Parasitic Helminths: Phylum Platyhelminthes and Cestodes
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Questions and Answers

What is the primary mode of transportation of Ascaris lumbricoides eggs?

  • Poor sanitation
  • Flies transporting eggs on their legs (correct)
  • Infected human carriers
  • Contaminated water
  • What is the method of transmission of Trichuris trichiura?

  • Direct contact with infected humans
  • Vectors such as flies and mosquitoes
  • Skin penetration of larvae
  • Ingestion of embryonated eggs through contaminated food (correct)
  • What is the definitive host of Trichuris trichiura?

  • Flies
  • Humans (correct)
  • Pigs
  • Chickens
  • What is the symptom of Trichuris trichiura infection that is often associated with large infections?

    <p>Rectal prolapse</p> Signup and view all the answers

    What is the diagnostic method for Trichuris trichiura infection?

    <p>Bipolar eggs in feces</p> Signup and view all the answers

    What is the treatment for Ascaris lumbricoides infection?

    <p>Mebendazole</p> Signup and view all the answers

    What is the primary prevention method for Ascaris lumbricoides infection?

    <p>Proper sanitation</p> Signup and view all the answers

    What is the geographic distribution of Trichuris trichiura?

    <p>Cosmopolitan</p> Signup and view all the answers

    What is the characteristic of nematodes?

    <p>They have a full digestive system</p> Signup and view all the answers

    What is the symptom of Ascaris lumbricoides infection that is related to the lungs?

    <p>Ascaris pneumonitis</p> Signup and view all the answers

    Study Notes

    Parasitic Helminths Overview

    • Phylum Platyhelminthes encompasses three major groups: Cestodes (Tapeworms), Trematodes (Flatworms), and Nematodes (Roundworms).
    • Approximately half of the helminth species are parasitic, many being significant human pathogens.
    • Parasitic forms exhibit complex reproductive cycles involving multiple life stages and various hosts.

    Cestodes (Tapeworms)

    • Mature tapeworms possess both male and female reproductive organs.
    • Life cycle involves an intermediate host and definitive host.
    • Notable species include:
      • Diphyllobothrium latum (fish tapeworm)
      • Taenia saginata (beef tapeworm)
      • Taenia solium (pork tapeworm)

    Taenia solium (Pork Tapeworm)

    • Definitive Host: Humans
    • Intermediate Host: Pork
    • Geographic Distribution: Cosmopolitan
    • Transmission: Ingesting undercooked pork.
    • Symptoms:
      • Adult form causes verminous intoxication.
      • Larval form leads to cysticercosis.
    • Treatment Options: Praziquantel, surgical intervention.
    • Diagnosis: Identification of eggs and proglottids in feces, ELISA, X-rays, or MRI.

    Diphyllobothriid Sp. (Broad Fish Tapeworm)

    • Definitive Hosts: Fish-eating carnivores (humans, dogs, bears, seals).
    • Intermediate Host: Crustaceans (first), fish (second).
    • Geographic Distribution: Worldwide, particularly in areas where raw fish consumption is common.
    • Transmission: Consumption of infected hosts.
    • Symptoms: Adult form causes nausea, diarrhea, and weakness (diphyllobothriasis); larvae can cause sparganosis via contaminated water or eggs.
    • Treatment: Praziquantel and surgical intervention for sparganosis.
    • Diagnosis: Detection of eggs and proglottids in feces, X-rays or MRI.
    • Prevention: Maintain proper hygiene and avoid raw or undercooked fish.

    Trematodes (Flatworms)

    • Trematodes have male and female sexual organs within the same organism; some require secondary hosts.
    • Examples include:
      • Schistosoma japonicum
      • Aspidogaster conchicola
      • Paragonimus westermani

    Schistosoma japonicum (Bilharziasis)

    • Definitive Hosts: Humans and various wild mammals (dogs, cats, deer, primates).
    • Intermediate Host: Aquatic snails.
    • Geographic Distribution: Southeast Asia.
    • Transmission: Cercaria penetrate the skin during contact with contaminated water.
    • Symptoms: Causes Schistosomiasis characterized by three phases: migratory, acute, and chronic.
    • Treatment: Praziquantel.
    • Diagnosis: Identification of eggs in feces, ELISA.
    • Prevention: Proper sanitation, controlling snail populations, and avoiding contact with contaminated water.
    • Status in the Philippines: Infection rates decreased from 10.4% (1981-1985) to 4.1% (1996) due to mass treatment, environmental sanitation, snail control, and education initiatives.

    Other Schistosoma Species

    • Schistosoma haematobium
    • Schistosoma mansoni

    Paragonimus westermani

    • Definitive Hosts: Humans and various fish-eating mammals.
    • Intermediate Hosts: Aquatic snails (first), freshwater crabs and crayfish (second).
    • Geographic Distribution: Asia and Oceania.
    • Transmission: Ingestion of undercooked crustaceans.
    • Symptoms: Causes a disease known as Paragonimiasis.

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    Description

    Learn about the three major groups of parasitic helminths, including tapeworms, flatworms, and roundworms. Discover the complex reproductive cycles and life stages of these pathogens, and explore examples of cestodes and their hosts.

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