Fasciola hepatica and F. gigantica are bile duct parasites of domestic ruminants.In their life cycle freshwater snails act as intermediate host Humans become accidentally infected when they eat plants to which infectious parasite stages (metacercariae) adhere Dicrocoelium dendriticum is a bile duct parasite in sheep, cattle, and other herbivores, Its life cycle includes two intermediate hosts (terrestrial snails and ants). Humans become infected accidentally when they ingest ants containing infective metacercariae of the lancet liver fluke. Fasciola hepatica F. hepatica is a flattened, leaf-shaped parasite about 2–5 cm long and at most 1 cm wide. Dicrocoelium dendriticum The lancet liver fluke (0.5–1.0 ! 0.2 cm)
Life cycle of Fasciola hepatica Adult liver flukes parasitize in the bile ducts. They produce large golden brown, operculated eggs that are shed by the bile duct-intestinal tract route. Under favorable conditions, a ciliate larva, the miracidium, develops in the egg within a few weeks. The miracidia then hatch and penetrate into freshwater snails where they transform into sporocysts.
Life cycle of Fasciola hepatica After formation of further asexual reproductive stages, tailed cercariae develop and swarm out of the snails into the open water. They soon attach to plants and encyst, transform into infective metacercariae, which are then ingested with vegetable food of their definitive hosts. Eating watercress contaminated with metacercariae is one of the sources of infection for humans.
Life cycle of Fasciola hepatica The juvenile liver flukes hatch from the cyst in the small intestine, penetrate the intestinal wall, and migrate through the peritoneal cavity to the liver. After migrating through the hepatic parenchyma for about six to seven weeks, the parasites finally reach the bile ducts, in which they develop to sexual maturity. Egg excretion begins two to three months
Life cycle of Life cycle of Dicrocoelium dendriticum It stands apart from most trematodes since it has a land based life cycle. The definitive host's feces contain miracidia which do not hatch until after they are eaten by the first intermediate host, a land snail, The miracidium emerges inside the intestine of the snail and metamorphoses into a sporocyst and than into cercaria. The second intermediate host is the common brown ant, There cercaria turns to metacercaria. Upon ingestion by the definitive host, the metacercaria arrive in the duodenum and migrate up the common bile duct to the liver. The adult fluke matures in 6-7 weeks, producing egg capsules about a month later. producing egg capsules about a month later.
Fasciola hepatica Eating watercress contaminated with metacercariae is one of the sources of infection for humans. Dicrocoelium dendriticum Humans become infected accidentally when they ingest ants containing infective metacercariae of the lancet liver fluke. Such infections are rare and either run an asymptomatic course or manifest in mild abdominal and hepatic symptoms.
Fasiola hepatica in liver Fasiola hepatica in liver Fasiola hepatica in liver
Diagnosis of Fasciola infection. The manifestations to be expected during the migration phase of the liver fluke include mainly leukocytosis, eosinophilia, and a rise in liverspecific serum enzymes. Detection of eggs in stool or duodenal fluid is not possible until at least two to three months. Other diagnostic tools include detection of serum antibodies and of coproantigen in stool. Diagnosis of Dicrocoelium infection. Diagnosis is based on detection of eggs in stool (about µm, oval, dark brown containing a miracidium with two rounded germinal cells) Ingestion of contamined beef or mutton liver can result in egg excretion in stool without infection.This is intestinal passage.
Treatment of Fasciola infection The drug of choice is triclabendazole, the infection can be avoided by not eating raw watercress and other plants that may be contaminated with metacercariae. Treatment of Dicrocoelium infection Praziquantel has been shown to be effective against Dicrocoelium in animals.
Clonorchis spp Liver flukes of the genera Clonorchis occur mainly in river and lake regions of Asia and Eastern Europe. The definitive hosts of Clonorchis species are fish eating mammals like cats,dogs, pigs, and humans,in which these trematodes colonize the bile ducts.
Clonorchis spp The life cycle of these organisms involves various species of aquatic snails as the first intermediate hosts and freshwaterfish species as the second intermediate hosts. The infective metacercariae are localized in the musculature of the fish and,when raw fish is ingested, enter the intestinal tract of the definitive host, they migrate through the common bile duct
Clonorchis spp egg
Clonorchis spp Pathogenesis and clinical manifestations. Clonorchis infections cause proliferations of the bile duct epithelium, cystlike dilatation, inflammation,and fibrosis of the bile duct walls as well as connective tissue proliferation in the hepatic parenchyma. A high incidence of bile duct carcinomas has been reported from areas in which C. sinensis are endemic. Clinical symptoms of more severe infections include variable fever, hepatocholangitic symptoms with hepatomegaly, leukocytosis, upper pains, and diarrhea.
Clonorchis spp Diagnosis, therapy, and prevention Diagnosis is made by detection of eggs (26–32 lm long) in stool or duodenal fluid Therapy and prevention The drug of choice is praziquantel; albendazole can also be used. Reliable preventive measures include boiling or frying fish to kill the metacercariae, which die at temperatures as lowas 70 C, and freezing to –10 8C for five days.
Paragonimus sp (Lung Flukes) Lung flukes of the genus Paragonimus are endemic in parts of Asia, Africa, and America. Parasitize in pulmonary cysts and cause a tuberculosis-like clinical picture. Following development in two intermediate hosts(freshwater snailsband crabs or crayfish), infective stages (metacercariae) can be transmitted to humans by eating the crabs or crayfish uncooked. Parasite eggs are detectable in sputum or stool.
Paragonimus sp (Lung Flukes) The sexually mature parasites live in cystlike dilatations in the lungs,usually in connection with the bronchial tree. The yellow-brown, operculated eggs laid by the adultworms are shed either in sputum or stool.
Paragonimus sp.adult and egg egg egg Adult egg
Paragonimus sp (Lung Flukes) The life cycle then continues in water, where a miracidium develops in each egg, hatches and invades an intermediatebhost. Egg-shaped cercariae with short tails develop in the first intermediate host, a freshwater snail. The cercariae encyst in the second intermediate host like crayfish or crabs to form the infective Metacercariae.
Paragonimus sp When a suitable definitive host ingests the crustaceans uncooked, the young trematodes hatch in the small intestine,migrate through the peritoneal cavity to the diaphragm and finally into the lungs. The prepatent period is two to three months. Parasites that deviate from the normal migration route may enter other organs.
Paragonimus sp Besides humans, crustacean eating mammals play a significant epidemiological role as reservoir hosts. Young lung flukes can be localized in the musculature of pigs and other “transport hosts” and be transmitted to humans who ingest the raw meat of these animals.
Clinical manifestations. Typical cases are clinically characterized by pulmonary symptoms chronic cough, bloody expectoration, thoracic pain. Parasites following the normal or deviant migration routes can also cause abdominal,hepatic, pancreatic or CNS symptoms, or skin lesions like swelling, nodules. Paragonimus sp
Diagnosis, therapy, and prevention. An etiological diagnosis is based on detection of eggs in sputum or stool and of serum antibodies. Regarding the differential diagnosis especially tuberculosis must be kept in mind. The drug of choice is praziquantel, but triclabendazolem can also be used. Cooking crustaceans before eating them is a reliable preventive measure. Paragonimus sp