Strongy

• Strongyloides stercoralis

  Has two components: The free living cycle, The parasitic cycle

  
• Strongyloides stercoralis is considered a facultative parasite as it can exist as a parasite to humans and as a free living organism

  
• Strongyloides stercoralis life cycle

  1. Free-living cycle: Rhabditiform larvae passed in stool develop into infective filariform larvae or free-living adult males and females that mate and produce eggs

  2. Parasitic cycle: Filariform larvae penetrate human skin, migrate to small intestine, molt into adult female worms that produce rhabditiform larvae which can cause autoinfection

  
• Rhabditiform larvae passed in stool are the diagnostic stage
• Rhabditiform larvae in environment with scarce nutrients

  Develop into filariform larvae

  
• Rhabditiform larvae in environment with abundant nutrients


  Develop into free-living adult males and females
• Parasitic cycle


  Filariform larvae penetrate skin, enter circulation, migrate to lungs, are coughed up and swallowed, molt into adult female worms in small intestine

  
• Only female adult worms exist in human host, reproducing parthenogenetically
• Adult female worms in intestinal mucosa

  Produce embryonated ova that hatch into rhabditiform larvae

  
• Rhabditiform larvae in intestine

  Can transform into infective filariform larvae that penetrate intestinal wall and autoinfect host

  
• Strongyloides stercoralis is the first intestinal nematode that can demonstrate autoinfection

  
• Adult female Strongyloides stercoralis

  • Have uteri intertwined with esophagus, appearing like intertwined threads - hence the name "threadworm"
• Pathology of Strongyloides stercoralis infection

  • Skin invasion by filariform larvae
  • Larval migration, particularly to lungs
  • Intestinal penetration by adult female worms

  
• Larva currens


  Erythematous serpiginous skin lesions at site of filariform larva entry, with pruritus and urticaria

  
• Larval migration can cause lobar pneumonia with hemorrhage, cough, and tracheal irritation
• Strongyloides infection in a cat


  • Destruction and atrophy of intestinal villi, adult worms embedded in intestinal mucosa

  
• Tracheobronchial tree


  1. Laryngopharynx

  2. Swallowed
• Larvae of worm (Strongyloides sterocralis) within the ileal fluid, entering the ileal mucosa

  
• These worms can embed themselves from the pylorus of the stomach down to the rectum, but most of the time they are found in the small intestine

  
• Ground itch


  vs Larva currens

  
• There is a destruction and atrophy of the finger like projections of the small intestine, which are called villi
• With the loss of these villi, there would be an effect on the absorption and digestion of nutrients
• Strongyloides infection in a cat


  • Presence of nodules in the small intestine
• Light infection


  Does not cause intestinal symptoms
• Moderate infection


  Causes diarrhea alternating with constipation
• Heavy infections


  Produce intractable, painless and intermittent diarrhea (Cochin-China diarrhea)
• Chronic Strongyloidiasis


  • Often asymptomatic
  • Episodes of vomiting, diarrhea and constipation
  • Recurrent asthma
• If not diagnosed properly and managed properly, these patients can lead to emaciation, loss of appetite, GIT bleeding, anemia, intestinal obstruction, and malabsorption leading to cachexia
• In the presence of females on the walls of the intestine, there could be a loss of the peristaltic movement so that can later cause intestinal obstruction, malabsorption can also occur
• With the loss of the villi or atrophy of the villi, it should raise the suspicion that the patient could be having infection by Strongyloides sterocralis
• The filariform larvae that penetrated the intestinal wall will have larval lung migration aside from GIT symptoms, the patient will have left flurry syndrome or recurrent asthma
• Hyperinfection


  A syndrome of accelerated autoinfection that occurs with immunocompromised patients
• If the patient is immunocompromised brought about by chemotherapy, radiation therapy, or untreated HIV, the immune system is down and it's now easy for the rhabditiform larva to become the filariform larva, thus accelerating autoinfection
• Hyperinfection


  • Exacerbation of gastrointestinal and pulmonary symptoms
  • Increased number of larvae in stool and even in sputum
• Rhabditiform larva


  The diagnostic stage for Strongyloides, as the egg hatches inside the human intestine

  
• Even if the ova of Strongyloides stercoralis are not seen in the stool, it's very important to take note that they look similar to the hookworms, with thin shells and cleaved embryos

  
• Rhabditiform larvae

  Short and stout
• Filariform larvae

  Slender and long, the infective stages

  
• The buccal cavity of the rhabditiform larva of Strongyloides stercoralis is short, but they have prominent genital primordium
• Strongyloides stercoralis life cycle

  1. Free-living cycle: Rhabditiform larvae passed in stool, develop into infective filariform larvae or free-living adults that mate and produce eggs, which hatch into rhabditiform larvae that become infective filariform larvae

  2. Parasitic cycle: Filariform larvae penetrate human skin, migrate to small intestine, molt into adult female worms that produce eggs yielding rhabditiform larvae, which can cause autoinfection