Are individuals with Crohn's (Crohn's disease) more susceptible to parasitic infections?

Susceptibility to Parasitic Infections in Crohn's Disease

Patients with Crohn's disease are not inherently more susceptible to parasitic infections due to their disease alone, but become at increased risk primarily when treated with immunosuppressive medications. 1

Risk Factors for Parasitic Infections in IBD Patients

• Immunosuppressive therapy is the main risk factor for opportunistic infections, including parasitic infections, in Crohn's disease patients 1
• Combination immunosuppressive therapy significantly increases infection risk (up to 14.5-fold with two or more immunosuppressive drugs) 1
• Specific risk factors that increase susceptibility to parasitic infections include:
  • Malnutrition 1
  • Older age (particularly >50 years) 1
  • Active disease (each 100-point increase in CDAI associated with 30% increased infection risk) 1
  • Obese BMI 1
  • Comorbidities 1

Specific Parasitic Concerns in Crohn's Disease

Strongyloides stercoralis

• Strongyloides stercoralis is a particular concern for IBD patients on immunosuppression 1
• Patients on systemic steroids are at risk of potentially fatal hyperinfection syndrome 1
• Blood eosinophilia is common but not universal in Strongyloides infection 1
• Strongyloides serology should be checked prior to commencing anti-TNF therapy in patients who have traveled for long periods or lived in endemic areas 1

Travel-Related Parasitic Risk

• IBD patients who have traveled to or lived in endemic areas have increased risk of parasitic infections 1
• Returning travelers with diarrhea should have:
  • Stool examination for bacterial pathogens, ova, and parasites 1
  • Complete blood count to identify eosinophilia 1
  • Serological blood test for strongyloidiasis for long-term travelers returning from endemic countries 1

Management Considerations

• Screening for parasitic infections should be part of the workup for patients with suspected or worsening Crohn's disease 1, 2
• Strongyloides serology and eosinophil count should be checked before starting anti-TNF therapy in at-risk patients 1
• Treatment for Strongyloides is with ivermectin or albendazole 1
• Parasitic infections are found in approximately 12% of patients with ulcerative colitis who reside in endemic areas 1

Hygiene Hypothesis Perspective

• Some research suggests that lack of exposure to helminthic parasites may actually predispose to Crohn's disease development 3, 4
• The hygiene hypothesis proposes that raising children in extremely hygienic environments with less exposure to parasites may negatively affect immune system development 3
• Helminthic parasites may protect against Th1 cell-mediated gastrointestinal inflammations like Crohn's disease 3, 4

Clinical Implications

• Parasitic infections should be considered in the differential diagnosis of IBD flares, especially in patients on immunosuppression 1
• Escalating immunosuppressive therapy without ruling out infections can worsen outcomes 2
• Patients with Crohn's disease traveling to endemic areas should receive pre-travel counseling and post-travel screening 1