Helminths (Trematoda) Assis.Prof.Dr. Suhad Faisal Hatem

Helminths (Trematoda) Helminth: commonly known as parasitic worms, are large multicellular organisms, which when mature can generally be seen with the naked eye including  two-phyla: 1. Phylum: Platyhelminths (flat worms) 2. Phylum: Nemahelminths or Nematoda (true round worms). Platyhelminths includes: 1-Class: Trematoda ) Flukes( 2-Class: Cestoda ) Tape worms( 3- Turbellaria Trematoda class also classified to groups according to the presence of the adult fluke in the host's body into:   1. Liver (or hepatic) flukes, ex: Fasciola hepatica . Clonorchis sienensis 2. Intestinal flukes ex: Fasciolopsis buski, Heterophyes heterophyes 3. Blood flukes, ex: Schistosomes 4. Lung flukes, ex: Paragonimus westermani

Morphology and anatomy of Fasciola hepatica Fasciola hepatica is one of the largest flukes of the world, reaching a length of 30 mm and a width of 13 mm, Fasciola gigantica, on the other hand, is even bigger and can reach up to 75 mm). It is leaf-shaped, pointed at the back (posteriorly) and wide in the front (anteriorly). The oral sucker is small but powerful and is located at the end of a cone-shape projection at the anterior end. The acetabulum is a larger sucker than the oral sucker and is located at the anterior end. Adults of liver flukes are localized in the liver of various mammals, including humans.These flat worms can occur in bile ducts, gallbladder, and liver parenchyma. They feed on blood. Adult flukes produce eggs which are passed into the intestine. It depends on intermediate host (a snail) to complete its life cycle. The intermediate host is the Lymnaea genus of snail which lives in marshy areas and standing water. Fasciolosis: is a parasitic worm infection caused by the common liver fluke Fasciola hepatica as well as by Fasciola gigantica.

Pathogensis Acute fascioliasis The acute clinical syndrome of Fasciola hepatica infection occurs during migration of the fluke larvae to the liver parenchyma, with resultant inflammation and localized destruction of liver cells. Once in the bile ducts, liver flukes of all species produce inflammation due to mechanical irritation and toxic secretions. In its severe form it occurs in sheep but rarely in man and requires large numbers of parasites, usually over 10,000, to be ingested. Large numbers of migrating larvae invade the liver and cause a traumatic hepatitis that is frequently fatal. Sometimes the liver capsule may rupture into the peritoneal cavity, causing death from peritonitis. More usually the invasive phase lasts many weeks, with the most common symptoms being intermittent fever, hepatomegaly, and abdominal pain, malaise, wasting, urticaria and eosinophilia are usual.

Chronic fascioliasis This phase may develop months or years after initial infection, when the infection is asymptomatic. Adult flukes in the bile ducts cause inflammation and hyperplasia of the epithelium. The resulting cholangitis and cholecystitis, combined with the large body of the flukes, are sufficient to cause mechanical obstruction of the biliary duct.This lead to biliary colic, epigastric pain, fatty food intolerance, nausea, jaundice, pruritus, right upper-quadrant abdominal tenderness. Hepatic enlargement may be associated with an enlarged spleen or ascites Chronic inflammation is connected to increased cancer rates.

Diagnosis 1- By finding yellow-brown eggs in the stool.The eggs pass through the body and out via the faeces. 2-An enzyme-linked immunosorbent assay (ELISA) test is the diagnostic test of choice. ELISA is available commercially and can detect anti-hepatica antibodies in serum and milk; Proteases secreted by F. hepatica have been used experimentally in immunizing antigen. 3- Radiological methods can detect lesions in both acute and chronic infection, while laparotomy will detect lesions and also occasionally eggs and live worms. 4-biopsy of liver, and gallbladder punctuate can also be used. Treatment 1-Triclabendazole 2-protein-rich diet are recommended. Iron and vitamins may be required.

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