INTRODUCTION TO PARASITES A Presentation By Ms R.Venkatajothi, MSc., MPhil, PhD Senior Lecturer Department of Microbiology Faculty of Medicine AIMST UNIVERSITY

OBJECTIVES The objectives of this lecture are to  The objectives of this lecture are to introduce students to the basic concepts of parasitology. introduce students to the basic concepts of parasitology.  Introduce the various terms related to parasitology.

INTRODUCTION  Parasites are eukaryotic, uni or multicellular organisms and most of them are motile.  The study of parasites is called parasitology.  Parasites are classified into 2 sub-kingdoms:  Protozoa (unicellular) parasites are classified according to morphology and means of locomotion.

Continued……  Metazoa (multicellular) include the worms (Helminths) and arthropoda e.g. ticks, lice. Characteristics of parasites Undergo simple to complex life cycle. Undergo simple to complex life cycle. Often involve two hosts. Often involve two hosts. Alternates sexual and asexual reproduction. Alternates sexual and asexual reproduction. Some are motile by flagella, cilia. Some are motile by flagella, cilia. Performs all functions – reproduction, digestion, respiration & excretion.

Types of PARASITES  Protozoa are categorized into different groups by modes of transmission into the host. Eg: Amoebae, Intestinal, oral and Genital flagellates, Blood and tissue flagellates, Malarial parasites, Coccidia, Ciliate protozoa etc., Eg: Amoebae, Intestinal, oral and Genital flagellates, Blood and tissue flagellates, Malarial parasites, Coccidia, Ciliate protozoa etc.,  Parasitic worms are categorized into three groups: Cestodes (tapeworms), Nematodes (roundworms), and Trematodes (flukes).

PARASITES OF MAN  Parasites can cause disease in humans.  Some parasitic diseases are easily treated and some are not.  The burden of these diseases often rests on communities in the tropics and subtropics, but parasitic infections also affect people in developed countries.

Protozoa  Structure Trophozoite: active feeding form. Trophozoite: active feeding form. Cyst: dormant resistant form. Cyst Entamoeba histolytica Trophozoites Cyst

Metazoa  Structure - Egg, Larvae, Male and female worm…. EggHook worm Egg of Hook worm Adult worm Adult worm

HOST – PARASITE RELATIONSHIP Symbiosis: Living together primarily for food. Types of symbiosis based on whether or not the association is detrimental to one of the two partners. (a) Commensalism Association that is beneficial to one partner and not disadvantageous to the other. Entamoeba (Eg: Entamoeba Coli and man)

Continued…… (b) Parasitism The parasite derives benefit from the host and always causes injury to the host, however mild may be (Eg: Genus Plasmodium species causing malaria). The benefited partner in parasitism is the “Parasite”.

Continued…… Definition of Parasite:- obtain its nutrient and other needs from a host; the host is an organism which supports the parasite. Parasite is an organism which lives in or on the host and obtain its nutrient and other needs from a host; the host is an organism which supports the parasite.

Types of Parasites (a) Endoparasite:-  The parasites that live inside the body of their host, e.g. Entamoeba histolytica. Usually the endoparasites cause most of the human diseases.  The Endoparasites are of the following types: Obligate Parasite, Facultative parasite, Accidental parasite and Aberrant parasite.

Continued…… (b) Ectoparasite:- ticks, mites etc. The Parasite lives on the outer surface or in the superficial tissue of the host. Eg., Lice, ticks, mites etc.

Types of Host (a) Definitive host:- Harbors the adult stage or sexual reproduction of parasite occurs in this host. (Eg: Taenia solium, T.saginata of man) (b) Intermediate host:- Harbors the larval or asexual stage of the parasite. (Eg: malarial parasites of man)

Reproduction in Protozoa   Asexual reproduction:- Simple binary fission (Eg. Ameoba, Giardia, Leishmania, Trypanosoma etc.) Multiple fission (Eg. Genus Plasmodium).   Sexual reproduction:- Conjugation: (Eg. Balantidium coli), Endodyogeny: (Eg. Toxoplasma), Gametogeny & Sporogony: (Eg. Genus Plasmodium).

General terms used in parasitology Carrier:- The person who is infected with the parasite but without any clinical or sub clinical disease is called a carrier. Control:- Control of a disease refers to check the possibility of dissemination of the infection and epidemics, and reduce and maintain a low level of parasitic infection prevalent in the human population.

Continued…… Disease:- The clinical manifestation of infection which shows active presence and replication of parasites causing damage in the host. Epidemiology:- The study of distribution and determinants of disease frequency in man.

Continued…… Incubation period:- The time interval between initial contact with an infectious agent and appearance of first sign and symptom of a disease. Pathogen:- The parasite that causes damage to the host.

Continued…… Parasitological cure:- The termination of an existing parasitic infection with permanent cessation of excretion of the cysts and trophozoites in case of protozoal infections and eggs, larvae in case of helminthic infections. Pathogenicity:- The capability of a parasitic agent to cause disease in a susceptible host.

Continued…… Reservoir:- Any person, animal, arthropod, plant, soil and substance in which an infectious agent normally lives and multiplies, on which depends primarily for survival and where it reproduces itself in such a manner that it can be transmitted to a susceptible host.

PROTOZOA Entameba histolytica Giardia lamblia

PROTOZOA

Metazoa Ancylostoma duodenale (Hook worm) Egg Male & Female worm Male & Female worm

Metazoa Ascaris lumbricoides Egg Male & Female worm Male & Female worm

NAME OF THE PROTOZOA DISEASES Entamoeba hystolytica Amebiasis (amebic dysentery, amebic hepatitis) Giardia lamblia Giardiasis lambliasis Cryptosporidium parvum Cryptosporidiosis NAME OF THE HELMINTHS NAME OF THE HELMINTHSDISEASES Ascaris lumbricoides (roundworm) Ascariasis Ancylostoma duodenale (hookworms) Ancylostomiasis Trichuris trichiura (whipworm) Trichuriasis

PREVENTION OF A PARASITIC INFECTION An infection by intestinal parasites can be prevented by: An infection by intestinal parasites can be prevented by: Hand washing with soap before eating and after visiting toilet, touching soil or pets etc., Hand washing with soap before eating and after visiting toilet, touching soil or pets etc., Cooking kills all parasites in food (but smoking or freezing does not). Children should not walk / play by barefoot. Cooking kills all parasites in food (but smoking or freezing does not). Children should not walk / play by barefoot. Infection can be avoid by proper washing of raw vegetables and fruits and cook meat and fish well. Avoid suspicious restaurants with poor hygiene. Infection can be avoid by proper washing of raw vegetables and fruits and cook meat and fish well. Avoid suspicious restaurants with poor hygiene.

LEARNING OUTCOMES At the end of this lecture, students should be able to: At the end of this lecture, students should be able to: Restate the basic concepts of parasitology. Restate the basic concepts of parasitology. Define of the various terms related to basic parasitology. Define of the various terms related to basic parasitology.

LIST OF REFERENCE BOOKS Text book of Medical Parasitology ( Protozoology & Helminthology ) by Subhash Chandra Parija. Text book of Medical Parasitology ( Protozoology & Helminthology ) by Subhash Chandra Parija. Medical Microbiology by Murray. Medical Microbiology by Murray. Medical Microbiology by Jawetz, Melnick, & Adelberg's. Medical Microbiology by Jawetz, Melnick, & Adelberg's.