities of exposure.

Sanitary control of water, food and Sanitary control of water, food and proper waster disposalproper waster disposal

Destruction or control of reservoir host Destruction or control of reservoir host and vectors.and vectors.

Erection of biological barriers to the Erection of biological barriers to the transmission of parasites.transmission of parasites.

Classification of Classification of ParasitesParasites According to habitatAccording to habitat

- endoparasite- endoparasite

- ectoparasite- ectoparasite According to the effect to the hostAccording to the effect to the host

- pathogenic- pathogenic

- non pathogenic- non pathogenic

According to the mode of livingAccording to the mode of living

- obligate- takes permanent - obligate- takes permanent residence and completely dependent on residence and completely dependent on the host for existence.the host for existence.

- facultative- capable of parasitic - facultative- capable of parasitic and free living under favorable condition.and free living under favorable condition.

- incidental- one that establishes - incidental- one that establishes itself in a host which it does not itself in a host which it does not ordinarily livesordinarily lives

- temporary- free living during - temporary- free living during part of existence and seeks only part of existence and seeks only its host intermittenly to obtain its host intermittenly to obtain nourishmentnourishment

- permanent- remains in or out of - permanent- remains in or out of the body of the host from early the body of the host from early life to maturity.life to maturity.