What is the treatment for parasitic infections?

Treatment of Parasitic Infections

For intestinal parasitic infections, treatment depends on the specific parasite identified, with albendazole 400 mg as a single oral dose being the first-line therapy for most common helminthic infections (roundworms, hookworms), while protozoal infections require targeted agents like nitazoxanide for Giardia and Cryptosporidium. 1, 2

Helminthic (Worm) Infections

Common Intestinal Helminths

Hookworm (Ancylostoma duodenale, Necator americanus):

• Albendazole 400 mg orally as a single dose, repeated in 2 weeks 3
• Alternative: Mebendazole 500 mg single dose or 100 mg twice daily for 3 days 1, 3
• Alternative: Ivermectin 200 μg/kg single dose (particularly when benzimidazoles unavailable or in areas with documented mebendazole resistance) 1, 3
• Critical consideration: Iron supplementation is essential in heavy infections due to blood loss from intestinal attachment 3

Ascariasis (Ascaris lumbricoides - roundworm):

• Albendazole 400 mg single dose OR mebendazole 500 mg single dose OR ivermectin 200 μg/kg single dose 1

Pinworm (Enterobius vermicularis):

• Albendazole 400 mg single dose OR mebendazole 100 mg single dose 2
• Diagnosis via "sellotape test" examining perianal skin for ova 1

Whipworm (Trichuris trichiura):

• Mebendazole 100 mg twice daily PLUS ivermectin 200 μg/kg once daily for 3 days 2
• Pitfall to avoid: Single-dose mebendazole is inadequate; combination therapy with ivermectin is required for adequate cure rates 2

Strongyloidiasis (Strongyloides stercoralis):

• Ivermectin 200 μg/kg orally is the treatment of choice 4
• Critical warning: This infection can cause fatal hyperinfection syndrome in immunocompromised patients; urgent diagnosis and treatment are essential 1, 5
• For suspected hyperinfection: urgent stool and sputum microscopy to look for larvae 1

Tapeworm Infections

Taenia saginata (beef tapeworm):

• Praziquantel 10 mg/kg single dose 1, 2
• Alternative: Niclosamide 2 g single dose 1

Taenia solium (pork tapeworm):

• Niclosamide 2 g single dose (kills adult worms only) 1, 2
• Critical pitfall: Praziquantel should NOT be used unless concomitant neurocysticercosis has been excluded 1

Hymenolepis nana (dwarf tapeworm):

• Praziquantel 25 mg/kg single dose 1, 2
• Alternative: Niclosamide 2 g once daily for 7 days 1

Echinococcus (hydatid disease):

• Albendazole 400 mg twice daily, duration determined by cyst type 1
• Add praziquantel 20 mg/kg twice daily for 2 weeks pre- and post-aspiration or surgery 1
• PAIR (puncture, aspiration, injection, re-aspiration) plus drug therapy for simple liver cysts >5 cm 1

Schistosomiasis

Schistosoma species:

• Praziquantel 40 mg/kg single dose for S. mansoni, S. intercalatum, S. guineensis 1
• Praziquantel 60 mg/kg in two divided doses for S. japonicum and S. mekongi 1
• Important: Where diagnosis is based on serology alone and schistosomiasis from Asia-Pacific region is suspected, treat with 60 mg/kg praziquantel in two divided doses 1

Protozoal Infections

Giardia lamblia:

• Nitazoxanide: Children 1-3 years: 100 mg twice daily for 3 days; Children 4-11 years: 200 mg twice daily for 3 days 2
• Clinical response of 88% in HIV-uninfected children 1, 2

Cryptosporidium:

• Nitazoxanide at age-appropriate dosing for 3 days 1, 2
• Critical: Supportive care with hydration and correction of electrolyte abnormalities is essential 1, 2
• Important caveat: In HIV-infected children with CD4 <50/µL, nitazoxanide may be no more effective than placebo 1
• Effective HAART is the recommended treatment for HIV-infected patients, as immune reconstitution frequently results in clearance 1

Entamoeba histolytica (amebiasis):

• Requires specific anti-amebic therapy (metronidazole followed by a luminal agent) 6

Isospora belli:

• Co-trimoxazole is effective 6

Cyclospora:

• Co-trimoxazole is highly effective 6

Microsporidium:

• Albendazole (variable response depending on species) 6

Leishmaniasis

Visceral leishmaniasis:

• Liposomal amphotericin B (L-AmB) is FDA-approved for treatment 1
• Oral miltefosine is FDA-approved for VL caused by particular species 1

Cutaneous leishmaniasis:

• Treatment must be individualized based on parasite species, lesion characteristics, and host factors 1
• Options include systemic antimonials, L-AmB, miltefosine, or local therapies 1
• Consultation with a leishmaniasis expert is strongly recommended 1

Babesiosis

Babesia species:

• Atovaquone 750 mg orally every 12 hours PLUS azithromycin 500-1000 mg on day 1, then 250 mg once daily for 7-10 days 1
• Alternative (for severe disease): Clindamycin 300-600 mg every 6 hours IV PLUS quinine 650 mg every 6-8 hours orally 1
• Severe disease criteria: High-grade parasitemia (≥10%), significant hemolysis, or renal/hepatic/pulmonary compromise requires clindamycin-quinine and consideration of exchange transfusion 1

Critical Management Principles

Diagnostic approach:

• Submit at least 3 stool samples for microscopy when parasites shed intermittently 1, 2
• Concentrated stool microscopy or fecal PCR for most helminthic infections 1
• Serology for schistosomiasis, strongyloidiasis, and tissue parasites 1

Follow-up:

• Repeat stool examination 2-4 weeks after treatment for persistent symptoms 2, 7
• Small numbers of hookworm or roundworm eggs may be passed for up to 7 days post-treatment despite worm elimination 7

Prevention of reinfection:

• Hand and fingernail hygiene with soap 2
• Wearing shoes in endemic areas 3
• Screen and treat household contacts in endemic settings 3
• Adequate sanitation and safe water access 8, 9

Special populations:

• Treat all confirmed infections in children, even if asymptomatic, to prevent transmission and complications 2
• Pregnancy warning: None of the helminthic drugs are safe for use in pregnant women 5
• Immunocompromised patients may require higher doses (e.g., azithromycin 600-1000 mg daily for babesiosis) 1

Common pitfalls to avoid:

• Do not use antimotility agents in young children with protozoal diarrhea 1, 2
• Do not rely on single stool sample for diagnosis 2
• Do not overlook neurocysticercosis screening when Taenia solium is identified 2
• For prolonged exposure in endemic areas with negative stool tests, treat empirically with albendazole 400 mg plus ivermectin 200 μg/kg due to high false-negative rates 3