What is the treatment for filariasis?

Treatment of Filariasis

Critical Pre-Treatment Screening is Mandatory

Before initiating any treatment for filariasis, you must screen for co-infections with Loa loa and onchocerciasis, as failure to do so can result in fatal encephalopathy or severe neurological complications. 1, 2

Screening Algorithm:

• Obtain daytime blood microscopy (10 am to 2 pm) using 20 ml citrated blood samples to detect Loa loa microfilariae, as they circulate during daylight hours 1, 3
• Perform skin snip microscopy and slit lamp examination to exclude onchocerciasis before using diethylcarbamazine (DEC), as DEC can cause severe reactions including blindness, hypotension, and erythema in co-infected patients 1, 2
• If skin snips and slit lamp are unavailable, administer a test dose of DEC 50 mg to precipitate a mild Mazzotti reaction if onchocerciasis is present 1, 3
• Determine exact microfilarial count if Loa loa is detected, as counts >1000/ml place patients at highest risk of fatal encephalopathy with DEC treatment 1, 3

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Primary Treatment Regimens for Lymphatic Filariasis

First-Line Treatment (After Excluding Co-Infections):

Diethylcarbamazine (DEC) 6 mg/kg divided into 3 doses daily for 14 days PLUS doxycycline 200 mg daily for 6 weeks is the recommended regimen for lymphatic filariasis. 1, 2

This combination addresses both the parasites and their Wolbachia endosymbionts, providing superior efficacy compared to DEC alone. 4

Alternative Regimen (In Onchocerciasis Co-Endemic Areas):

Ivermectin 200 μg/kg single dose PLUS albendazole 400 mg single dose is recommended where DEC is contraindicated due to onchocerciasis co-endemicity. 1, 2, 5

• Ivermectin should be taken with food, as bioavailability increases 2.5 times with high-fat meals 2
• Albendazole should be taken with or after food 2

Triple-Drug Regimen (Emerging Option):

A single dose of ivermectin, diethylcarbamazine, and albendazole (IDA) has shown dramatically superior efficacy for clearing microfilariae compared to two-drug combinations and is well-tolerated in mass drug administration settings. 6

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Treatment for Loiasis (Loa loa) Co-Infection

High Microfilarial Load (>1000/ml):

Start prednisolone (after screening for strongyloidiasis) followed by albendazole 200 mg twice daily for 21 days to reduce microfilarial load before definitive treatment. 1, 3

• Albendazole can be dosed from 400 mg daily up to 800 mg daily for 10-28 days depending on microfilarial burden 3
• Consider apheresis for extremely high loads (>8,000-30,000 mf/ml) as an adjunct 3
• Mandatory specialist consultation with tropical medicine or parasitology is required before treating any confirmed or suspected Loa loa infection 3

Low Microfilarial Load (<1000/ml) or Negative:

DEC escalating regimen: 50 mg single dose on day 1,50 mg three times daily on day 2,100 mg three times daily on day 3,200 mg three times daily on day 4, then continue 200 mg three times daily for 21 days. 3

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Treatment for Onchocerciasis

Doxycycline 200 mg once daily for 6 weeks, starting ivermectin 200 μg/kg monthly for 3 months on day one of doxycycline. 1

• Note that ivermectin has no activity against adult Onchocerca volvulus parasites; it only targets microfilariae 5
• Surgical excision of palpable nodules (nodulectomy) may be considered to eliminate microfilariae-producing adult parasites 5

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Special Populations

Pregnancy:

• Avoid DEC in pregnancy and seek expert consultation 1, 2
• Ivermectin can be used in second and third trimesters with no observed teratogenicity in limited human data 1, 2, 5

Breastfeeding:

• Ivermectin is excreted in very low levels in breast milk and is likely compatible with breastfeeding 1, 2, 5

Pediatrics:

• Children aged 12-24 months should be discussed with an expert before treatment 1, 2
• Children over 24 months can receive standard dosing 1, 2
• Safety and effectiveness in pediatric patients weighing less than 15 kg have not been established 5

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Monitoring Requirements

• Monitor full blood counts and liver function tests every 2 weeks for 3 months, then monthly if within normal range for prolonged courses 1, 2
• Monitor for adverse reactions including fever, lymphadenitis, and lymphangitis during DEC and doxycycline treatment 1, 2
• Repeat blood microscopy at 6 and 12 months after last negative sample to monitor for relapse in loiasis 1, 3
• Follow-up serological testing in 3-6 months may be warranted to ensure complete parasite clearance in lymphatic filariasis 1

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Critical Drug Interactions and Warnings

• Azithromycin significantly increases serum ivermectin concentrations; use caution with co-administration 1, 2
• Post-marketing reports of increased INR have been rarely reported when ivermectin was co-administered with warfarin 5
• Alcohol may worsen side effects 1, 2
• DEC can cause encephalopathy with high mortality in patients with high Loa loa microfilarial loads 1, 3
• Patients with hyperreactive onchodermatitis (sowda) may be more likely to experience severe adverse reactions, especially edema and aggravation of onchodermatitis 5

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Common Pitfalls to Avoid

• Never initiate DEC or ivermectin without first determining microfilarial count in patients with potential Loa loa exposure, as this is the single most important factor in preventing fatal encephalopathy 3
• Never use DEC in patients with onchocerciasis co-infection without proper screening, as it can cause severe Mazzotti reactions including blindness 1, 5
• Recognize that current treatment recommendations for loiasis show significant inconsistencies with low-quality evidence, as only 2 of 33 sources in a 2025 systematic review detailed their guideline development process 7, 1
• When using DEC with microfilaraemia present, prednisolone is usually given alongside to reduce inflammatory reactions 2