nematodes

• life cycle consist of three stages: embryonated egg (ova), larva, adult worms
• the body covering is called that cuticle
• digestive system of nematodes consist of three structures

  • stomodeum - mouth, esophagus, buccal cavity
  • intestine
  • anus - proctodeum
• ascaris lumbricoides (large intestinal roundworm)

  • largest and most common helminth infection
  • ingestion of food or water contaminated with human feces containing infective embryonated ova
  • localized in lungs and migrate into bronchioles
  • coughed up and swallowed
  • matures in the small intestine (produces little damage)
  • loffler syndrome
  • can lead to pneumonia
  • effective drugs: mebendazole, albendazole, pyrantel pamoate
• enterobius vermicularis (pinworm or seatworm)

  • ingestion of eggs of the worm
  • matures in large intestine
  • migrates to perianal region if female gets impregnated
  • autoinfection occurs with hand to mouth transmission
  • manifested with pruritis ani
  • drug of choice: albendazole, mebendazole, pyrantel pamoate
• trichuris trichiura (human whipworm)

  • ingestion of food or water contaminated with human feces contaning infective eggs
  • migrates to colon where maturation and mating occurs
• trichuris trichiura: trichuriasis

  • chronic dysentery, anemia, rectal prolapse
  • drug of choice: mebendazole or albendazole
• ancylostoma duodenale (old world hookworm) and necator americanus (new world hookworm)

  • share the same four stages in life cycle: eggs, rhabditiform larvae, filariform larvae, adults
  • rhabditiform larva - immature, newly hatched larva
  • filariform larva - non-feeding, infective larva
• n. americanus - buccal capsule equipped with pair of cutting plate

  a.duodenale - consist of teeth
• hookworm infection

  • skin penetration produces pruritic papule or vesicle (ground itch)
  • recommended drug: mebendazole and pyrantel pamoate
• strongyloides stercoralis (threadworm)

  • infective stage is the filariform larva
  • two distinct life cycle: within the host and a free living in soil
  • acquired through direct skin penetration - beginning of human cycle
  • acquired through indirect mode - free living cycle that occurn in soil
  • acquired through autoinfection
  • drug of choice: ivermectin
  • alternative drug: thiabendazole and mebendazole
• strongyloidiasis (cochin china diarrhea)

  • skin irritation at site of entry is seen
  • lungs (pneumonitis) > intestine (diarrhea and abdominal pain)
  • can stimulate allergic reaction
  • can lead to steatorrhea
• capillaria philippinensis (pudoc worm)

  • migratory fish eating birds are the natural host
  • intestinal capillariasis: abdominal pain with borborygmus and chronic idarrhea
  • drug of choice: aldendazole