Clinical characteristics and treatments of imported loiasis patients with microfilaraemia diagnosed in France, 2000-2022

INTRODUCTION: Loiasis has been associated with increased morbidity and mortality, particularly in cases of high microfilarial density. Treatment depends on initial microfilaraemia (Mf) and relies on ivermectin (IVM), diethylcarbamazine (DEC) or albendazole (ALB), all associated with serious adverse events. Our objective was to describe the clinical characteristics, management and outcomes of patients diagnosed with loiasis and Mf in France. METHODS: We conducted a multicenter retrospective study including patients with loiasis and Mf diagnosed and treated in France between 2000 and 2022, with at least one follow-up evaluation. We collected clinical and biological data, including Mf kinetics, for each treatment episode. RESULTS: A total of 150 patients (181 treatment episodes) were included across 27 centers. Median age was 35 years, and most patients presented symptoms (75.3%). Median Mf was 500 mf/ml; for 74% of episodes, baseline Mf below 2000 mf/ml, while 8% had baseline Mf above 8000 mf/ml. Twelve different treatment schemes were identified, the most common being a single dose of IVM (39%). Adverse events occurred in 12% of episodes, including one fatal event. On last follow-up visit, 9.3% of patients still experienced symptoms, 24.7% exhibited persistent Mf, and 19.3% had persistent blood eosinophilia, patients treated with stand-alone IVM experienced worse outcomes (18%, 72% and 39%, respectively). CONCLUSION: In France, loiasis treatment is inconsistent and frequently relies on inadequate options, including IVM monotherapy, which lacks therapeutic efficacy, and carries safety concerns. Our findings highlight real-world practices and indicates that better training is needed for practitioners treating patients with loiasis.

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Journal
Travel Medicine and Infectious Disease
Published
2026-04-22
DOI
https://doi.org/10.1016/j.tmaid.2026.102982
Primary Topic
Parasitic Diseases Research and Treatment
Type
article
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article

Clinical characteristics and treatments of imported loiasis patients with microfilaraemia diagnosed in France, 2000-2022

M Robert, Christelle Pomarès, Cléa Melenotte, Estelle Cateau et al.
Travel Medicine and Infectious Disease
Parasitic Diseases Research and Treatment
article

Clinical characteristics and treatments of imported loiasis patients with microfilaraemia diagnosed in France, 2000-2022

M Robert, Christelle Pomarès, Cléa Melenotte, Estelle Cateau, Julie Bonhomme, Frédéric Grenouillet, Gilles Gargala, Olivier Bouchaud, Yohann Le Govic, Vincent Dubée, Anne Donnars, Justine Dorchies, Victor Gerber, Charlotte Boullé, Charles Maurille, Damien Dupont, Jordan Leroy, Laura Courtellemont, Frédérick Gay, Charles Declerck, Assia BENELHADJ DJELLOUL, Antoine Specklin, Pierre Danneels, Claire Hoffmann, Alexandre Duvignaud, Coralie L’Ollivier, Benjamin Lefèvre, Simon Kravetz, Hélène Yera, Jean-Pierre Gangneux, Maeva Lefebvre
article en

Abstract

INTRODUCTION: Loiasis has been associated with increased morbidity and mortality, particularly in cases of high microfilarial density. Treatment depends on initial microfilaraemia (Mf) and relies on ivermectin (IVM), diethylcarbamazine (DEC) or albendazole (ALB), all associated with serious adverse events. Our objective was to describe the clinical characteristics, management and outcomes of patients diagnosed with loiasis and Mf in France. METHODS: We conducted a multicenter retrospective study including patients with loiasis and Mf diagnosed and treated in France between 2000 and 2022, with at least one follow-up evaluation. We collected clinical and biological data, including Mf kinetics, for each treatment episode. RESULTS: A total of 150 patients (181 treatment episodes) were included across 27 centers. Median age was 35 years, and most patients presented symptoms (75.3%). Median Mf was 500 mf/ml; for 74% of episodes, baseline Mf below 2000 mf/ml, while 8% had baseline Mf above 8000 mf/ml. Twelve different treatment schemes were identified, the most common being a single dose of IVM (39%). Adverse events occurred in 12% of episodes, including one fatal event. On last follow-up visit, 9.3% of patients still experienced symptoms, 24.7% exhibited persistent Mf, and 19.3% had persistent blood eosinophilia, patients treated with stand-alone IVM experienced worse outcomes (18%, 72% and 39%, respectively). CONCLUSION: In France, loiasis treatment is inconsistent and frequently relies on inadequate options, including IVM monotherapy, which lacks therapeutic efficacy, and carries safety concerns. Our findings highlight real-world practices and indicates that better training is needed for practitioners treating patients with loiasis.

Travel Medicine and Infectious DiseaseVol. 71
Université Claude Bernard Lyon 1 (FR), Centre National de la Recherche Scientifique (FR), Université de Bordeaux (FR), Inserm (FR), Institut Pasteur (FR), Aix-Marseille Université (FR), Centre Hospitalier Universitaire de Grenoble (FR), Centre Hospitalier Universitaire de Lille (FR), Centre Hospitalier Universitaire de Nice (FR), Sorbonne Université (FR), Centre Hospitalier Universitaire de Besançon (FR), Université Sorbonne Paris Nord (FR), Centre de Recherche en Neurosciences de Lyon (FR), Centre Hospitalier Universitaire Amiens-Picardie (FR), Assistance Publique – Hôpitaux de Paris (FR), Hospices Civils de Lyon (FR), Centre Hospitalier Universitaire de Reims (FR), Bordeaux Population Health (FR), Unité de Recherche sur les Maladies Infectieuses et Tropicales Emergentes (FR), Institut de Recherche en Santé, Environnement et Travail (FR), Centre Hospitalier Universitaire de Poitiers (FR), Centre Hospitalier Universitaire d'Angers (FR), Centre Hospitalier Universitaire de Caen Normandie (FR), Hôpital l'Archet (FR), Centre Hospitalier Universitaire de Limoges (FR), Centre Hospitalier Universitaire de Clermont-Ferrand (FR), Centre d'Immunologie et des Maladies Infectieuses (FR), Centre Hospitalier Régional Universitaire de Brest (FR), Institut Pierre Louis d‘Épidémiologie et de Santé Publique (FR), Hôpitaux Universitaires de Strasbourg (FR), Laboratoire Rhéologie et Procédés (FR), Centre Hospitalier Universitaire de Rouen (FR), Systèmes d’élevage méditerranéens et tropicaux (FR), Institut de Recherche pour le Développement (FR), Aliments Bioprocédés Toxicologie Environnements, Université de Rennes (FR), Université de Rouen Normandie (FR), Université de Lorraine (FR), Université de Reims Champagne-Ardenne (FR), Université de Caen Normandie (FR)
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