Platyhelminths as Human Parasites

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Platyhelminths as Human Parasites

• Images from the CDC

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Trematode Parasites

• Clonorchis sinensis
• Fasciola hepatica
• Schistosoma spp.
• mansoni
• japonicum
• Haematobium
• Paragonimus westermani
• Dicrocoelium dendriticum

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Clonorchis sinensis

• Chinese Liver Fluke
• 20 Million Infected People
• Infection by eating raw or udercooked fish
  (pickled fish)
• Flukes live in bile ducts
• Symptoms
• Pain in upper rt. Quadrant
• Hepatosplenomegaly
• Gall Stones
• Obstructive Jaundice
• Bile Duct Cancer

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Clonorchis sinensis
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Fasciola hepatica

• Sheep Liver Fluke
• Human infection from eating wild aquatic plants
• Symptoms
• Hepatosplenomegaly
• Anemia
• Jaundice
• Abdominal Pain
• Fatty Food Intolerance

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Schistosoma spp.

• Dioecious
• Large males with split bodies forming a
  longitudinal groove
• Females housed in groove of male
• Adults may live for 10-30 years

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Schistosoma spp.

• Schistosoma mansoni
• Egg with large subterminal spine
• Adults in veins of large intestine
• Schistosoma japonicum
• Egg with diminutive subterminal spine
• Adults in veins of small intestine
• Schistosoma haematobium
• Egg with terminal spine
• Adults in veins of urinary bladder

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Schistosomiasis
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Intermediate Hosts of Schistosomes

• Schistosoma mansoni
• Africa, S. America, West Indies
• Int. Host - Biomphalaria
• Schistosoma japonicum
• Asia
• Int. Host - Oncomelania
• Schistosoma haematobium
• Africa
• Int. Host - Bulinus

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Schistosome Cercaria

• Cercariae penetrate skin of definitive host
• Schistosomes that normally parasitize birds may
  produce the rash known as swimmers itch. The
  rash is the result of an immune response to the
  cercariae.

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Schistosomiasis

• Blood Flukes
• 200 Million people infected in Africa and Asia
• Symptoms
• Ascites
• Symmers Fibrosis
• Death via hemorrhage

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Control of Schistosomes

• Proper disposal of body waste
• Avoid contact with contaminated water
• Vaccine?
• Biological Control?
• Aswan High Dam
• Electricity
• Agriculture
• Schistosomiasis

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Paragonimus westermani

• Lung Fluke
• Widely Distributed
• gt10 million people infected in China
• Infection by eating raw or undercooked
  crustaceans
• Symptoms
• Chronic Cough
• Purulent, blood-streaked sputum
• Jacksonian Epilepsy, meningitis (cerebral
  infection)
• Death (pericardial infection)

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Dicrocoelium dendriticum

• Liver fluke of livestock
• Humans are accidental hosts
• Mind-controlling effect on ants

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Cestode Parasites

• Taenia saginata
• Taenia solium
• Diphyllobothrium latum
• Echinococcus spp.

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Taenia saginata

• Beef Tapeworm
• Cows are intermediate host
• Scolex without hooks
• Motile proglottids

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Taenia solium

• Pork Tapeworm
• Pigs are intermediate host
• Scolex with hooks

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Taeniasis
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Diphyllobothrium latum

• Broad Fish Tapeworm
• Single worms up to 20 meters
• Most severe adult tapeworm disease
• Vitamin B12 absorption by worms leads to anemia

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Diphyllobothriasis
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Cysticercosis

• Infection by juvenile tapeworms
• Symptoms related to location of cysticerci
• Brain
• Eyes
• Heart

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Echinococcus spp.

• Hydatid Disease
• Infection by close contact with sheep dogs
• Cysts may grow for many years
• Surgical removal after scolicidal flush

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