Enterobiasis

Introduction

Enterobiasis is caused by a small intestinal parasite called Enterobius vermicularis 

-it is the most common intestinal nematode in the United States with highest prevalence in school-aged children 

-Transmission is by the fecal-oral route 

-Gravid female worms migrate nocturnally from the cecum to the perianal region to deposit large numbers of eggs 

Symptoms & Signs 

-Most individuals with pinworm infection are asymptomatic

-The most common symptom is perianal pruritis, which is most severe at night 

-Enuresis, restlessness, insomnia, perianal scratching, cellulitis, impetigo 

Diagnosis 

-Diagnosis can be made by “Scotch Tape” technique: Apply adhesive cellulose tape to the anal region and examine under thee microscope for ova 

-Eggs are football shaped with a thin outer shell

Treatment 

-The treatment of choice is albendazole

-Other effective agents: Mebendazole, Pyrantel pamoate 

-All family members may need treatment


Strongyloidiasis

Introduction

Strongyloidiasis is caused by S. stercoralis, a Nematode parasite

-Humans are the only hosts: It’s life cycle differs from that of most other helminths in that its entire life cycle may be completed within the human host 

-it is acquired by direct contact of skin with larvae or by ingestion of food contaminated with larvae 

-Life cycle: Filariform larvae (infectious) penetrate the skin, enter the blood, migrate to the lungs, move into alveoli, ascend up the trachea, swallowed, enter the colon, produce eggs which form rhabditiform larvae(non-infectious), which are passed in the feces

Autoinfection: Rhabditiform larvae can transform into filariform larvae in human host resulting in seeding of the perianal area with parasites; immunosuppression enhances risk of autoinfection  

-Of the common helminths, only  strongyloides may persist in the human host indefinitely

Symptoms & Signs 

Skin: A serpiginous urticarial rash in response to the migrating larvae; Generalized petechiae and reticular purpura of thee arms, legs, and abdomen with a characteristic thumbprint periumbilical distribution

Thumbprint sign: A unique pattern of periumbilical purpura resembling multiple thumbprints 

Larval currens: External autoinfection producing raised, red, serpiginous lesions over the buttocks, abdomen and back 

Pulmonary and intestinal manifestations can be like hookworm and Ascaris infections

Lungs: Cough, fever, eosinophilia

GI: Peptic-ulcer like pain, nausea, vomiting, diarrhea, constipation, malabsorption, weight loss

Hyperinfection: The most severe complication of Strongyloidiasis is hyperinfection

Immunodeficiency due to HIV,  human T-lymphotropic virus-1 (HTLV-1), has a stronger association with Strongyloides hyperinfection

Lung:  the most common extraintestinal manifestation of hyperinfection syndrome is pulmonary disease; Cough, wheezing, dyspnea, hemoptysis 

GI: Abdominal pain, diarrhea, ileus 

Other organs: liver, urinary tract, brain 

Diagnosis 

Larvae: Diagnosis depends on finding larvae, rather than eggs, in the stool

Serology: Serology via ELISA 

Labs: Eosinophilia 

Treatment 

Effective agents: Ivermectin (Drug of choice), Albendazole