Lesson 4

• Trematodes


  Also known as "flukes" or "flatworms". Flukes are fleshy, leaf-shaped worms. They also have a digestive tract and two muscular suckers a.) Oral type which is the beginning of an incomplete digestive system and b.) Central sucker which serves for attachment.
• Tissue-dwelling Flukes


  Also known as "Asian Liver Fluke" and "Chinese Liver Fluke"
• Clonorchis Sinensis Lifecycle


  egg > snail (1st intermediate host) > release as larvae (cercariae) > eaten by fish (2nd intermediate host)> eaten by man as raw
• Clonorchis Sinensis


  • Found in Asia (Korea, China, Taiwan, Vietnam, Japan, and Asian Russia)
• Mode of Transmission for Clonorchis Sinensis

  Ingestion of undercooked or raw fresh water fish containing encysted larvae (metacercariae)
• Clonorchiasis


  • Most are asymptomatic
  • In heavy worm burden, fever, upper abdominal pain, anorexia, hepatomegaly, diarrhea, and eosinophilia may occur
  • Liver dysfunction may occur in chronic infection associated with heavy worm burden
• Laboratory Diagnosis for Clonorchis Sinensis

  Finding the characteristic eggs in stool specimen or duodenal aspirates
• Treatment for Clonorchis Sinensis

  • Praziquantel
  • Albendazole (Alternative)
• Prevention and Control for Clonorchis Sinensis

  • Thorough cooking of fish prior to consumption
  • Education of population re-eating habits
  • Stopping the seeding of fish culture ponds
  • Proper waste disposal to avoid contamination of water
• Fasciola Hepatica


  Also known as "Sheep Liver Fluke"
• Fasciola Hepatica Lifecycle


  egg> snail (1st intermediate host)> release as Cercariae > encyst in water plant (2nd intermediate host) > develop as metacercariae (infective stage) > eaten by man
• Fasciola Hepatica


  • Found worldwide especially in Asia, Europe, and the Middle East
• Mode of Transmission for Fasciola Hepatica

  ingestion of metacercariae encysted on edible aquatic plants like kangkong & watercress
• Fascioliasis or Sheep Liver Rot


  • Migration of the larval worm through the liver irritates the organ manifesting tenderness and hepatomegaly
  • Right upper quadrant pain, fever and chills, and marked eosinophilia
  • Hepatitis may develop with biliary obstruction
  • Some worms may cause necrotic foci in the liver
  • Ingestion of raw sheep liver may lead to temporary lodgment of the adult worm in the pharynx leading to suffocation
• Laboratory Diagnosis for Fasciola Hepatica


  • Finding eggs in stool specimen, the appearance of its eggs may be indistinguishable from the eggs of Fasciolopsis Buski. Examination of a sample of the patient's bile may aid in differentiation
  • Other tests may be performed such as ELISA and the Enterotest
• Treatment for Fasciola Hepatica

  • Dichlorophenol (bithionol)
  • Triclabendazole (Alternative)
• Prevention and Control for Fasciola Hepatica

  • Proper human waste disposal
  • Improvement of hygiene
  • Control of snail population
  • Avoidance of consumption of raw aquatic plants and contaminated water
  • Thorough washing and cooking of vegetables
  • Boiling of water in areas where the infection is endemic
  • Avoidance of ingestion of raw sheep liver
• Paragonimus Westermani


  Also known as "Oriental Lung Fluke"
• Paragonimus Westermani Lifecycle


  1. The first intermediate host is snail

  2. Second intermediate hosts are crab or crayfish
• Paragonimus Westermani


  • Occurs most commonly in Asian countries like China, Philippines, Japan, Vietnam, South Korea, Taiwan, and Thailand
  • Reservoirs are pigs, monkeys, and other animals that eat crayfish and crabs
• Mode of Transmission for Paragonimus Westermani


  Ingestion of undercooked or raw crab meat (crayfish) that contains the encysted larva (metacercariae)
• Paragonimiasis


  • Also called as "Pulmonary Distomiasis", "Endemic Hemoptysis", and "Parasitic Hemoptysis"
  • Early stages are usually asymptomatic
  • Patients may experience symptoms related to pulmonary involvement such as cough productive of blood-tinged sputum (hemoptysis), fever, and chest pain
  • Sputum has a foul, fishy odor and is most pronounced in the morning
  • Disease may mimic pulmonary tuberculosis
  • In rare cases, the immature flukes may migrate to the brain leading to cerebral paragonimiasis which manifest seizures, visual disturbances, and reduced motor skill precision
• Laboratory Diagnosis for Paragonimus Westermani


  • eggs in the sputum or feces
  • Chest x-ray shows a ring shadowed opacity with cavitation that gives appearance to bunch of grapes
• Treatment for Paragonimus Westermani

