The search performed yielded 33 sources: nine guidelines, ten reviews, and 14 textbook excerpts (Fig. 1, Table 1). Among the searched guideline repositories, only the Association of the Scientific Medical Societies in Germany offers specific guidelines on loiasis therapy. Country-level guidelines were identified from Gabon, Germany and the United Kingdom [6,7,8]. Several guidelines from the United States of America are aimed at practitioners worldwide [9,10,11,12].

Flow of literature search

The recommendations date from 2001 to 2024, with no major changes or new treatment options observed. All publications that did not specify whether they applied to endemic populations or to travellers and migrants were considered applying to both. Of the 33 sources examined, five offered recommendations specifically for treatment in endemic areas, while seven focused solely on returning travellers and migrants. 21 sources provided guidance applicable to both populations. Among the medical guidelines, two addressed only endemic populations, and three focused exclusively on returning travellers and migrants, whereas four covered both groups. In terms of reviews, one was implicitly dedicated to treatment in endemic regions [13], three concentrated on the treatment of returning travellers and migrants, and six addressed both demographics. When considering textbook excerpts, two were specific to endemic regions, one was dedicated to travellers and migrants, and eleven covered both populations. While all selected sources provided recommendations for treating L. loa infection, eleven also offered guidelines on prophylactic therapy, and six made recommendations for managing cases of eye migration. Additionally, one source suggested a treatment regimen suitable for mass drug administration [6]. Four sources considered treatment restrictions for pregnant women or children [9, 12, 14, 15].

The evidence-base, quality, and certainty of the recommendations were low and none except two specified the underlying methodology for the guideline development [7, 8]. Most guidelines lacked evidence grading systems for their recommendations. The recommendations were often very concise, omitting microfilaremia thresholds or drug dosage [16]. Only one of the reviews was a systematic review, which focused rather on symptoms than treatment of loiasis [17]. There is no meta-analysis available which systematically analyses treatment for loiasis.

The identified treatment recommendations showed both similarities and contrasts, particularly in dosage recommendations for diethylcarbamazine, commonly used as a primary treatment across different regions. Most sources recommend initiation of treatment with diethylcarbamazine at a low dose and gradually increasing it, to manage patients effectively and avoid adverse reactions [18, 19]. Typically, diethylcarbamazine full-dose regimens for adults with detected microfilaremia range from 300–400 mg daily [18, 20] to 8–10mg/kg daily [8, 21, 22] over 12 [23] up to 28 days [14, 20], often with repetition of treatment cycles advised if necessary. The starting dose ranges from 3–6 mg daily [10, 24] to 1 mg/kg daily [9, 25,26,27,28]. For hypermicrofilaremic patients, the recommended initial dose can be as low as 0.5 mg/kg [22].

In occult loiasis, maintenance doses of diethylcarbamazine range from 400 mg daily [10, 19, 24, 29] to 8–10 mg/kg daily [8, 22] for the same duration as microfilaremic infection. Not all recommendations mention incremental increase of dosing for occult cases, but those who do, recommend initial doses of 50 mg [8, 10, 19, 24, 29] to 6 mg/kg daily [26]. While most sources recommend repetition of the whole treatment cycle in case of persistent infection, another suggestion is treatment for 10 days per month for three to six months, if needed [19]. However, the difficulties in procurement of diethylcarbamazine are also acknowledged [13].

Ivermectin is another frequently recommended treatment, particularly for patients with a microfilarial load below specific thresholds, highlighting its effectiveness in quickly reducing microfilarial counts [10, 12]. Ivermectin dosing is recommended as alternative treatment when diethylcarbamazine cannot be used, with guidelines recommending a dose of 150 µg/kg [10, 14, 21, 24, 29] to 200 µg/kg [6, 13, 30], most-often as a single-dose [1, 7, 10, 13, 14, 20, 21, 24, 26] but up to a period of ten days in daily doses [6]. Repetitive administrations of ivermectin are considered in some guidelines in monthly [10, 14, 24, 29], quarterly [10, 14, 24, 29] or biannual [13] intervals. Differences arise in frequency and context, such as the Gabonese Health Ministry's recommendation of 200 μg/kg daily for ten days in an endemic setting [6].

Albendazole dosing is commonly prescribed from 400 mg daily [8,9,10,11,12, 14, 15, 18, 20, 21, 24,25,26, 28, 29] to 800 mg daily [1, 2, 6, 7, 31] for 10 days [6] up to 28 days [1, 7, 15, 31], especially for higher microfilarial loads or when diethylcarbamazine treatment is not feasible [10, 12, 29]. Dosing can be as low as 200 mg three times weekly [25] for low microfilaremia. 800 mg dosing is recommended in case of failure to clear infection by diethylcarbamazine regimens [15]. Rarely, mebendazole is given as an albendazole alternative [17, 26, 31].

Microfilarial thresholds show notable similarities across guidelines, with 8000 microfilariae per millilitre (mf/ml) commonly acknowledged as a critical point for altering treatment strategies. This threshold often prompts more cautious interventions, such as the use of albendazole or apheresis instead of diethylcarbamazine. The threshold recommended for diethylcarbamazine treatment is typically below 1000 mf/ml [8, 15, 18, 20, 25, 26, 28], with some guidelines allowing up to 2000 mf/ml [1, 7, 10, 14, 24, 29]. However, a considerable number of publications set the safe threshold for diethylcarbamazine at 8000 mf/ml [2, 11, 12, 21, 30,