INTRODUCTION TO TREMATODES Dr.Jagadeesh (P.G)27-7-15

1. INTRODUCTION TO TREMATODESDr.Jagadeesh (P.G)27-7-15

2. Helminths are elongated, flat or round worm, parasites. Few mm to meters in size. • Eukaryotic, multicellular and bilaterally symmetrical. • Belong to two phyla Platyhelminths----class-cestoidea,tramatodea and monogenea Nemathelminthis

3. Class-Cestoidea---Order---Pseudophyllidea----Family---Diphyllobothriidae—Class-Cestoidea---Order---Pseudophyllidea----Family---Diphyllobothriidae— Genus---Diphyllobothrium and Spirometra Order– Cyclophyllidiae--- Family—Taeniidae— Genus---Taenia and Echinococcus Family--- Hymenolepidiidae--- Genus---Hymenolepsis Family---- Dipylidiidae— Genus---Diphylidium

5. Trematodes or flukes belong to— Phylum-------Platyhelminths Class----------Digenea

6. Trematodes or flukes are unsegmented ,flat and leaf like . • They have suckers but no hooklets . • They have incomplete alimentary canal . • No body cavity and are monoecious . • Require three hosts . • Larval form includes-Cercaria,Metacercaria,Redia , Meracidium and Sporocyst .

7. Classification of Trematodes

8. Classification based on habitat Blood Trematodes— Schistosoma hematobium-vesical venous plexus Schistosoma mansoni ,S.japonicum-rectal and portal venous plexus

9. contd • Hepatic Trematodes Fasciola hepatica and Fasciola gigantica-both resides in liver Clonorchis species—in bile duct Opisthorchis species—in bile duct

10. contd • Intestinal Trematodes Small intestine— Fasciolopsisbuski,Heterophyses species Metagonimus species ,Watsonius species • Large intestine –Gastrodiscoides species • Lung Trematode-- Paragonium Westermani

11. General characteristics • Trematodes exist in three morphological forms—adult form, egg and larva . • Adult worm unsgmented and flattened dorsoventrally ,some may have thick fleshy bodies( Schistosomes ). • Size 1 mm to 60mm

14. They have two suckers to attach to host . • Oral sucker is anterior and surrounds mouth. • Ventral sucker or acetabulum on ventral surface .

15. Digestive system—It is incomplete , consist of anterior mouth , muscular pumping pharynx continue as esophagus. • Esophagus bifurcates infront of ventral sucker into a pair of blind intestinal pouchs called caeca or crura • It may be simple as in C .sinensis or branched as in F.hepatica or may reunite to form a single caecum. • The anus is absent.

16. Most trematodes are hermoprodite except Schistosomes which are diecious . • Male sexual organ consists of number of testes present near cecal end , vas efference arise from each testes and join to form a common vas diference . • It runs via seminal vesicle and opens at genital pore situated near ventral sucker .

17. Female reproductive organs consists of—an ovary present near the ventral sucker. • Vitelline glands surrounding ovary,ovi duct ,ootype and a uterus contaning eggs that opens behind the ventral sucker

18. The excretory system is bilaterally symmetrical. • Contains flamme cells and collecting tubules which lead to a median bladder opening at the posterior end of body,usually on the dorsal aspect .

20. The nervous system consists of paired ganglia at the anterior end . From this nerves extend anteriorly and posteriorly

21. They are oviparous . • Eggs are operculated except that of schistosomes . • Larva of trematodes have many forms—miracidium ,sporocyst , redia,cercaria and metacercaria .

22. Trematode eggs

23. Life cycle • They complete their life cycle in three different hosts—one definitive and two intermediate . • First intermediate host is fresh water snail or mollusc and second is either an aquatic plant or fish or crab . • Schistisomes dont need a second host . • Mode of transmission—man get infected by eating aquatic plants ,fishes harboring infective forms (metacercaria ) or by penetration of free living cercariae

24. Development in definitive host • Young trematodes migrate to their habitat ,grow into adult worm , sexually mature and begins laying eggs. • Eggs in urine, feces or sputum gain access to water . • Depending on embryonation ,eggs show three different types of development • Eggs if embryonated hatch to release miracidia and infect intermediate host i.e snail (Schistosomes ) . • Non embryonated eggs first mature in water then hatch to release miracidia (Paragonium ,Fasciola) . • Eggs embryonated but hatch only on ingestion by suitable snail host (Clonarchis .Ophisthorchis )

25. Development in first intermediate host • Miracidium is the free swimming ciliated larva , penetrate suitable intermediate host. • Miracidium contains apical gland which release proteolytic enzyme help in penetration. • In liver or lymph space of intermediate host , miracidium tranforms into sporocyst . • Asexual multiplication doesnt occur at this stage except in schistosomes .

26. Contd • Sporocysts develop to become radiae ,which multiply to produce second generation rediae or transform into cercariae . • A single miracidium can give rise to a large number of cercariae . • No radiae stage in Schistosomes • Based on morphology of tail cercariae can be divided into four types . • In schistosomes , cercariae are infective to man , Where as in other trematodes metacercariae are infective

27. Types of cercarial larvae of Trematodes • Furcocercus cercaria –elongated body with forked tail (Schistosomes ) • Microcercus cercaria—oval body with short stumpy tail (Paragonimus ) • Lophocercus cercaria—Crecaria armed with spines, large fluted tail ,conspiuious eye spot (Clonarchis ) • Pleurolophocercus cercaria-spines ,pigmented eye spot and long keeled tail (Opisthorchis )

29. Types of cercaria • Furocercus cercaria—elongated body with forked tail—Schistosomes. • Microcercus cercaria---oval body with short stumpy tail—Paragonimus • Lophocercus cercaria---Cercaria armed with spines and has large fluted tail and conspicious eye—Clonarchis.Metagonium • Pleurolophocercus Cercaria—armed with spines ,pigmented eye spots with long keeled tail

30. Development in second intermediate host • After ingestion by fish or crab ,the cercarial larvae develop into metacercariae which are the infective form to definitive host

33. Answer the questions • Classify trematodes based on their habitat ? • Write short note on morphology of flukes ? • Write differences between Cestodes , Trematodes and Nematodes ? • Name the larval forms of trematodes ? • Name the types of cercarial larvae of Trematodes