🦠 Parasitic Infections

by Didactic Med

Evidence-Based Guidelines for the 15 Most Common Parasites in the USA

CDC Guidelines 2025

📊 Overview of Parasitic Infections in the USA

100M+

Americans affected by parasitic infections

60M+

Infected with Toxoplasma gondii

14%

US population exposed to Toxocara

3.7M

Affected by Trichomoniasis annually

Most Common Parasitic Infections

Click on any parasite card for detailed information:

🔬 Diagnostic Approach

General Diagnostic Methods

  • Stool O&P Examination: Gold standard for intestinal parasites (3 samples, 24h apart)
  • Serologic Testing: For Toxoplasma, Strongyloides, Schistosoma antibodies
  • Blood Smear: For Babesia, Malaria, and other blood parasites
  • PCR Testing: Molecular detection for many protozoan infections
  • Antigen Detection: For Giardia, Cryptosporidium (rapid tests available)
  • Imaging Studies: CT/MRI for neurocysticercosis, hepatic lesions
  • Eosinophilia Workup: CBC with differential for parasitic screening

When to Suspect Parasitic Infection

  • • Unexplained eosinophilia (>500 cells/μL)
  • • Travel history to endemic areas
  • • Persistent GI symptoms despite treatment
  • • Immunocompromised patients with unusual symptoms
  • • New-onset seizures with cystic brain lesions
  • • Chronic fatigue with unclear etiology
  • • Unexplained anemia or vitamin deficiencies

CDC Diagnostic Resources

DPDx Laboratory Assistance:

Email: dpdx@cdc.gov

Parasitic Diseases Hotline:

Phone: 404-718-4745

Email: parasites@cdc.gov

Available 24/7 for life-threatening cases

🦠 All Parasites - Detailed Information

Browse comprehensive information about all parasites. Click on any card from the Overview section to see detailed information.

💊 Treatment Guidelines

General Treatment Principles

  • • Always confirm diagnosis before treatment when possible
  • • Consider empiric treatment in high-risk populations
  • • Monitor for drug interactions and contraindications
  • • Follow up with repeat testing to confirm cure
  • • Treat household contacts when indicated
  • • Consider resistance patterns in treatment failure

Special Populations

Pregnancy: Avoid albendazole, praziquantel in 1st trimester

Children: Adjust doses by weight; some drugs not approved <2 years

Immunocompromised: May need prolonged or intensive treatment

CNS involvement: Requires specialist consultation

Elderly: Consider renal/hepatic function adjustments

Treatment Monitoring

  • • Repeat stool exams 2-4 weeks post-treatment
  • • Monitor eosinophil count normalization
  • • Serologic follow-up for tissue parasites
  • • Clinical symptom resolution assessment

🛡️ Prevention Strategies

Food & Water Safety

  • • Wash hands thoroughly before eating and after toilet use
  • • Cook meat to safe temperatures (165°F for poultry, 160°F for ground meat)
  • • Wash fruits and vegetables thoroughly
  • • Drink only purified water in endemic areas
  • • Avoid raw or undercooked seafood and meat
  • • Freeze fish for sushi at -4°F for 7 days

Environmental Precautions

  • • Wear shoes when walking on soil
  • • Use insect repellent in endemic areas
  • • Regular deworming of pets
  • • Proper disposal of human and animal feces
  • • Avoid swimming in contaminated freshwater
  • • Cover sandboxes when not in use

Travel Precautions

  • • Pre-travel consultation for endemic area visitors
  • • Prophylactic treatment when indicated
  • • Post-travel screening for high-risk exposures
  • • Avoid contact with triatomine bugs (Chagas vectors)
  • • Use bed nets in endemic areas

📚 Resources & References

CDC Resources

Key Guidelines

  • • IDSA Guidelines for Parasitic Infections
  • • WHO Guidelines for Mass Drug Administration
  • • American Family Physician - Neglected Parasitic Infections Update
  • • Clinical Microbiology Reviews - Parasitic Disease Updates
  • • Red Book - AAP Guidelines for Pediatric Infections

Emergency Consultations

CDC Emergency Operations Center

Phone: 770-488-7100 (ask for Parasitic Diseases on-call)

Available 24/7 for urgent clinical consultations


CDC Drug Service

Phone: 404-639-3670

For rare antiparasitic medications

MEDICATIONS

💊 Antiparasitic Medications

Albendazole
Adult: 400mg PO once or BID x 3-7 days
Pediatric: 200mg (12-23 months), 400mg (≥24 months)
Indications: Ascariasis, Hookworm, Whipworm, Strongyloides (alternative)
Ivermectin
200 mcg/kg PO single dose
Indications: Strongyloidiasis (first-line), Ascariasis, Scabies
Praziquantel
40-60 mg/kg PO in 2-3 divided doses
Indications: Schistosomiasis, Cysticercosis, Tapeworms
Metronidazole
500-750mg PO TID x 7-10 days
Indications: Giardiasis, Trichomoniasis, Amebiasis
Nitazoxanide
Adult: 500mg PO BID x 3 days
Pediatric: Age-based dosing
Indications: Cryptosporidiosis, Giardiasis
Pyrimethamine + Sulfadiazine
Pyrimethamine 25-100mg + Sulfadiazine 1-1.5g QID
Indications: Toxoplasmosis (with folinic acid)
TMP-SMX
160/800mg (DS) PO BID x 7-10 days
Indications: Cyclospora, Isospora, PCP prophylaxis
Atovaquone
750mg PO BID x 21 days
Indications: Babesiosis (with azithromycin), PCP
Benznidazole
5-7 mg/kg/day PO in 2 doses x 60 days
Indications: Chagas disease (CDC Drug Service)
Paromomycin
25-35 mg/kg/day PO in 3 doses x 7 days
Indications: Amebiasis, Cryptosporidiosis (HIV)
⚠️ Important Notes:
  • • Some medications require CDC Drug Service
  • • Always check for drug interactions
  • • Adjust doses for renal/hepatic impairment
  • • Monitor for adverse effects
  • • Pregnancy category varies by drug