  • Praziquantel
  • Bithionol (alternative)
• Prevention and Control for Paragonimus Westermani

  • Adequate and thorough cooking of freshwater crabs or crayfish
  • Health education
  • Control of snail population
  • Elimination of reservoir hosts
  • Treatment of infected persons
• Fasciolopsis Buski


  Also known as "Large Intestinal Fluke"
• Fasciolopsis Buski Lifecycle


  1. First intermediate host is snail

  2. Second intermediate host are edible aquatic plants (e.g., watercress and lotus)
• Fasciolopsis Buski


  • It is the largest intestinal fluke that can infect humans
  • Infection is common in Asia and the Indian subcontinent
• Mode of Transmission for Fasciolopsis Buski

  Ingestion of raw or inadequately cooked aquatic vegetation that carries encysted metacercariae
• Fasciolopsiasis


  • Most are asymptomatic
  • With heavy worm burden, abdominal discomfort with inflammation and bleeding in infected area may occur
  • Ulcerations may occur and symptoms may mimic those of duodenal ulcer
  • Malabsorption
  • Allergic symptoms such as edema of the face, abdominal wall, and lower limbs
  • Profound intoxication may lead to death
• Laboratory Diagnosis for Fasciolopsis Buski


  • Demonstration of eggs in stool specimen
  • Examination of samples and duodenal aspirates may help differentiate F. buski eggs and F. Hepatica
• Prevention and Control for Fasciolopsis Buski

  • Adequate washing and cooking of aquatic plants before consumption
  • Proper disposal of human waste
  • Control of snail population
  • Treatment of infected persons
• Schistosoma spp.


  Blood-dwelling Flukes
• Schistosoma spp.


  • Blood flukes are dioecious
  • They are known as "romantic parasites" since the male and female worms are usually in a state of copulation or en copula
  • Female worms are usually larger than male worms
  • They are obligate intravascular parasites
  • Reservoirs are domestic animals such as water buffalo and pigs
  • There are 3 types of Schistosoma spp.: S. Mansoni, S. Japonicum, S. Haematobium
• Mode of Transmission for Schistosoma spp.

  Skin penetration by the fork-tailed cercaria (larval form)
• Schistosomiasis (Bilharziasis)


  • Asymptomatic infection (Most common form of infection, Chronic infection may become symptomatic)
  • Early Acute Infection (Pruritic papules seen at the site of entry which is called "swimmer's itch" or "clam digger's itch", Followed after 2-3 weeks by fever and chills, abdominal pain, cough, bloody diarrhea, and weight loss, Dysuria and hematuria may occur in patients infected with S. Haematobium)
  • Katayama Fever (Systemic hypersensitivity reaction to the migrating schistosomes usually associated with S. Japonicum, Rapid onset of fever, myalgia, body malaise, cough, diarrhea, and eosinophilia occurring 1-2 months after exposure to the parasite, Lymphadenopathy and hepatosplenomegaly may also occur, It can lead to hepatic dysfunction leading to portal hypertension, The most common cause of death is internal bleeding from ruptured esophageal varices)
  • Associated Conditions (Include development of nephrotic syndrome in S. Japonicum and S. Haematobium, Repeated Salmonella infections from infection with S. Mansoni and S. Japonicum, Development of Hepatocellular Carcinoma or liver cancer is associated with S. Japonicum, Development of cancer of the urinary bladder is associated with S. Haematobium)
• Laboratory Diagnosis for Schistosoma spp.

  • Demonstration of eggs in the feces or rectal biopsy specimen for S. Mansoni or S. Japonicum or urine for S. Hematobium
  • S. mansoni eggs have a large lateral spine
  • S. Japonicum eggs have rudimentary spine
  • S. Haematobium have large terminal spines
• Treatment for Schistosoma spp.

  • For all three species: Praziquantel
  • S. Mansoni alternative drug: Oxamniquine
  • Anti-Malaria drugs such as artemether and artemisinins are also proven effective
• Prevention and Control for Schistosoma spp.

  • Control of transmission through snail control
  • Health education
  • Provision of sanitary facilities and water supply
  • Control of disease
  • Chemotherapy using praziquantel is the main thrust of the Philippine program for schistosomiasis control (DoH)
  • Prevention of swimming in endemic areas
• Cestodes


  • Also known as "tapeworm" or "flatworm"
  • Classified under the subkingdom Metazoa, phylum Platyhelminthes
  • These parasites are considered as primitive worms
  • They do not possess a digestive system nor a nervous system
  • They consist of three regions: Head or Scolex (Scoles which may consist of either books, suckers, or sucking grooves), Neck (region of growth and connects the head to the body of the), and Body (consists of a series of segments called proglottids)