Helminths

Introduction about helminths with classification

1. helminths DR. SUMESH KUMAR DASH PG RESIDENT, DEPARTMENT OF MICROBIOLOGY, IMS & SUM HOSPITAL.

2. GENERAL CHARATRISTICS Helminths are elongated flat or round worm like parasites measuring few milometers to meters. They are eukaryotic multicellular and bilaterally symmetrical They belongs to two phyla Phylum Platyhelminths (flat worms)— it includes three classes: Cestoidea (tapeworms) Trematodea (flukes or digeneans) Monogenea (ectoparasite of fishes, don’t infect man) Phylum: Nemathelminths.

3. PROPERTIES CESTODE TREMATODE NEMATODE SHAPE Tape-like and segmented Leaf-like and unsegmented Elongated, cylindrical and unsegmented HEAD END Suckers present Some have attached hooklets Sucker, present No hooklets. No sucker No hooklets. Some have well developed buccal capsule ALIMENTARY CANAL Absent Incomplete Complete from mouth to anus BODY CAVITY Absent Absent Present SEX Monoecious Monoecious Diecious LIFE CYCLE Required 2 Host Required 2 Host Required 1 Host

4. MORPHOLOGY In general, helminths exist in three morphological forms Adult form (or the worm) Larval form Eggs Oviparous: Most of the helminths (cestodes, trematodes and many nematodes) are oviparous, i.e. after fertilization, the adult worm lay eggs Viviparous: Only few nematodes directly discharge the larval forms after fertilization (e.g. Filarial worm, Dracunculus and Trichinella) Ovoviviparous : They lay egg containing larva that immediately hatches out (e.g. Strongyloides)

5. CLASIFICATION CESTODE TREMATODE NEMATODE Intestinal Taenia solium (Pork tapeworm) Taenia saginata (Beef tapeworm) Hymenolepis nana (Dwarf tapeworm) Hymenolepis dimunita (Rat tapeworm) Diphyllobothrium latum (Fish tapeworm) Somatic/tissue Taenia multiceps Echinococcus granulosus (Dog tapeworm) Spirometra spp. Blood Schistosoma (Blood fluke) Hepatic Fasciola hepatica ( Common liver flukes / Sheep liver fluke) Clonorchis sinensis (Chinese or Oriental liver fluke) Opisthorchis felineus (Cat liver fluke) Intestinal Fasciolopsis buski (Giant intestinal fluke) Heterophyes spp. Metagonimus spp. Watsonius spp. Gastrodiscoides spp. Lung Paragonimus westermani (Oriental lung fluke) Large intestine Trichuris trichiura (Whipworm) Enterobius vermicularis (Pinworm) Small intestine Ascaris lumbricoides (Round worm) Ancylostoma duodenale (Hook worm) Necator americanus Tissue Filarial worm Wuchereria bancrofti Brugia malayi Loa loa Onchocerca volvulus Mansonella spp. Trichinella spiralis Dracunculus medinensis

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