Roundworms (Nematodes)

Snapshot

A 5-year-old boy is brought to his pediatrician for abnormal scratching behavior. His mom reports that he has been scratching his anus for the past few days, causing some concern among his schoolteachers. His bowel movements and appetite have been normal. On physical exam, there is some erythema and excoriations from scratching around his anus. His pediatrician conducts a scotch tape test and identifies eggs on microscopy. He is given the correct anti-helminthic therapy.

Introduction

Introduction
- helminths are macroscopic parasitic worms
  - tapeworms (cestodes)
  - flukes (trematodes)
  - roundworms (nematodes)
- roundworms (nematodes)
  - organism characteristics
- transmission
  - ingestion of eggs/larvae
    - Enterobius
    - Ascaris
    - Toxocara
    - Trichuris
    - Trichinella
    - Dracunculus
  - invasion of larvae cutaneously
    - Strongyloides
    - Ancylostoma
    - Necator
  - arthropod bites
    - Loa loa
    - Onchocerca volvulus
    - Wuchereria bancrofti
- treatment
  - most are treated with bendazoles
other options include ivermectin or diethylcarbamazine

Roundworms (Nematodes)
Organism	Clinical Presentation	Transmission	Treatment
Transmission by Ingestion of Eggs
Enterobius vermicularis (pinworm)	Anal pruritus, especially in childrenScotch tape testscotch tape to anal area will show eggs on microscopy Most common helminth parasite in the US	Fecal-oralIngestion of eggs	Bendazoles Pyrantel pamoate
Ascaris lumbricoides (giant roundworm)	Biliary obstructionIntestinal obstruction or perforationMay also affect the lungsOval eggs are seen on stool microscopy	Fecal-oralIngestion of eggsMigrates from the nose/mouth to intestines	Bendazoles
Toxocara canis	Visceral larva migransMyocarditis, liver damage, ocular damage (visual impairment and blindness), and brain damage (seizures and coma)Granuloma formation causes damage	Fecal-oralIngestion of eggsMigrates from intestinal wall to blood	Bendazoles
Trichuris trichiura (whipworm)	Microcytic anemiaAbdominal pain and diarrheaCan cause intestinal/rectal prolapse in children	Fecal-oralIngestion of eggs	Bendazoles
Transmission by Ingestion of Larvae
Trichinella spiralis	TrichinosisFever, vomiting, nausea, periorbital edema, and myalgia	Undercooked meatIngestion of larvae (the only nematode transmitted this way)Migrates from blood to striated muscle, causing inflammation	Bendazoles
Transmission by Cutaneous Penetration
Strongyloides stercoralis (threadworm)	Gastrointestinal upsetPneumonitisLoffler syndromeDermatitisRhabditiform larvae, not eggs, seen on stool microscopy	Penetration from soil into the skin	BendazolesIvermectin
Ancylostoma braziliense Necator americanus (hookworm)	Microcytic anemia Cutaneous larva migrans or “creeping eruption” that moves as the larvae moves Pruritic serpiginous rash	Penetration into the skin, often from walking barefoot on the beachNematode sucks blood from the intestinal wall	BendazolesPyrantel pamoate
Transmission by Arthropods (Bite or Ingestion)
Wucheria bancrofti	Lymphatic filariasis or elephantiasis Lymphedema causing disfiguration of extremities	Via female mosquitoesInvades lymph nodes	Diethylcarbamazine
Loa loa (African eye worm)	Calabar swellings in skinWorms in conjunctiva	Via deer flies, horse flies, and mango flies	Diethylcarbamazine
Onchocerca volvulus	Hyperpigmented rash, river blindness, and black skin nodules	Via female blackflies	Ivermectin (Rivermectin)
Dracunculus medinensis (Guinea worm)	Skin inflammation and ulcerationWorm eruption from skinAnaphylactic shock if worm is pulled from skin and breaks, due to release of foreign antigens	Ingestion of water contaminated with infested water fleas	NiridazoleRemoval of worm that has emerged from skin, by a few cms each day using a rod

Useful Links

Information

Socials