LU 3.2b Intestinal & Liver Parasites II

What are the general characteristics of helminths?

• it is macroscopic in size for adult, often visible to naked eye

• multicellular, bilaterally symmetrical, elongated round organisms

What are the two groups of helminths of medical importance to humans?

• Phylum Nematoda (Roundworms)

• Phylum Platyhelminthes (Cestodes and Trematodes)

What are the classification of trematodes?

• Blood trematode

• Liver trematode

• Intestinal trematode

• Lung trematode

What are the general differences between nematodes, cestodes and trematodes?

What are the general characteristics of trematode (Flukes) ?

• Unsegmented leaf-shaped worms, no body cavity

• simple digestive system

• excretory system is bilaterally symmetrical

• reproductive system is highly developed system

Explain the life cycle of trematodes

What are the mechanism of transmission of trematode?

1. Cercariae : free swimming larvae

2. Metacercariae : water plants, fish

Explain the general characteristics of Intestinal Trematode : Fasciolopsis buski

• is is the largest trematode infecting human

• diseases : fasiolopsiasis

• definitve host : human & pig

• transmission : consumption of under-cooked water plants containing metacercariae

Explain the adult and eggs stage of fasciolopsis buski

• Adult : i) fleshly dark red and elongated oval fluke ii) live in small intestine iii) life span about 1 year

• Eggs : broadly ellipsoidal, operculated, light yellowish brown

Explain the mechanism of transmission of fasciolopsis buski

• human become infected by ingesting waterplants containing metacercariae

• after ingestion, metacercariae excyst in duodenum and attached to the intestinal wall

What are the clinical manisfestation/effects of fasciolopsis buski

• Clinical manisfestations : heavy infections can cause abdominal pain, nausea, vomitting and fever

Explain the general characteristics of liver trematode : Fasciola hepatica

• it is large leaf-like fluke

• brown to pale in colour

• disease : fascioliasis

• definitive host : humans, sheep, goats

• transmission : consumption of under-cooked watercress containing metacercariae

Explain the general characteristics of adult and eggs of fasciola hepatica

• Adult : i) large leaf-like fluke ii) brown to pale in colour iii) bilaterally symmetrical iv) life span about 10 years

• Eggs : i) large, yellowish brown ii) thin and smooth surface shell

Explain the mechanism of transmission of fasciola hepatica

• human become infected by ingesting metacercariae-contaminated vegetation

• after ingestion, metacercariae excyst in duodenum and penetrate through intestinal wall into peritoneal cavity

What are the clinical manisfestations/effects of fasciola hepatica during

1. early phase

2. chronic phase

• Early phase : i) inflammation, tissue destruction, allergic reactions ii) nonspecific signs/ symptoms : abdominal pain, nausea, vomitting

• Chronic phase : i) inflammation of bile ducts and also pancreas

What are the general characteristics of Liver Trematode : Fasciola gigantica?

• it is the largest human liver trematode

• more oblong with a longer posterior end than F. hepatica

• pathology, clinical features, diagnosis and treatment and control and preventive measures are similar to F.hepatica

What are the general characteristics of liver trematode : Clonorchis sinensis?

• important foodborne pathogen and cause of liver disease

• Disease : clonorchiasis

• transmission : ingestion of undercooked, salted, pickled or smoked freshwater fish containing metacercariae

Explain the general characteristics of adult and egg of Clonorchis sinensis

• Adult : i) flattened and leaf-shaped fluke ii) the body is slightly elongated and slender iii) 2 large branches of testes iv) lifespan about 25-30 years

• Eggs : i) small and oval in shape ii) yellowish brown

Explain the mechanism of transmission of Clonorchis sinensis

• human become infected by ingesting undercooked, salted, pickled, or smoked freshwater fish containing metacercariae

• after ingestion, metacercariae excyst in duodenum and ascend into the biliary tract

What are the clinical manisfestations/effects & s/s of clonorchis sinensis and Opisthorchis viverrine

• cause mechanical injury and bile duct obstruction

• symptoms : fatigue, anorexia, weight loss, diarrhea

• severe chronic disease results in obstructive jaundice

What are the general characteristics of Liver Trematode : Opisthorchis viverrine?

• adults live in biliary and pancreatic ducts

• disease : opisthorchiasis

• definitive host : humans and other mammals

• transmission : ingesting undercooked fish containing metacercariae

Explain the mechanism of transmission of Opisthorchis viverrine

• human become infected by ingesting undercooked fish containing metacercariae

• after ingestion, metacercariae excyst in duodenum and ascend into the biliary tract

What are the diagnosis for all the trematodes?

Identification of eggs in the feces

What are the treatment for all trematode?

Praziquantel

What are the prevention and control for all types of the trematodes?

• Fasciola gigantica & Fasciola hepatica & Fasciolopsis buski : Avoid eating raw water vegetables

• Opisthorchis viverrine & Clonorchis sinensis: Avoid from eating raw uncooked fish