What is the recommended treatment for intestinal parasites?

Treatment of Intestinal Parasites

Albendazole 400 mg as a single oral dose is the first-line treatment for most common intestinal helminths (roundworm, hookworm, pinworm), while metronidazole or tinidazole are the drugs of choice for protozoal infections like giardiasis and amebiasis. 1

Helminthic (Worm) Infections

Roundworm (Ascaris lumbricoides)

• Albendazole 400 mg as a single oral dose is the recommended first-line treatment 2, 1
• Alternative options include mebendazole 500 mg single dose or ivermectin 200 μg/kg single dose 2
• Diagnosis is confirmed by concentrated stool microscopy or direct visualization of adult worms in stool 2
• Complications requiring surgical intervention include intestinal or biliary obstruction, particularly in children 2

Hookworm (Ancylostoma duodenale/Necator americanus)

• Albendazole 400 mg daily for 3 days is recommended by the CDC 1
• Alternative single-dose regimen: albendazole 400 mg as a single dose 3
• For severe hookworm disease with anemia, add prednisolone 40-60 mg once daily 1
• Iron supplementation and blood transfusion may be necessary for significant anemia 4

Pinworm (Enterobius vermicularis)

• Albendazole 400 mg as a single dose 3, 1
• Alternative: mebendazole 100 mg as a single dose 3
• Treat all household contacts simultaneously due to high contagiousness 1
• Repeat treatment in 2 weeks to eliminate newly hatched worms 3
• Diagnosis is made by the "sellotape test" applied to perianal skin 3

Whipworm (Trichuris trichiura)

• Mebendazole 100 mg twice daily PLUS ivermectin 200 μg/kg once daily for 3 days 1
• This combination therapy is recommended by the Infectious Diseases Society of America 1

Threadworm/Strongyloides

• Albendazole 400 mg twice daily for 21 days with monitoring of liver function and complete blood count 1
• Critical precaution: Screen for Loa loa infection before giving ivermectin in patients from Central/West Africa to prevent severe encephalopathy 1
• Before any immunosuppressive therapy, give systematic ivermectin to patients who have stayed in tropical areas, even briefly and even decades ago, to prevent disseminated strongyloidiasis which can be lethal 5

Tapeworm (Taenia species)

• Praziquantel 10-20 mg/kg as a single dose for most Taenia species 3
• For dwarf tapeworm (Hymenolepis nana): praziquantel 25 mg/kg as a single dose (higher dose required) 3
• If Taenia solium is identified or species unknown, consider cysticercosis serology as neurocysticercosis may coexist and requires steroids plus albendazole 3

Trichinellosis (Trichinella species)

• Albendazole 400 mg once daily for 3 days for mild disease 3
• For severe disease with myocarditis or respiratory failure, treatment duration may need extension 3
• Diagnosis by serology (3-5 weeks to seroconversion) or muscle biopsy 3

Protozoal Infections

Giardiasis (Giardia lamblia)

• Metronidazole 250-750 mg three times daily for 7-10 days 3
• Alternative: tinidazole 2 g as a single oral dose (cure rates 80-100%) 6, 7
• Alternative: nitazoxanide (approved for children): 100 mg twice daily for ages 1-3 years, 200 mg twice daily for ages 4-11 years 3
• Diagnosis by stool microscopy with direct fluorescent antibody testing 7
• Albendazole also has good efficacy against giardiasis 5

Amebiasis (Entamoeba histolytica)

For intestinal amebiasis:

• Metronidazole 750 mg three times daily for 5-10 days 3
• PLUS a luminal agent: either diiodohydroxyquin 650 mg three times daily for 20 days OR paromomycin 500 mg three times daily for 7 days 3
• The combination attacks both tissue and luminal life-cycle stages 4

For amebic liver abscess:

• Metronidazole 750 mg three times daily for 5-10 days 3
• Aspiration or drainage of pus when clinically necessary 8
• Chloroquine may be added for liver abscess 4
• Tinidazole 2 g daily for 2-5 days is an alternative with cure rates 81-100% 6

Cryptosporidiosis

• Effective HAART (highly active antiretroviral therapy) is the recommended treatment for HIV-infected patients, as immune reconstitution frequently clears the infection 3
• Nitazoxanide for persistent symptoms >2 weeks: 100 mg twice daily for ages 1-3 years, 200 mg twice daily for ages 4-11 years 3, 7
• Nitazoxanide has 88% clinical response in HIV-uninfected children but is less effective in HIV-infected children with low CD4 counts 3
• Paromomycin 500 mg three times daily for 14-28 days may be considered for severe disease, though evidence is limited 3
• Supportive care with hydration, electrolyte correction, and nutritional supplementation is essential 3

Isospora belli

• TMP-SMX 160/800 mg four times daily for 10 days 3
• For AIDS patients: follow with TMP-SMX three times weekly indefinitely as maintenance therapy 3

Cyclospora cayetanensis

• TMP-SMX 160/800 mg twice daily for 7 days 3
• For AIDS patients: TMP-SMX three times weekly indefinitely after initial treatment 3
• Diagnosis by microscopy or PCR assays 7

Microsporidiosis

• Albendazole 400 mg twice daily for 3 weeks 3, 1
• HAART including a protease inhibitor is warranted for AIDS patients 3
• Note: Albendazole is effective for Encephalitozoon species but NOT for Enterocytozoon bieneusi 3

Empirical Treatment Strategy

For patients from endemic areas with high pretest probability but negative stool tests:

• Albendazole 400 mg PLUS ivermectin 200 μg/kg as a single combined dose 1
• This approach is cost-effective and saves lives compared to screening alone 9
• Presumptive treatment of all immigrants at risk prevents 33 deaths and 374 hospitalizations per year while saving $4.2 million annually 9

Critical Precautions and Monitoring

Before Immunosuppression

• Systematically treat with ivermectin any patient who has stayed in tropical areas (even briefly, even decades ago) before starting immunosuppressive therapy to prevent lethal disseminated strongyloidiasis 5

Loa loa Screening

• Screen for Loa loa before giving ivermectin in patients from Central/West Africa to prevent severe encephalopathy 1

Special Populations

• Seek specialist advice for immunocompromised patients, children aged 12-24 months, and severe disease requiring intensive care 1
• Monitor liver function and complete blood count during prolonged albendazole therapy 1

Shigellosis (Bacterial Dysentery)

While not a parasite, shigellosis commonly presents with bloody diarrhea and must be differentiated:

• First-line: TMP-SMX 160/800 mg twice daily for 5 days OR fluoroquinolone (ciprofloxacin 500 mg twice daily for 3 days) 3
• For resistant strains: nalidixic acid 55 mg/kg/day in four divided doses for 5 days 3
• If no clinical response after 2 days, change antibiotic; if no improvement after another 2 days, refer for stool microscopy to rule out amebiasis 3

Prevention Measures

• Hand hygiene with soap before eating and after defecation 1
• Wear shoes in endemic areas to prevent hookworm 1, 4
• Treat household contacts for highly contagious infections like pinworm 1
• Consume bottled water and peeled foods in endemic areas 4
• Proper sewage treatment and sanitation 4