1 Medical Parasitology (MPG 2610) L1.pdf

Medical Parasitology (MPG 2610) Introduction to Parasitology Lecturer: Mwila Kabwe Learning Objectives Discuss the various types of parasites and hosts Explain the relationship between a parasite and the host and their effects Discuss in detail the classification...

Medical Parasitology (MPG 2610) Introduction to Parasitology Lecturer: Mwila Kabwe Learning Objectives Discuss the various types of parasites and hosts Explain the relationship between a parasite and the host and their effects Discuss in detail the classification of medically important parasites Explain the difference between the Cestodes, Nematodes, Trematodes and protozoa Introduction to Medical parasitology Medical parasitology is the science that deals with organisms living in the human body (the host) Also deals with the medical importance of this host-parasite relationship This definition could include viruses, bacteria and fungi as well as protozoa and helminths Introduction to Medical parasitology However, viruses, bacteria and fungi are studied in microbiology while protozoa and helminths in parasitology Parasites included in medical parasitology are protozoa, helminthes and some anthropods Relationship Between Parasite and Host Parasite: A living organism that take nourishment from the host Host: An organism which supports the parasite Relationship Between Parasite and Host Mutualism/Symbiosis: When both organisms are metabolically dependent upon each other and one cannot live without the other, however, non suffers any harm from the association e.g flagellated protozoa living in gut of termites Commensalism: When one organism benefit from another without causing injury to the host e.g. normal flora Parasitism: Where the host is harmed and the other lives at its expense e.g. Worms Types of Parasites Ectoparasite: A parasitic organism that lives on the outer surface of its host e.g lice, ticks, mites etc Endoparasites: Parasited that live inside the body e.g Entamoeba histolytica Obligate Parasite - This parasite is completely dependent on the host during a segment or all of its life cycle, e.g. Plasmodium spp. Types of Parasites Facultative parasite: an organism that exhibits both parasitic and non- parasitic modes of living and hence does not absolutely depend on the parasitic way of life, but is capable of adapting to it if placed on a host. E.g. Naegleria fowleri Accidental parasite: when a parasite attacks an unnatural host and survives. E.g. Hymenolepis diminuta (rat tapeworm). Erratic parasite - is one that wanders in to an organ in which it is not usually found. E.g. Entamoeba histolytica in the liver or lung of humans Types of Hosts Definitive host: a host that harbors a parasite in the adult stage or where the parasite undergoes a sexual method of reproduction. Intermediate host: harbors the larval stages of the parasite or an asexual cycle of development takes place. In some cases, larval development is completed in two different intermediate hosts, referred to as first and second intermediate hosts. Paratenic host: a host that serves as a temporary refuge and vehicle for reaching an obligatory host, usually the definitive host, i.e. it is not necessary for the completion of the parasites life cycle Types of Hosts Reservoir host: a host that makes the parasite available for the transmission to another host and is usually not affected by the infection. Natural host: a host that is naturally infected with certain species of parasite. Accidental host: a host that is under normal circumstances not infected with the parasite Effects of Parasites on the Host Direct: Mechanical injury Deleterious effect of toxic substances Deprivation of nutrients, fluids and metabolites Indirect: Immunological reaction Excessive proliferation of certain tissues due to invasion of some parasites  Classification of Medical Parasitology Medical Protozoology: study of microscopic single-celled eukaryotes in the kingdom Protista known as protozoa Medical Helminthology: study of macroscopic, multicellular worms possessing well-differentiated tissues and complex organs belonging to the kingdom Animalia Medical Entomology: The study of arthropods which cause or transmit disease to man Phylum Subphylum Class Order Family Species Genus General Characteristics of Protozoa Body is formed of cytoplasm and nucleus Cytoplasm is differentiated into ectoplasm and endoplasm Nucleus contains karyosome and peripheral chromatin Different types of protozoa include: Rhizopoda Flagellates Ciliates Coccidia Rhizopoda (Amoeba) Locomotion organs: Pseudopodia Habitat: Intestinal and free living General outline the life cycle and important stages: Trophozoite and cyst. E.g. Entamoeba histolytica Ciliates Locomotion organs: Cilia Habitat: Intestinal General outline of the life cycle and important stages: Trophozoite and cyst. E.g. Balantidium coli Mastigophora (Flagellates) Locomotion organs: Flagella Habitat: Intestinal, urogenital and blood General outline of the life cycle and important stages: Intestinal and urogenital flagellates: Trophozoite and cyst e.g. Trichomonas and Giardia Blood Flagellates Leishmania: Amastigotes (in human) and promastigotes (Vector) Trypanosoma: Trypomastigotes (human) and Epimastigotes (Vector) Coccidia (Sporozoa) Locomotion organs: They are sporulated/none They are members of Apicomplexa Habitat: Intestinal, tissue and blood Coccidia (Sporozoa) General outline of the life cycle: Gametogony (sexual reproduction) Important stages in the life cycle: Sporozoite, Schizont, merozoite, gametocytes, oocyst. E.g. Plasmodium spp. Helminthes Helminthic parasites are multicellular, bilaterally symmetrical animals having three germ layers They are divided into Cestodes, Trematodes and Nematodes Differentiating features of Helminthes- Trematodes Hemaphrodite except blood flukes (Unisexual) Leaf like, flattened and bilaterally symmetrical There do not have a body cavity  Differentiating features of Helminthes- Trematodes Almost all have 2 suckers, oral (at the anterior end, around the mouth) and ventral (on the ventral surface) Many different habitats: intestinal, hepatic, blood and pulmonary flukes Adult Egg Miricidium Sporocyst Redia metacercaria Cercaria  Differentiating features of Helminthes- Cestodes (Tapeworms) Hemaphrodite, Ribbon-like flattened and bilaterally symmetrical There is neither body cavity nor digestive tract All intestinal parasites Differentiating features of Helminthes- Cestodes (Tapeworms) Composed of three body parts; Head (Scolex) provided by organs of attachment Neck is composed of actively dividing cells, responsible for new segments Body composed of several segments (Immature, mature and gravid segments) Suckers (4) with or without hooks arranged in circles on the apex of scolex called “rostellum” Bothria (2) that take the form of grooves Differentiating features of Helminthes- Cestodes (Tapeworms) Adult Egg Cysticercus (larval stage) Adult All cestodes require one intermediate host (usually vertebrate) Nematodes (Cylindrical worms) Bilateral Symmetrical Has body cavity Separate sexes Elongate and cylindrical Nematodes (Cylindrical worms) Organs of fixation are present in the mouth and buccal cavity as lancets and teeth Intestinal and tissue nematodes Adult Egg larval Adult Differentiating features of Helminthes CESTODE TREMATODE NEMATODE Shape Tape like, Leaf life, Elongated, segmented Unsegmented Cylindrical Sexes Not separate Not Separate Separate (diecious) (Monoecious) (Monoecious) Except blood flukes which are dioecious “Head” End Suckers with hooks Suckers: no hooks No suckers, and hooks Alimentary Canal Absent Present but Present and incomplete complete Body Cavity Absent Absent Present Arthopods Form the largest group of species in the animal kingdom Characterised by having a bilaterally symmetrical and segmented body with jointed appendages They have a hard exoskeleton Arthopods They have an open circulatory system with or without a dorsally situated heart Arthropods affect the health of humans by being either direct agents for disease or agents of disease transmission  Classification of Arthropods Kingdom Animalia Phylum Arthropoda Class Crustacia Arachnida Insecta Chilopoda Pentastomida e.g. Scorpion e.g. Ticks e.g. Mosquito e.g. Centipedes e.g. tongue worms Summary????