What are the potential causative agents and treatment options for a patient presenting with acute gastroenteritis and eosinophilia?

Causative Agents of Acute Gastroenteritis with Eosinophilia

For acute gastroenteritis presenting with eosinophilia, prioritize evaluation for helminthic parasites—particularly hookworm, Ascaris, Strongyloides, and Schistosoma species—as these are the most common causative agents, followed by consideration of eosinophilic gastroenteritis if parasitic workup is negative. 1

Primary Parasitic Causes

Helminthic Infections (Most Common)

Hookworm (Ancylostoma duodenale/Necator americanus)

• Presents with nausea, vomiting, diarrhea, and abdominal pain during the migratory phase 1
• May cause Loeffler's syndrome with wheeze and dry cough 1
• Transmitted via skin penetration from contaminated soil 1
• Diagnosed by concentrated stool microscopy 1
• Treat with albendazole 400 mg single dose 1

Ascaris lumbricoides (Roundworm)

• Causes diarrhea and can lead to intestinal or biliary obstruction 1
• Associated with Loeffler's syndrome and urticarial rash 1
• Diagnosed by concentrated stool microscopy 1
• Treat with albendazole 400 mg single dose 1

Strongyloides stercoralis

• Produces non-inflammatory diarrhea often with marked eosinophilia 1
• Critical to diagnose before immunosuppression due to hyperinfection risk 1
• Can persist indefinitely and cause symptoms years after acquisition 1
• Diagnosed by serology (preferred) or repeated stool examinations 1
• Treat with ivermectin 200 μg/kg daily for 2 days 2

Schistosomiasis (S. mansoni, S. haematobium, S. japonicum)

• Acute schistosomiasis (Katayama syndrome) presents with abdominal pain, diarrhea, fever, and marked eosinophilia 1
• Occurs 3-5 months after freshwater exposure 1
• Diagnosed by serology; stool/urine microscopy often negative in acute phase 1
• Treat with praziquantel 40 mg/kg twice daily for 1 day (or 5 days for CNS involvement) 2, 1

Other Parasitic Causes

Trichinellosis (Trichinella species)

• Presents with upper abdominal pain, fever, vomiting, and diarrhea followed by severe myalgia 1
• Transmitted via undercooked pork 1
• Marked eosinophilia >3 × 10⁹/L with elevated creatinine kinase 1
• Treat with albendazole 400 mg daily for 3 days (mild disease) 1

Enterobius vermicularis (Pinworm)

• Can occasionally cause colitis with eosinophilia 1
• Presents with weight loss, irritability, diarrhea, and abdominal pain 1
• Treat with albendazole 400 mg twice daily for 21 days 1

Cystoisospora belli (Cystoisosporiasis)

• Causes sudden onset watery diarrhea, abdominal cramps, nausea, and occasional fever 1
• Self-limiting in immunocompetent patients within 5 days 1
• For prolonged symptoms, treat with trimethoprim-sulfamethoxazole 960 mg twice daily for 7 days 1

Non-Parasitic Causes

Eosinophilic Gastroenteritis (Primary EGE)

• Diagnosis of exclusion after ruling out parasitic infections 3, 4
• Characterized by eosinophilic infiltration >20 eosinophils per high-power field in gastric/duodenal biopsies 3
• Strongly associated with food allergies; 70% have concomitant atopic diseases or family history of allergies 4
• Peripheral eosinophilia present in approximately two-thirds of patients 4
• Treat with corticosteroids as mainstay therapy; elimination diets also effective 3, 4

Other Rare Causes

• Dientamoeba fragilis and Toxoplasma gondii (protozoa) may rarely present with eosinophilia 1
• Visceral larva migrans presents with abdominal pain and hepatosplenomegaly 1
• Paragonimiasis commonly presents with abdominal pain and diarrhea before respiratory symptoms develop 1

Diagnostic Algorithm

Initial Workup

• Obtain complete blood count to document eosinophilia 1
• Perform concentrated stool microscopy for ova, cysts, and parasites (3 samples increase sensitivity) 1
• Consider faecal PCR for specific parasites 1
• Obtain detailed travel history to endemic regions 1

Serological Testing

• Strongyloides serology for patients from endemic areas, regardless of eosinophil count 1
• Schistosomiasis serology if freshwater exposure in Africa or endemic regions 1
• Consider empiric treatment if high clinical suspicion despite negative initial tests 1

Endoscopic Evaluation

• Indicated if stool studies negative and symptoms persist 3
• Obtain multiple biopsies from stomach and duodenum 3
• Look for >20 eosinophils per high-power field to diagnose eosinophilic gastroenteritis 3

Treatment Approach

For Asymptomatic Eosinophilia with Travel History

• Albendazole 400 mg single dose plus ivermectin 200 μg/kg single dose 2

For Confirmed Parasitic Infections

• Treat according to specific organism identified (see individual treatments above) 1, 2

For Eosinophilic Gastroenteritis (After Excluding Parasites)

• Corticosteroids remain most effective: prednisone 40-60 mg daily with gradual taper 3, 4, 5
• Consider elimination diets or elemental formulas, particularly in children 4, 6
• Alternative agents include mast cell stabilizers, leukotriene antagonists, and immunomodulators for refractory cases 3, 6

Critical Pitfalls to Avoid

• Never start corticosteroids before excluding Strongyloides, as this can precipitate fatal hyperinfection syndrome 1
• Stool microscopy has low sensitivity for Strongyloides; serology is preferred 1
• Eosinophilia may be absent in some helminth infections, so testing for eosinophilia alone is inadequate screening 2
• Schistosomiasis serology and stool/urine microscopy are often negative in acute Katayama syndrome 1
• Eosinophilic gastroenteritis has patchy distribution; multiple biopsies are essential 4
• Peripheral eosinophilia is present in only two-thirds of eosinophilic gastroenteritis cases 4