What helminths cause diarrhea?

Helminths That Cause Diarrhea

The helminths definitively associated with diarrhea are Trichuris trichiura (whipworm), Strongyloides stercoralis (threadworm), Schistosoma species (particularly S. mansoni), Capillaria philippinensis, hookworms (Ancylostoma duodenale and Necator americanus), and Ascaris lumbricoides (roundworm), though the latter primarily causes diarrhea during heavy infections or acute phases. 1, 2

Definite Causes of Diarrhea

Trichuris trichiura (Whipworm)

• Heavy infections cause significant gastrointestinal symptoms including dysentery, diarrhea, and abdominal pain 1
• Can lead to severe colitis with significant blood loss in heavy infestations 3
• Children may develop anemia, rectal prolapse, and impaired growth and cognitive development 1
• The mechanism involves intimate mucosal contact with strong local inflammatory responses 2

Strongyloides stercoralis (Threadworm)

• Presents with nausea, vomiting, diarrhea, and abdominal pain 1
• Particularly dangerous in immunocompromised patients where it can cause hyperinfection syndrome with severe disease 1, 4
• Can be fatal in debilitated and immunosuppressed individuals 3
• Associated with blood hypereosinophilia 5

Schistosoma species

• Acute schistosomiasis (Katayama syndrome) presents with diarrhea, fever, and pronounced eosinophilia, particularly in newly exposed travelers 1
• S. mansoni is particularly associated with diarrheal disease 2
• Chronic infections more common in migrants may present differently than acute infections in travelers 1

Hookworms (Ancylostoma duodenale and Necator americanus)

• Cause nausea, vomiting, diarrhea, and abdominal pain weeks after skin penetration 1
• Heavy infections result in anemia, particularly in young children and pregnant women 1, 3
• In endemic areas, 90% of pregnant mothers may be anemic due to hookworm 3
• Associated with blood hypereosinophilia 5

Occasional or Context-Dependent Causes

Ascaris lumbricoides (Roundworm)

• Generally does NOT cause diarrhea in typical infections 6
• May cause abdominal pain and diarrhea in some cases, particularly heavy infections 1
• Primarily causes intestinal and biliary obstruction rather than diarrhea 1
• Strictly intraluminal worms like Ascaris typically do not interfere with intestinal function enough to cause diarrhea 2

Hymenolepis nana and H. diminuta

• Usually asymptomatic 1
• Heavy infections may present with diarrhea and abdominal pain 1

Capillaria philippinensis

• Definitively associated with diarrheal disease 2
• Has an invasive phase with intimate mucosal contact causing inflammatory responses 2

Key Clinical Distinctions

Invasive vs. Intraluminal Parasites:

• Helminths that invade the intestinal mucosa (Trichuris, Strongyloides, Schistosoma, Capillaria) cause diarrhea through local inflammatory responses and structural alterations 2
• Strictly intraluminal worms (most Ascaris infections, Enterobius, Taenia) generally do not cause sufficient intestinal dysfunction to produce diarrhea 6, 2

Blood Eosinophilia as a Clue:

• Helminthic diseases causing diarrhea are typically associated with blood hypereosinophilia 5
• This distinguishes them from protozoal causes of diarrhea 5

Diagnostic Approach

• Concentrated stool microscopy or fecal PCR is recommended for diagnosis of intestinal helminths 1
• Eosinophilia may be transient during tissue migration phase before stool tests become positive 1
• Travel history is critical: exposure to freshwater (Schistosoma), walking barefoot (hookworm), or consumption of contaminated food/water (various helminths) 1