Phylum Platyhelminthes By : dr. sadiq al-shaikh

Class Trematoda Subclass Digenea ( The trematodes with 2 generations in their life cycle ) indirect life cycle . Subclass monogenea (Direct life cycle with one generation in their life cycle ex. Fish infection .

General characters of Digenetic trematodes : 1 – Leaf – like shaped unsegment, flat worms called Flukes. 2 – Size varies from 1 MM to several centimeters. 3 – The organs of attachment are two suckers oral and ventral suckers the last one known as acetabulum.

4 – Sexes are not separated , each worm is a hermaphrodite (Monoecious ), except the Schistosomes ( Dioecious ). 5 – Body cavity is absent. 6 – Alimentary canal is present , but incomplete the anus is absent. 7 – Excretory and nervous system are present .Excretory system consist of flame cells and collecting tubules which open posteriorly in to excretory pore.

8 – Reproductive system is highly developed 8 – Reproductive system is highly developed. 9 – The worms are oviparous and the eggs with operculum except that of the Schistosoma .

FOUR KINDS OF FLUKES ARE PRESENT THESE ARE LIVER FLUKES : ex. Fasciola hepatica ,Fasciola gigantica and Clonorchis sinusis . INTESTINAL FLUKES : EX . Fasciolopsis buski ( Giant intestinal fluke ) and Heretrophyes heterophyes . LUNG FLUKES : ex . Paragonimus westermani . BLOOD FLUKES Schistosoma spp .

LIVER FLUKES Fasciola hepatica It is known as sheep liver fluke. This disease is world –wide in distribution. The parasite infects herbivorous animals like sheep ,goat and cattle and occasionally Man .

Morphology : The adult worm is large leaf –like , unsegmented , 3 cm in length and 1.5 cm in breadth and brown or grey in colour , there are 2 suckers, The oral sucker is smaller than the ventral .The intestinal caeca is highly branched.

Life span in sheep is 5 years and in man about 10 years. The ova is large, ovoid in shape brownish – yellow in colour. Measuring 140 M by 80 M , and it is operculated. Excreted with the bile to the duodenum and intestine and the faece.

Life Cycle Definitive host: Sheep, Goat, Cattle and Man, Sheep is considered the reservoir host for the infection.

Intermediate host : Snail of the genus Lymnaea 1- The eggs pass out in the faeces of the definitive host , mature in water and from each egg a ciliated miracedium will be developed in 2 – 3 weeks . 2- The miracedia enter the body of the intermediate host ( Snail of the genus Lymnaea ) .

3- Inside this host the miracedia pass through the stages of Sporocyst , 2 generations of Redia and finally to Cercaria. The whole cycle takes from 1 – 2 month. 4- The cercaria after leaving the snail swim in the water and encyst on grasses and water plants forming Metacercaria .

5- The Metacercaria will be swallowed with the grass by the definitive host: sheep , goat , cattle and occasionally Man . 6- On entering the digestive tract , the Metacercaria excysts in the duodenum and migrate through intestinal wall to the peritoneal cavity and enter the liver capsule and settle in the bile ducts of the liver and develop to adult worms .This takes about 3 months .

Pathogenicity Infection of the liver with F. hepatica is known ( liver Rot ) Fascioliasis is prevalent in sheep ,goat and cattle in the middle and south parts of Iraq and to less extent in the north , heavy infection now a day in man reported in Iraq . The infection causes great loss and mortality especially among sheep, goat and less in cattle.

Heavy infection of the liver causes liver cirrhosis and damage to the liver tissue. It was once primarily thought of, as Veterinary problem but it has been estimated that 17 million people are infected and that 180 million are at the risk of infection.

The pathogen is wide spread, all over the world The pathogen is wide spread, all over the world. Infection begins with consumption of water plants or bad or not washed vegetables.

Disease signs and symptoms in man Fascioliasis occurs in two stages: The first stage: larval period is marked clinically by abdominal pain, fever, weight loss and articaria . Eosinophilia and elevations in liver transaminase. This stage can last for several months. Egg production during this stage is minimal.

The second stage : refers to biliary period, represents the maturation of larvae in to adult flukes that pass in to the biliary ducts. Symptoms during this phase are often subtle, vague and even asymptomatic. Patients may develop intermittent right upper quadrant pain, which can mimic cholecystitis . Ova are released.

Complications from chronic disease include anemia, cholangitis, biliary obstruction, jaundice and liver cirrhosis. Subcapsular liver hematomas and hemoperitoneum are also reported. Ectopic sites include inguinal lymph nodes, subcutaneous skin , brain and eyes infection , no potential for malignancy of the biliary tract .

Diagnosis General stool examination by finding the eggs. Radiological examination X –Ray. Ultrasound ,and CT scan . ELISA.

Treatment Triclabendazole , abenzimidazole is the first line treatment 10 mg / kg B.W. as a single dose . For more severe disease, an additional dose can be taken 12 hours later.

Prevention and Prophylaxis - Early detection of the infection. - Public health measures and health care workers. - Improving sanitation, decreasing outdoor defecation. - Improvement of inspection and transport of vegetation.

-Shedding of viable eggs. -Control snail populations -Shedding of viable eggs. -Control snail populations. -Routine treatment of livestock .

Fasciola gigantica Another species of Fascioliasis prevalent in Iraq . Life cycle and hosts similar to that of F. hepatica.