Trematode

Introduction Taxonomic position Phylum platyhelminthes Class Trematoda Order Digenea

Species Reside in Trematodes that have medical importance Clonorchis sinensis hepatic bile duct Fasciolopsis buski Small intestine Paragonimus westermani Lung, subcutaneous, etc. Schistosoma japonicum S.mansoni, etc portal system

General features Leaf-like flattened bodies with no body cavity; with oral and ventral suckers to aid attachment to their hosts

General features The tegument is a syncytial layer equipped with spines and muscles Digestive system degenerated，with a mouth, enclosed by the oral sucker but no anus. mouth→pharynx →esophagus → two digestive tracts Hermaphrodite or monoecious except blood flukes (dimorphism) , possessing both male and female reproductive organs, the appearance and position of which are very important taxonomically

Reproductive system of trematode Female: ovary, oviduct, ootype, Mehlis’ gland, seminal receptacle, Laurer’s canal, vitellaria, vitelline duct, & uterus Male: testis, vas efferens, seminal vesicale, cirrus,&cirrus pouch

Life cycle is complicated – indirect life cycle General features Life cycle is complicated – indirect life cycle Usually need one or two intermediate host – bio-helmiths The first intermediate hosts are usually fresh water snails

General features Asexual phase: Eggs can only develop (hatch) in the fresh water Asexual phase: Eggsmiracidium in watersporocyst in snail redia cercaria release in water encysted metacercaria in second intermediate host – infective stage Sexual phase Preadult (Juvenile)migrated to favorable residing site  adult worm  lay eggs egg miracidium sporocyst redia cercaria metacercaria

Egg has operculum except blood fluke General features Encysted metacercaria is usually the infective stage (Schistosoma-- cercaria) Egg has operculum except blood fluke Features reflecting adaptation to parasitism Organs of attachment developed Retardation of digestive system Highly developed reproductive system

Clonorchis sinensis (liver fluke,肝吸虫)

Introduction found from the biliary passage of a Chinese in Calcutta, India in 1874 firstly. Clonorchis sinensis is known as the oriental or Chinese liver fluke because it is distributed throughout Japan, Korea, China and Vietnam It is estimated that there are more than 30,000,000 humans getting infection in these areas

It is a food-borne pathogen, causes clonorchiasis The parasite also infects a number of other animals, including dogs, cats, pigs, and rodents, and these animals serve as reservoirs of infection --- zoonosis

Morphology Adult: 1- 2.5 cm, flat, size and shape like the seed of sunflower With oral sucker and ventral sucker The two testes of the male productive organ are branched

Sucker & spine Younger worm

pharynx oral sucker vitellaria digestive tract ventral sucker uterus Seminal receptacle ovary Excretory bladder Testis ceca

Eggs Average 29×17µm, yellow brown The smallest helminth egg Light bulb shape which also looks like sesame or water melon seeds Operculum with distinctive shoulders Spine or knob on posterior end Contains miracidium when discharged

well-developed miracidium operculum shoulders spine/knob well-developed miracidium

cercaria metacercaria

Life cycle

Life cycle Need two intermediate hosts 1st intermediate host: fresh water snails, miracidium developed to cercaria in intestine 2nd intermediate host: fresh water fishes or shrimps, cercaria to metacercaria in muscles Infective stage: metacercaria Infective route: oral consumption of infective stage Definitive host: human being Reservoir host: dogs, cats -- zoonosis Lodging site: hepatic bile duct

1st intermediate host: fresh water snails Parafossarulus striatulus Alocinma longicornis Bithynia fuchsianus

2nd intermediate host: fresh water fishes and shrimps Minnows or carps

Pathogenesis Stage responsible for the pathogenesis: adult worm Mechanical irritation – suckers Toxic effects – excretions, secretions, metabolites Biological interference – nutrition deprivation

Pathogenesis Invasion of biliary epithelium inflammation  cell infiltration and proliferation  thickening of the duct wall  occlusion  extensive involvement  fibrosis of the liver  hepatocirrhosis

Adult worm in hepatic bile duct

rabbit infected with Clonorchis sinensis shows fibrosis of the bile duct

rabbit infected with Clonorchis sinensis shows hepatocirrhosis

hepatocirrhosis

Clinical features Asymptomatic to heavy bile duct diseases Hepatomegaly, jaundice, pancreatitis, bile duct stones, biliary cancer Maximum worm burden report >70,000 worms In child, symptoms are usually more serious, could also show malnutrition, nanoid, anemia and sometime causes death

Clonorchiasis patients Clinical features Enlargement of liver and spleen

Clonorchiasis patients Clinical features Clonorchiasis patients Hepatocirrhosis with ascites nanoid kid

Diagnosis History of eating raw fish or shrimps Etiological exams Kato-Katz method Sedimentation method is the choice for fecal or duodenal aspiration examination if egg burden is low Immunological diagnosis ELISA for specific antibodies or circulating antigens

Epidemiology and control Distributed in the Far East including China, Korea, Japan, Vietnam and far east part of Russia In china, it covers 25 provinces with the highest prevalence in Guangdong (5,000,000 cases), totally 10,000,000 reported cases over the country in year 2003 survey Dietary habit is the hard part for the disease control

Epidemiology and control Factors associated with endemic: Existence patients and reservoir hosts (cats & dogs) Presence of first & second intermediate hosts in the same water body Mode of fish breeding Dining habit and custom

Epidemiology and control Control measurements: Hygiene education – avoid eating raw or undercooked freshwater fishes; separate the raw and cooked food preparation area Protect fish pond from being contaminated by the feces Control of reservoir hosts – pets at home, no raw fresh-water fish for cats Cure patients and carriers – Praziquantel (drug of first choice), 25mg/kg，tid×3d