Treatment of Human Parasitic Infections
The treatment of human parasitic infections requires specific antiparasitic medications tailored to the type of parasite, with combination therapy often necessary to effectively eliminate both tissue and intestinal forms of the parasites. 1, 2
General Approach to Treatment
- All symptomatic parasitic infections should be treated with appropriate antiparasitic therapy to prevent complications 1
- Diagnosis should include identification of the specific parasite through microscopy, PCR, or other appropriate testing before initiating treatment 2
- Treatment regimens must be selected based on the specific parasite identified and the severity of infection 1
Treatment by Parasite Type
Protozoan Infections
Intestinal Amoebiasis (Entamoeba histolytica)
- First-line treatment: Metronidazole 750 mg orally three times daily for 5-10 days 2
- Must be followed by a luminal agent to eliminate intestinal cysts:
- Paromomycin 500 mg three times daily for 7 days, OR
- Diloxanide furoate 500 mg three times daily for 10 days 2
- Failure to provide a luminal agent after metronidazole therapy is a common cause of relapse 2
Babesiosis
- For mild to moderate disease: Atovaquone 750 mg orally every 12 hours plus azithromycin 500-1000 mg on day 1, then 250 mg daily for 7-10 days 1
- For severe disease: Clindamycin 300-600 mg IV every 6 hours (or 600 mg orally every 8 hours) plus quinine 650 mg orally every 6-8 hours 1
- Exchange transfusion is indicated for patients with high-grade parasitemia (>10%), significant hemolysis, or organ dysfunction 1
Giardiasis
- Metronidazole is effective for treating symptomatic Giardia lamblia infections 3
Helminth Infections
Strongyloidiasis
- Ivermectin is indicated for treatment of intestinal strongyloidiasis 4
- Hyperinfection syndrome can occur in immunocompromised patients and requires urgent treatment 1
- For disseminated strongyloidiasis, parenteral ivermectin may be life-saving 1
Intestinal Nematodes (Roundworms)
- Albendazole 400 mg as a single dose is effective for treating many intestinal nematodes including Ascaris 1, 5
- For Trichuriasis: Mebendazole is the drug of choice 6
- For hookworm disease: Mebendazole is most effective 6
Filariasis
- Diethylcarbamazine (DEC) is used for lymphatic filariasis: 50 mg on day 1, increasing to 200 mg three times daily for 3 weeks 1
- For Loa loa with microfilaremia, corticosteroids should be used with DEC to prevent encephalopathy 1
- For onchocerciasis, ivermectin is preferred; DEC can cause severe reactions 1, 4
Schistosomiasis
- Praziquantel is the most widely available and effective chemotherapy 7
Special Considerations
Severe Infections
- Patients with moderate-to-severe parasitic infections should be monitored closely during therapy to ensure clinical improvement 1
- In severe babesiosis, clinical parameters and parasitemia should be monitored daily or every other day until improvement occurs 1
Immunocompromised Patients
- Higher doses or longer treatment durations may be required for immunocompromised patients 1
- For babesiosis in immunocompromised patients, higher doses of azithromycin (600-1000 mg per day) may be used 1
- Strongyloidiasis in immunocompromised patients requires special attention due to risk of hyperinfection syndrome 1, 8
Common Pitfalls and Caveats
- Asymptomatic individuals with positive serology but negative parasitemia generally should not receive treatment 1
- Failure to provide a luminal agent after tissue treatment for amoebiasis is a common cause of relapse 2
- Misdiagnosis between parasitic and bacterial infections can lead to inappropriate treatment 2
- When treating onchocerciasis, a test dose of DEC should be given to prevent severe Mazzotti reaction 1
- Treatment failures for babesiosis have been reported in patients with splenectomy, HIV infection, or concurrent corticosteroid therapy 1
Prevention
- Avoiding tick-infested areas is the best method for preventing tick-borne parasitic infections like babesiosis 1
- Use of protective clothing and insect repellents containing DEET can provide additional protection 1
- For travelers returning from endemic areas with eosinophilia, empiric treatment with albendazole and ivermectin may be considered 8