Assist Prof Dr. Syed Yousaf Kazmi

  Define parasitism  Classify parasites  Concept of life cycle of a parasite & host parasite relationship  Role of vectors in causing disease  List common parasitic infections OBJECTIVES

 PARASITE  A parasite is an organism that lives on or inside another organism to the detriment of the host organism  Traditionally parasite referred to organisms with life stages that needed more than one host PARASITISM  A form of symbiosis in which one organism (called parasite) benefits at the expense of another organism usually of different species(called host). INTRODUCTION

 Parasites that live on the surface of host are called Ectoparasites (e.g. lice, mite) Parasites that live inside the host are called Endoparasites (e.g. Giardia lamblia, Ascaris lumbricoides etc.) Parasites usually require more than one host for completion of life cycle e.g. Plasmodium falciparum INTRODUCTION

 INTRODUCTION TO BASIC PARASITOLOGY  Parasites are Eukaryotes  Two major groups  Protozoa (unicellular)  Metozoa/Helminth (Multicellular)- worms Trophozoite -trophē=nourishment, zōon=animal (active feeding stage of a protozoal parasite) Cyst/ oocyst -inactive and infective form Protozoa-motility via pseudopods, flagella, cilia etc.

 INTRODUCTION TO BASIC PARASITOLOGY  Helminths-worms  Definitive host-which harbor sexual phase of parasite  Intermediate host-which harbor asexual phase of parasite

  Two main groups 1. Parasitic protozoa (Unicellular) & 2.Parasitic helminths (Multicellular)  PROTOZOA a. Flagellates have one or more whiplike flagella e.g. Giardia lamblia, Trichomonas vaginalis b. Amebae use pseudopodia or protoplasmic flow to move e.g. Entamoeba histolytica, Naegleria fowleri c. Sporozoa undergo a complex life cycle, alternating sexual & asexual phases e.g. Plasmodium spp, Cryptosporidium spp d. Ciliates are complex protozoa bearing cilia e.g. Balantidium coli CLASSIFICATION

  HELMINTHS a.Nematoda (roundworms)  Elongated, round and un- segmented  Complete digestive system, highly developed separate-sexes  Eggs & larva- suited for external environment.  Most human infections- ingestion of egg or larva  Examples Ascaris lumbricoides, Ankylostoma duodenale, Enterobius vermiculoaris etc CLASSIFICATION

 b.Platyhelminthes  Flatworms are flattened, hermaphroditic, with a few exceptions  Two classes, Trematoda (flukes) & Cestoda (tapeworms). I. Trematoda (flukes) Fasciola hepatica, Clonorchis sinensis, Schistosoma spp II.Cestodes, or tapeworms Taenia solium, Echinococcus granulosus, CLASSIFICATION Fascioloa hepatica Taenia saginata

  Direct Life cycle  Only humans are host  Infective stage like ovum, cyst, larva passed out of body that infect healthy person  Example E histolytica, Giardia, Ascaris lumbricoides. LIFE CYCLE

 Life cycle of Taenia saginata  Indirect Life cycle  Multiple hosts or involvement of vector  Definitive host, Intermediate host  Example Taenia saginata spp, Schistosoma spp etc

  Parasites utilize nutrition from host resulting in damage  Loss of nutrition e.g. Iron def in hookworm infestation, Vit B 12 def in Diphyllobothrium latum  Morbidity-due to tissue injury e.g. E histolytica dysentery, severe itch due to Enterobius vermicularis  Mortality- fulminant diarrhea due to Cryptosporidium parvum inf & hyperinfection due to Strongyloides stercoralis in HIV HOST PARASITE RELATION Strongyloides stercoralis hyperinfection in HIV

  Vector, a Latin word meaning "carrier“  Imp in transmission of parasite  No direct damage by vector Anopheles  The Anopheles mosquito transmit Malaria, Filaria  Sandfly is vectors for Leishmaniasis  Domestic cats-vector of Toxoplasma gondii, Echinococcus granulosis ROLE OF VECTOR

  Amoebiasis: Entamoeba histolitica  Giardiasis: Giardia lamblia  Leishmaniasis: Leishmania donovani  Malaria: Plasmodium falciparum  Hook worm: Ancylostoma duodenale  Round worm: Ascaris lumbricoides  Echinococcosis: Echinococcus granulosa (tape worm)  Pin worm: Enterobious vermicularis  Scabies: Sarcoptes scabiei COMMON PARASITIC DISEASES Strongyloides stercoralis Entamoeba histolytica trophozoites