Introduction to medical parasitology. (1).pptx

Human parasite

1. MEDICAL PARASITOLOGY INTRODUCTION TO PARASITOLOGY DR TEMBO PAUL M.D UNZA ( MBCHB, BSC.HB )

2. Introduction to medical parasitology Parasitology ;the branch of biology concerned with the phenomenon of dependence of one living organism on another. It is the study of parasites , their hosts, and the relationship between them . Medical parasitology is the study of parasite which infest human beings as host . P arasite and Host Parasite : is an organism that lives in, on or upon its host, which is usually a larger organism, that provides physical protection and nourishment. They multiply or undergo development in the host.

3. Introduction to medical parasitology Types and Classification of Parasite According to the nature of the host interaction and the environmental factors, the parasite may be one of the following. Ectoparasite ; these parasites live on the outer surface or in the superficial tissues of the host (e.g. Lice. Mite , ticks etc ). The infection caused by these parasites is called infestation . Endoparasite ; the parasite which lives within the host ( e.g protozoan and helminthic parasites ). Invasion by the parasite is called infection .

4. Introduction to medical parasitology Endoparasites can be further classified as: Obligate parasite ; parasite that is completely dependant on the host and cannot survive without it example; Hookworms . Facultative parasite ; this parasite may either live as free living form or as a parasite when the opportunity arises. E.g N aegleria fowleri . Opportunistic parasite ; this parasite is capable of producing disease in an immune deficient host ( like AIDS and cancer patients ). E.g Toxoplasma gondii . Zoonotic parasite; parasite that primarily infects animals and is transmittable to humans. E.g fasciola species .

5. Endoparasite Classification continues…… Accidental parasite; parasites that infect an unusual host. E.g echnicoccus granulosa infects man accidentally . Wandering or Aberrant parasites ; parasite that infect host and migrate to the site where it cannot live or develop further. E.g Dog roundworm infecting humans .

6. Introduction to parasitology HOST Host; is an organism, which harbors the parasite and provide nutrition and shelter to the parasite. Host is relatively larger than parasite. Definitive Host : host which harbor the adult parasite or most highly developed form of parasite or where parasite multiply sexually. They can be human or non-human. E.g Mosquito acts as a definite host for plasmodiun spp. In malaria . Intermediate Host : the host in which the larval stages of the parasite live or in which asexual reproduction of the parasite takes place. e.g tsetse fly for trypanosomes , or man acts as an intermediate host for plasmodium spp. In malaria . Reservior Host : The host which harbour the parasite and acts has an important source of infection to other susceptable hosts. It is also called temporary host e.g dog is reservoir host for echynococcosis (disease kala azar )

7. Host classification continues……. Natural Host : the host which is naturally infected with a certain species of parasite e.g Pig is the natural host for Balantidium coli. Paratenic Host or Transport Host or C arrier Host; the host in which the parasite does mot undergo any development but remains alive till the parasite gain entry into the definitive host or intermediate host.

8. Introduction to parasitology Parasite and Host associations Symbiosis/mutualism; both the host and the parasite are dependent upon each other and none of the are harmed . Commensalism; only the parasite derives benefit from the association without causing any infection to the host. The parasite is capable of living independently . Parasitism; always harm the host due to their association. The parasite is dependent on the host for survival.

9. Introduction to parasitology Classification of medical parasitology Toxomonic classification of human parasites includes Ectoparasites Endoparasites Protozoan parasites (unicellular organisms) Helminthic parasites (multicellular organisms) M edically important parasites come under the kingdom called protista and animalia . Protista includes the microscopic single-celled eukaryotes known as protozoa . In contrast Helminths are macroscopic, multicellular worms possessing well differentiated tissues and complex organs belonging to the kindom animalia .

10. Introduction to parasitology Classification of medical parasitology Protozoa ( kingdom Protista-unicellular ) Amoebae e.g ( Entamoeba histolytica ) Flagillates e.g ( Giardia, T richomonas , Blood and Tissue flagellates, Leishmania ) Sporozoa e.g ( Plasmodium, Toxoplasmosis) Ciliates e.g ( Balantidum coli) Helminthes ( kingdom animalia -multicellular ) Nematodes e.g ( W uchereria bancrofti , A scaris sp ) Platyhelminths ( flatworms) Cestodes (tape worms) e.g Taenia solium , Taenia saginata . Trematodes (flukes ) e.g F asciola (liver fluke), Schistosomia (blood fluke )

11. Introduction to parasitology Life cycle of Parasites Direct life cycle T he life cycle of parasites that requires only single host to complete its development, is called d irect life cycle . Example; E ntamoeba histolytica requires only human host to complete its life cycle . Indirect l ife cycle The life cycle of parasites that requires two or more species of hosts to complete its developmet , is called indirect life cycle . Example; Malarial parasites( plasmodium spp ) requires both human host and mosquito to complete its life cycle .

12. Introduction to parasitology Transmission of Parasites It depends on the source or reservior of infection, and mode of transmission. Source of infection. Humans: Human is the source or reservior for majority of parasitic infection. The condition in which the infection is transmitted from one human to another human is called anthroponoses . Animals: animals act as the source of infection in many parasitic diseases. The condition where infection is transmitted from animals to humans is called zooonoses . Mode of transmission. Oral transmission: T his is through ingestion of contaminated food, water, vegetables, soiled fingers or fomites contaminated by faeces that contain the infective stage of parasite. This mode of transmission is referred to as f aecal-oral route . Example: cysts of Entamoeba hisolytica .

13. Introduction to parasitology Transmission of Parasites Skin transmission : this is another important route. The infective larvae of hookworm enter the skin of persons walking bare footed on contaminated soil . Vector transmission: It could be a biological or a mechanical means. Many parasitic diseases are transmitted by insect bite. Example : sandfly is a vector for leishmania . Direct transmission by person to person contact: entamoeba , Giardia and Trichomonas are transmitted by sexual contact among homosexuals. Vertical transimission : I t is the transmission from mother to fetus . Example: Toxoplasmosis.

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