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Introduction
  • Classification
    • Helminths infections include
      • tapeworms (cestodes)
      • flukes (trematodes)
      • roundworms (nematodes) (this topic)
        • roundworms are broken down into
          • transmitted by the ingestion of eggs
            • Enterobius vermicularis
            • Ascaris lumbricoides
            • Trichuris trichiura
            • Toxocara canis 
          • transmitted by the invasion of lavae through the skin
            • Strongyloides stercoralis
            • Ancylostoma braziliense/caninum
            • Necator americanus 
          • transmitted by the ingestion of larvae
            • Trichinella spiralis 
          • transmitted by arthropods
            • Wucheria bancrofti
            • Loa loa
            • Onchocerca volvulus
            • Dracunculus medinensis 

 

Transmitted by the ingestion of eggs ("EATT")
Enterobius vermicularis
  • Introduction
    • also known as pinworms
    • transmitted by ingestion of eggs
  • Diseases
    • perianal pruritis
      • intestinal infection with anal itching
      • scotch tape on anal area to diagnose presence of microscopic eggs
      • initial infection is from contaminated food
      • hand-to-mouth after scratching perpetuates infection
      • most common helminth parasite in U.S.
  • Treatment 
    • -bendazoles
    • pyrantel pamoate

 

Ascaris lumbricoides
  • Introduction
    • also known as giant roundworm
    • most common helminth parasite worldwide
      • in U.S., seen in mountainous south
    • transmitted by ingestion of eggs
  • Diseases
    • ascariasis 
      • GI and pulmonary symptoms
      • lifecycle involves intestine → lungs → intestine
        • eggs ingested
        • larvae penetrate intestinal wall  
        • hematogenous dissemination to lungs
        • growth in alveoli
        • coughed up
        • swallowed
        • mature in intestine
        • excreted in feces
      • eggs visible in feces 
  • Treatment
    • -bendazoles
    • pyrantel pamoate

 

Trichuris trichiura
  • Introduction
    • also known as whipworm
    • slow lifecycle
    • transmitted by ingestion of eggs
  • Diseases
    • intestinal prolapse
    • abdominal pain and diarrhea
  • Treatment
    • -bendazoles

 

 

Toxocara canis
  • Introduction
    • also known as dog roundworm
    • transmitted by ingestion of eggs
  • Diseases
    • visceral larva migrans
      • larvae wander through body causing inflammation
    • granulomas
      • leads to blindness if in retina
  • Treatment
    • albendazole
    • mebendazole

 

 

 

Transmitted by the invasion of larvae through the skin ("SANd")
Strongyloides stercoralis
  • Introduction
    • also known as threadworm
    • larvae in soil penetrate skin 
    • lifecycle involves intestine → lungs → intestine (see above)
    • eggs are not present in stool
    • autoinfection perpetuates indefinitely if not treated
  • Diseases
    • GI
      • vomiting, diarrhea, malabsorption, anemia, ulcers, bloody stools
    • pneumonitis
  • Treatment
    • -bendazoles
    • ivermectin

 

Ancylostoma braziliense/caninum
  • Introduction
    • also known as dog and cat hookworm
  • Diseases
    • cutaneous larva migrans
      • also known as "creeping eruption"
      • raised, red, itchy rash that moves as larvae move
  • Treatment
    • -bendazoles

 

 

 

Necator americanus
  • Introduction
    • also known as new world hookworm
    • larvae enter through intact skin of bare feet
    • lifecycle involves intestine → lungs → intestine
  • Diseases
    • anemia 
      • sucks blood from intestinal walls
    • pneumonitis
      • if migration to lungs
  • Treatment
    • -bendazoles
    • pyrantel pamoate

 

 

Transmitted by the ingestion of larvae
Trichinella spiralis
  • Introduction
    • only helminth tested on Step 1 transmitted by ingestion of larvae
  • Diseases
    • trichinosis
      • larvae encyst in muscle causing inflammation and pain
      • periorbital edema
      • larvae ingested from undercooked meat
        • usually pork
  • Treatment
    • -bendazoles

 

 

Transmitted by arthropods
Wucheria bancrofti
  • Introduction
    • transmitted by female mosquito bite
      • symptoms develop 9-12 months after bite
  • Diseases
    • elephantiasis
      • blockage of lymphatic vessels leads to swelling disfiguration of extremities
  • Treatment
    • diethylcarbamazine
Loa loa
  • Introduction
    • also known as African eye worm
    • transmitted by Chrysops (deer fly), horse fly, and mango fly bites
  • Diseases
    • worms in conjunctiva
    • Calabar swelling
      • painful, subcutaneous swelling of skin
  • Treatment
    • diethylcarbamazine
Onchocerca volvulus
  • Introduction
    • transmitted by female blackfly bite
  • Diseases 
    • river blindness
      • microfilariae (larvae) migrate to eyes causing blindness
      • thickened, hyperpigmented skin ("lizard skin")
    • allergic reaction to microfilariae is possible
  • Treatment 
    • ivermectin ("to cure rIVER blindness")

 

 

Dracunculus medinensis
  • Introduction
    • also known as guinea worm 
    • transmitted through drinking water infected with copepods (small crustaceans)
    • eradicated except in Africa
  • Diseases
    • skin inflammation and ulceration
    • worm eruption from skin
      • female pokes through host to expose uterus in order to transmit eggs
  • Treatment
    • niridazole
    • slow worm removal with stick
 

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