Lecture 8 - Fascioliasis PDF

8th LECTURE  Causal Agents Fascioliasis is a parasitic disease caused by Fasciola hepatica and Fasciola gigantica, parasites of herbivores that can infect humans accidentally.  Systematic position Phylum: Platyhelminthes Class: Trematoda Genus: Fasciola 3 spe...

8th LECTURE  Causal Agents Fascioliasis is a parasitic disease caused by Fasciola hepatica and Fasciola gigantica, parasites of herbivores that can infect humans accidentally.  Systematic position Phylum: Platyhelminthes Class: Trematoda Genus: Fasciola 3 species can infect human: Fasciola hepatica Fasciola gigantica Fasciolopsis buski (live in small intestine of man)  Geographic Distribution Fascioliasis occurs worldwide in Europe, the Middle East, and Asia. Human infections with Fasciola are found in areas where sheep and cattle are raised. Geographic Distribution…… cont.  Morphology of the adult The adult is leaf-like, about 60 x 15 mm. It has an oral sucker and a larger ventral sucker Male reproductive system begins with two branched testes in the middle of the body The ovary is a branched (lobed) organ Reproductive Digestive system tract Morphology of the adult The ovum is: Size: about 150 x 80 µ. Shape: Operculated, oval in shape. Colour: Yellow in colour. Content: Contains immature embryo.  Life cycle The parasite lives in the bile ducts of man and herbivorous animals which are the definitive hosts. The ova pass with bile to the intestine to come out with faeces. In water, the ovum needs two weeks to mature and a miracidium come out. It swims in water until it finds the snail intermediate host Lymnaea cailliaudi. Inside the snail it metamorphoses into sporocyst then rediae and finally cercariae in about 6 weeks.  The cercariae swim in water and within 2 hours they settle on grass and water plants and even in water where they encyst forming encysted metacercariae )the infective stage). The encysted metacercaria can keep alive for about 6 months. The definitive host is infected by ingestion of vegetables or water containing the metacercariae. The cyst dissolves in the intestine and the young worm finds its way to the liver through the peritoneal cavity and reaches the bile ducts in about 6-8 week. Life cycle  Life Cycle Lymnaea cailliaudi  Mode of infection Humans can become infected by ingesting metacercariae-containing freshwater plants or metacercariae- contaminated water. Pharyngeal fascioliasis occur by eating raw infected liver.  Important points Definitive host: herbivorous animals and man Infection site: bile ducts Intermediate host: snail Lymnaea cailliaudi Infective stage: encysted metacercaria Diagnostic stage: eggs in stool Mode of infection: ingestion of encysted metacercaria in water or plants Infection rout: Oral  Clinical Features During the acute phase (caused by the migration of the immature fluke through the hepatic parenchyma), manifestations include: – abdominal pain, – hepatomegaly, – fever, vomiting, diarrhea, – eosinophilia, and can last for months. In the chronic phase (caused by the adult fluke within the bile ducts), the symptoms are: – biliary obstruction, – inflammation, – liver Rot. Liver Rot  Halzoun syndrome (Pharyngeal fascioliasis)  Occurring to people in countries in which eating raw infected liver is common (limited to the Middle and Far East).  The disease occurs due to adult Fasciola adhering to the posterior pharyngeal wall.  Halzoun syndrome is characterized by pharyngitis and laryngeal oedema.  Laboratory Diagnosis Microscopic identification of eggs in stool. Eggs can be detected in the stools or in material obtained by duodenal or biliary drainage.  Control & Prevention Treatment of infected animals. Snail control. Avoid eating raw vegetables before washing them. Avoid drinking infected (contaminated) water. Avoid eating raw liver to prevent halzoun syndrome  Learning outcomes By the end of the lecture, you should be able to: 1- Mention Causal Agent of Fascioliasis. 2- Mention systematic position of Fasciola spp. 3- Mention geographic distribution of Fascioliasis. 4- Enumerate Intermediate, Definitive and Reservoir hosts of Fasciola spp. 6- Explain life cycle of Fasciola spp. 7- Mention habitat of Fasciola spp. 8- Mention mode of infection by Fasciola spp. 9- Mention pathology and clinical features of Fascioliasis. 10- Diagnose Fascioliasis. 11- Enumerate disease control strategies  Suggested Reading http://www.dpd.cdc.gov/dpdx/HTML/Fasciolia sis.htm Chiodini, P.L.; Moody, A.H. and Manser,D.W. (2001): Atlas of Medical Helminthology and Protozoology. 4th ed. Churchill Livingstone, P. 32.